5. Introduction JIS

Chapter.1 Introduction

NIMS Institute Of Pharmacy, NIMS University Jaipur Page 1

1) INTRODUCTION

1.1 Introduction to epilepsy:-

Epilepsy (from the Ancient Greek ἐπιληψία (epilēpsía) — "to seize") is a common chronic

neurological disorder characterized by seizures. These seizures are transient signs and/or

symptoms of abnormal, excessive or synchronous neuronal activity in the brain.

About 50 million people worldwide have epilepsy, and nearly two out of every three new

cases are discovered in developing countries Epilepsy is more likely to occur in young

children or people over the age of 65 years; however, it can occur at any time.

As a consequence of brain surgery, epileptic seizures may occur in recovering patients.

Epilepsies are classified in five ways:

1. By their first cause (or etiology).

2. By the observable manifestations of the seizures, known as semiology.

3. By the location in the brain where the seizures originate.

4. As a part of discrete, identifiable medical syndromes.

5. By the event that triggers the seizures, as in primary reading epilepsy or musicogenic

epilepsy

Epilepsy is usually controlled, but cannot be cured with medication, although surgery may be

considered in difficult cases. However, over 30% of people with epilepsy do not have seizure

control even with the best available medications.

Not all epilepsy syndromes are lifelong – some forms are confined to particular stages of

childhood. Epilepsy should not be understood as a single disorder, but rather as syndromic

with vastly divergent symptoms but all involving episodic abnormal electrical activity in the

brain.



1.2 Introduction to delivery system :-

The oral route of drug administration is the most popular and successfully used for

conventional delivery of drugs. It offers the advantages of convenience, ease of

administration, greater flexibility in dosage form design, ease of production, and low cost.

The parenteral route of administration is important in case of emergencies, while the topical

route of drug administration recently employed to deliver drug to the specific part of the body

for systemic effect.

It is probable that almost 90% of all the drugs are administered by oral route. Tablets are solid

preparations each containing a single dose of one or more active substances and usually

obtained by compressing uniform volumes of particles. Tablets are intended for oral

administration. Some are swallowed whole, some after being chewed, some are dissolved or

dispersed in water before being administered and some are retained in the mouth where the

active substance is liberated.

The particles consist of one or more active substances with or without excipients such as

diluents, binders, disintegrating agents, glaidants, lubricants, substances capable of modifying

the behaviour of the preparation in the digestive tract, colouring matter authorized by the

competent authority and flavouring substances.

The dosage form available for oral administrations are solutions, suspensions, powders,

tablets and capsules. The physical state of most of the drugs being solid, they are administered

in solid dosage form.

The drugs administered by oral route are versatile, flexible in dosage strength, relatively

stable, present lesser problem in formulation and packaging and are convenient to

manufacturer, store, handle and use. Solid dosage forms provide best protection to drugs

against temperature, light, oxygen and stress during transportation.1-3

Advantages of tablets

They are unit dosage form, and they offer the capabilities of all oral dosage forms for

the dose precision and the least content variability during dosing

Accuracy and uniformity of drug content

Optimal drug dissolution and hence, availability from the dosage form for absorption

consistent with intended use (i.e., immediate or extended release).

Usually taken orally, but can be administered sublingually, rectally or intravaginally.



Their cost is lowest of all oral dosage forms

They are the most compact of all oral dosage forms

They are in general the easier and cheaper to package and ship as compare to other

oral dosage forms

Product identification is simple and cheap, requiring no additional processing steps

when employing an embossed or monogrammed punch face

They are ease to administer, does not require a specialist

They are better suited to large-scale production than other unit oral forms

They have the better properties of chemical, mechanical and microbiological

stability1,4,6

Disadvantages

Some drugs resist compression, due to their amorphous nature or low-density

Drugs having bitter taste, objectionable odour or drugs that are sensitive to oxygen may

require encapsulation or coating of tablet

Bioavailability problems.

Chance of GI irritation caused by locally high concentrations medicament.

Difficulty in swallowing tablets in a small proportion of people and so size and shape

become important considerations.

Slow onset of action as compared to parenteral and solution2

Types and Classes of Tablets

Tablets are classified by their route of administration or functions

1. Oral tablets for ingestion

Compressed tablets or standard compressed tablets

Multiple compressed tablets (MCT)

a) Layered tablets

b) Compression coated tablets

Repeat action tablets

Extended release or modified release tablets

Delayed action or enteric-coated tablets

Film coated tablets

Chewable tablets



2. Tablets used in oral cavity

Buccal tablets

Sublingual tablets

Troches and lozenges

Dental cones

3. Tablets administered by other routes

Implantation tablets

Vaginal tablets

4. Tablets used to prepare solutions

Effervescent tablets

Dispersible tablets

Hypodermic tablets

Tablet triturate1-3



1.2.1 Introduction To Extended release:-

Conventional drug therapy requires periodic doses of therapeutic agents. These agents are

formulated to produce maximum stability, activity and bioavailability. For most unstable or

toxic and have narrow therapeutic ranges. Some drugs also possess solubility problems. In

such cases, a method of continuous administration of therapeutic agent is desirable to

maintain fixed plasma levels as shown in Figure.1

Figure 1.2.1: Drug level verses time profile showing differences between zero order,

controlled releases, first order extended release and release from conventional tablet2

To overcome these problems, controlled drug delivery systems were introduced three decades

ago. These delivery systems have a number of advantages over traditional systems such as

improved efficiency, reduced toxicity, and improved patient convenience. The main goal of

controlled drug delivery systems is to improve the effectiveness of drug therapies.3

Simple definition of

Extended release drug system is “any drug or dosage form modification that prolongs

the therapeutic activity of the drug”4

Ideally an Extended release oral dosage form is designed to release rapidly some pre-

determined fraction of the total dose in to GI tract. This fraction (loading dose) is an amount

of drug, which will produce the desired pharmacological response as promptly as possible and

the remaining fraction of the total dose (maintenance dose) is then release at a constant rate.

The rate of the drug absorption from the entire maintenance dose into the body should equal

to the rate of the drug removal from the body by all the processes over the time for which the

desired intensity of pharmacological response is required.3, 4

The oral controlled-release



system shows a typical pattern of drug release in which the drug concentration is maintained

in the therapeutic window for a prolonged period of time (Extended release), thereby ensuring

sustained therapeutic action. Thus, the release commences as soon as the dosage form is

administered as in the case of conventional dosage forms. Controlled drug delivery is delivery

of drug at a rate or at a location determined by needs of body or disease state over a specified

period of time.

Ideally two main objectives exist for these systems: Spatial delivery, which is related to the

control over the location of drug release. Temporal drug delivery, in which the drug is

delivered over an extended period of time during treatment.4,5

1.2.1.1 Disadvantages of conventional drug delivery system

Inconvenient

Difficult to monitor

Careful calculation necessary to prevent overdosing

Large amounts of drug can be ―lost‖ when they don’t get to the target organ

Drug goes to non-target cells and can cause damage

Expensive (using more drug than necessary).6

1.2.1.2 Advantages of controlled drug delivery system

Avoid patient compliance problems.

Employ less total drug.

Minimize or eliminate local rate effects.

Minimize or eliminate systemic side effects.

Obtain less potentiation or reduction in drug activity with chronic use.

Minimize drug accumulation with chronic dosing.

Improve efficiency in treatment

Cure or control condition more promptly.

Improve control of condition, i.e., reduce fluctuation in drug level.

Improve bioavailability of some drugs.

Make use of special effects, e.g. sustained-release aspirin for morning relief of arthritis

by dosing before bedtime

Economy. 3,6,7

1.2. 1.3Disadvantages of controlled drug delivery system

Decreased systemic availability in comparison to conventional dosage forms.



Poor in vitro - in vivo correlation.

Possibility of dose dumping due to food, physiologic or formulation variables,

chewing or grinding of oral formulations by the patient

Increased risk of toxicity

Retrieval of drug is difficult in case of toxicity, poisoning or hypersensitivity

reactions.

Higher cost of formulation3,6,7,8

1.2.1.4. Terminology

The conventional dosage forms are immediate release type. Non-immediate release delivery

systems may be divided conveniently into three categories:

Delayed Release

Extended release

Controlled Release

Prolonged Release

Site-specific and Receptor release

Organ targeting

Cellular targeting

Sub cellular targeting7-11

1. Delayed release

Delayed release systems are those systems that use repetitive, intermittent dosing of a drug

from one or more immediate release units incorporated into a single dosage form. Examples

of delayed release system include repeat action tablets and capsules. A delayed release dosage

form does not produce or maintain uniform drug blood levels within the therapeutic range.

2. Extended release system

It includes any drug delivery system that achieves slow release of drug over an extended

period of time.

3. Controlled release system

If the system is successful at maintaining constant drug level in the blood or target tissues, it

is considered as a controlled release system



Figure1.2.2: Typical drug blood level time profiles for delayed release drug delivery by

repeat action dosage form

.

4. Prolonged release system

If without maintaining constant level, the duration of action is extended over that achieved by

conventional delivery; it is considered as a prolonged release system. This is illustrated in Fig.

2.3.

5. Site-specific and receptor release

It refers to targeting of a drug directly to a certain biological location. In the case of site-

specific release, the target is a certain organ or tissue, while for receptor release; the target is

the particular receptor for a drug within an organ or tissue. Both of these systems satisfy the

spatial aspects of drug delivery.

Figure1. 2.3: Drug blood level time profile showing the relationship between controlled

release-(a), prolonged release-(b), and conventional release-(c)



1.2.5. Principle of Extended release drug delivery

The conventional dosage forms release their active ingredients into an absorption pool

immediately. This is illustrated in the following simple kinetic scheme.

Figure1. 2.4: Kinetic scheme of conventional dosage form

The absorption pool represents a solution of the drug at the site of absorption, and the term

Kr, Ka and Ke are first order rate-constant for drug release, absorption and overall elimination

respectively. Immediate drug release from a conventional dosage form implies that

Kr>>>>Ka.

Alternatively speaking the absorption of drug across a biological membrane is the rate-

limiting step. For non-immediate release dosage forms, Kr<<<Ka i.e. the release of drug from

the dosage form is the rate limiting step. This causes the above Kinetic scheme to reduce to

the following.

Figure1. 2.5: Kinetic scheme of non-conventional dosage form

Essentially, the absorptive phase of the kinetic scheme become insignificant compared to the

drug release phase. Thus, the effort to develop a non-immediate release delivery system must

be directed primarily at altering the release rate.

The main objective in designing an extended release delivery system is to deliver drug at a

rate necessary to achieve and maintain a constant drug blood level. This rate should be

analogous to that achieved by continuous intravenous infusion where a drug is provided to the

patient at a constant rate. This implies that the rate of delivery must be independent of the

amount of drug remaining in the dosage form and constant over time.



It means that the drug release from the dosage form should follows zero-order kinetics, as

shown by the following equation:

Kr ° = Rate in = Rate out = Ke Cd Vd…………..

Kr° : Zero-order rate constant for drug release-Amount/time

Ke : First-order rate constant for overall drug elimination-time-1

Cd : Desired drug level in the body – Amount/volume, and

Vd : Volume space in which the drug is distributed-Liters

The value of Ke, Cd and Vd are obtained from appropriately designed single dose

pharmacokinetic study. The equation can be used to calculate the zero order release rate

constant. For many drugs, however, more complex elimination kinetics and other factors

affecting their disposition are involved. This in turn affects the nature of the release kinetics

necessary to maintain a constant drug blood level. It is important to recognize that while zero-

order release may be desirable theoretically, non-zero-order release may be equivalent

clinically to constant release in many cases.

Sustained-release systems include any drug-delivery system that achieves slow release of drug

over an extended period of time. If the systems can provide some control, whether this is of a

temporal or spatial nature, or both, of drug release in the body, or in other words, the system

is successful at maintaining constant drug levels in the target tissue or cells, it is considered a

controlled-release system.

1.2.5. Classification of sustained/controlled release systems

1.2.5.1. Extended release preparations

These preparations provide an immediate dose required for the normal therapeutic response,

followed by the gradual release of drug in amounts sufficient to maintain the therapeutic

response for a specific extended period of time. The major advantage of this category is that,

in addition to the convenience of reduced frequency of administration, it provides blood levels

that are devoid of the peak-and-valley effect which are characteristic of the conventional

intermittent dosage regimen. Extended release dosage forms are designed to complement the

pharmaceutical activity of the medicament in order to achieve better selectivity and longer

duration of action.1, 4, 11



1.2.5.2. Controlled release preparations

Although this term has been interchanged widely with Extended release preparations in the

past, recently it has become customary to restrict the latter term to oral formulations where the

mechanism of prolonged action is dependent on one or more of the environmental factors in

the gastrointestinal tract such as pH, enzymes, gastric motility etc. On the other hand, the term

controlled release dosage form usually applies to preparations that are designed for all routes

of administration and where the mechanism of prolonged action is inherent and determined

totally by the delivery system itself. Consequently, this category offers the current state-of-

the-art products where the drug release profile is controlled accurately and often can be

targeted to a special body site or a particular organ.

1.2.6. Various approaches to achieve oral controlled release systems

The oral route of administration has received the most attention so far. This is due to easy

acceptance by patients and more flexibility in the formulation. Controlled release of drugs through

oral systems can be achieved by the following methods. 3

Table1. 2.1: Types of Extended release system

Type of system Rate-control mechanism

Diffusion controlled

Reservoir system

Monolithic system

Diffusion through membrane

Water penetration

controlled

Osmotic system

Swelling system

Transport of water through semipermeable

membrane Water penetration into glossy polymer

Chemical controlled

Monolithic system

Pendant system

Ion exchange

resins

Surface erosion or bulk erosion

Hydrolysis of pendent group and diffusion from

bulk polymer

Exchange of acidic or basic drugs with the ions

present on resins.

Regulated system

Magnetic,

Ultrasound

External application of magnetic field or

ultrasound to device



1. Diffusional controlled system

The drug is dependent on rate of diffusion through an inert membrane barrier,

usually an insoluble polymer.

(a) Reservoir devices

They are characterized by a core of drug, the reservoir; surrounded by a polymeric

membrane. The nature of membrane determines the rate of drug release.

The characteristics of reservoir diffusional system are:

Core containing the drug is surrounded by polymeric membrane, which determines the

rate of drug release.

Zero-order delivery is possible.

The drug release rate is dependent on the type of polymer.

High molecular weight compounds are difficult to deliver through the devices.

Coating and microencapsulation technique can be used to obtain such device.

(b) Matrix devices

It consists of drug dispersed homogeneously in a matrix. The characteristics of matrix

diffusional systems are:

Homogeneous dispersion of solid drug in a polymer mix,

Easy to produce than reservoir devices,

High molecular weight compound are delivered through the devices,

Zero-order release cannot be obtained.

2. Dissolution controlled systems

(a) Encapsulation dissolution control

Particles, seed or granules can be coated by technique such as microencapsulation or

fluidized bed drier.

(b) Matrix dissolution control

Aqueous dispersion, congealing, spherical agglomeration techniques etc.

3. Diffusion and dissolution controlled (bioerodible)

In a bioerodible matrix, the drug is homogeneously dispersed in a matrix and it is released

either by swelling controlled mechanism or by hydrolysis or by enzymatic attack.

(a) Osmotically controlled release system



In these systems, osmotic pressure is the driving force to generate controlled release of drug.

A semi-permeable membrane surrounds the drug and osmogen mixture. The drug is released

at constant rate throughout GIT. i.e. pH independent release is obtained.

(b) Ion-exchange systems

The use of ion-exchange resin to prolong the effect of drug is based on the principle that

negatively or positively charged pharmaceuticals combine with appropriate resins to yield

poly-salt resonates.

(c) PH independent formulation

Most of the drugs are either weak bases and hence pH dependent release is observed in body

fluids. However, buffers can be added to such formulations to maintain the constant micro

environmental pH to obtain pH-independent drug release.

1.2.7. Introduction to matrix dosage form

In this type of controlled drug delivery system, the drug reservoir results from the

homogeneous dispersion of the drug particles in either a lipophilic or a hydrophilic polymer

matrix.7, 11

Figure 2.6: Matrix diffusion controlled drug delivery system

Zone 1: Un dissolved drug, glassy polymer layer.

Zone 2: Un dissolved drug, gel layer.

Gel layer thickness = Difference between erosion and swelling front position.

1.2.7.1. Introduction to hydrophilic matrix tablet

A matrix tablet is a compressed dosage form containing an active ingredient, matrix agent

plus fillers, lubricants and excipients. Matrix systems are highly resistant to release

inconsistencies and drug ―dumping‖. A hydrophilic matrix controlled release system is

relatively easy to formulate and equally important, easy to produce. It is a robust dynamic

system composed of polymer wetting, hydration and dissolution. A hydrophilic matrix,

Zone 1

Zone 2

Zone 3

Erosion front

Swelling front

Diffusion front



controlled release system is a dynamic one involving polymer wetting, polymer hydration, gel

formation, swelling, and polymer dissolution. At the same time, other soluble excipients or

drugs will also wet, dissolve, and diffuse out of the matrix while insoluble materials will be

held in place until the surrounding polymer/excipient/drug complex erodes or dissolves away.

The mechanisms by which drug release is controlled in matrix tablets are dependent on many

variables. The main principle is that the water-soluble polymer, present throughout the tablet,

hydrates on the outer tablet surface to form a gel layer (Figure 2.7).

Figure 2.7: Drug release from hydrophilic matrix tablet

Throughout the life of the ingested tablet, the rate of drug release is determined by diffusion

(if soluble) through the gel and by the rate of tablet erosion. With soluble drugs, the primary

release mechanism is by diffusion through the gel layer. With insoluble drugs, the primary

mechanism is by the tablet surface erosion.

As increasing viscosity of the polymer yields slower drug release as a stronger more viscous

gel layer is formed, providing a greater barrier to diffusion and slower attrition of the tablet,

with insoluble drugs. The fine tuning of modified release systems may be achieved by

blending of different viscosity grades of polymer where the desired dissolution rate is not

Tablet erosion:

Outer layer becomes fully

hydrated, eventually

dissolving into the gastric

fluids.

Water continues to permeate

Gel layer

Ingestion of tablet

Initial wetting:

Tablet surface wets and

Polymer begins to hydrate,

forming a gel layer, initial

Expansion of the gel layer:

Water permeates into the tablet, increasing

the thickness of the gel layer, soluble drugs

diffuse through the gel layer.

Soluble drug:

Is released primarily by

diffusion through the

Insoluble drug:

Is released primarily

through tablet erosion.



obtained with a single polymer. A fast rate of hydration followed by quick gelation and

polymer/polymer coalescing is necessary for a rate-controlling polymer to form a protective

gelatinous layer around the matrix. This prevents the tablet from immediately disintegrating,

resulting in premature drug release. Fast polymer hydration and gel layer formation are

particularly critical when formulating with water-soluble drugs and water-soluble excipients.

Hydrophilic matrix tablet using HPMC were prepared and evaluated by Sunada et al.

They found that the type and amount of HPMC could affect the release rates as well as

kinetics from the swellable matrices. Several investigators investigated the drug release rates

and release kinetics from carbomer matrix tablets. Tablets exhibiting zero-order release

mechanisms could be obtained at several different levels of concentration of different

carbomers, such as Carbopol 934P, 971P and 974P. The results indicated that drug release

from the carbomer matrix tablets could occur, both by diffusion through low micro-viscosity

pores and by a swelling-controlled mechanism. As the amount of the carbomers in their

respective formulations increased, drug release rate decreased and the release mechanism

gradually changed from anomalous type of release to the Case II transport mechanism. Other

factors responsible for the reduction in the number and/or size of low microviscosity pores,

such as higher pH that increased polymer swelling and decreased drug release, tended to shift

the release profiles towards the swelling controlled, Case II type release mechanism.

1.2.7.2. Advantages of hydrophilic matrix tablets

With proper control of manufacturing process, reproducible release profiles are possible. They

variability associated with them is slightly less than that characterizing coated release forms.

Their capacity to incorporate active principles is large, which suits them to delivery of large

doses.

1.2.7.3. Disadvantages of hydrophilic matrix tablet

For a hydrophilic extended release matrix tablet, in which the release is mainly controlled by

erosion of the swollen polymer gel barrier at the tablet surface, the presence of food may

block the pores of the matrix and inhibit the drug release rate.



The hydrophilic polymers can be arranged into three broad categories:

(1) Non-cellulose natural or semi synthetic polymer

These are products of vegetable origin and are generally used as such. Agar, alginate, guar

gum, chitosan, modified starches, are commonly used polymer.

(2) Polymers of acrylic acid

These are arranged in carbomer group and commercialized under the name of carbopol. The

major disadvantage of this type of polymer is its pH dependent gelling characteristics.

(3) Cellulose ether

This group of semi-synthetic cellulose derivatives is the most widely used group of polymer.

Non-ionic such as Hydroxypropylmethylcellulose (HPMC) of different viscosity grades are

widely used group of polymers. Non-ionic such as HPMC of different viscosity grades is

widely used.

1.2.8. Biological factors influencing oral sustained-release dosage form design

1) Biological half-life:

Therapeutic compounds with short half-lives are excellent candidates for sustained-release

preparations, since this can reduce dosing frequency.3

2) Absorption:

The absorption rate constant is an apparent rate constant, and should, in actuality, be the

release rate constant of the drug from the dosage form. If a drug is absorbed by active

transport, or transport is limited to a specific region of the intestine, sustained-release

preparations may be disadvantageous to absorptions.3

3) Metabolism:

Drugs that are significantly metabolized before absorption, either in the lumen or tissue of the

intestine, can show decreased bioavailability from slower-releasing dosage forms. Most

intestinal wall enzyme systems are saturable. As the drug is released at a slower rate to these

regions, less total drug is presented to the enzymatic process during a specific period,

allowing more complete conversion of the drug to its metabolite.3



1.2.9. Physicochemical factors influencing oral sustained-release dosage form design

1) Dose size:

In general, single dose of 0.5 – 1.0 g is considered maximal for a conventional dosage form.

This also holds true for sustained-release dosage forms. Another consideration is the margin

of safety involved in administration of large amounts of drug with a narrow therapeutic

range.3

2) Ionization, pKa, and aqueous solubility:

Most drugs are weak acids or bases. Since the unchanged form of a drug preferentially

permeates across lipid membranes, it is important to note the relationship between the pKa of

the compound and the absorptive environment. Delivery systems that are dependent on

diffusion or dissolution will likewise be dependent on the solubility of drug in the aqueous

media. For dissolution or diffusion sustaining forms, much of the drug will arrive in the small

intestine in solid form, meaning that the solubility of the drug may change several orders of

magnitude during its release. The lower limit for the solubility of a drug to be formulated in a

Extended release system has been reported to be 0.1 mg/ml.3

3) Partition coefficient:

Compounds with a relatively high partition coefficient are predominantly lipid-soluble and,

consequently, have very low aqueous solubility. Furthermore these compounds can usually

persist in the body for long periods, because they can localize in the lipid membranes of

cells.3

4) Stability:

Orally administered drugs can be subjected to both acid-base hydrolysis and enzymatic

degradation. For drugs that are unstable in the stomach, systems that prolong delivery over the

entire course of transit in the GI tract are beneficial. Compounds that are unstable in the small

intestine may demonstrate decreased bioavailability when administered from a sustaining

dosage form. 3

1.2.10. Drug selection for oral extended release drug delivery systems

The biopharmaceutical evaluation of a drug for potential use in controlled release drug

delivery system requires knowledge on the absorption mechanism of the drug form the G. I.

tract, the general absorbability, the drug’s molecular weight, solubility at different pH and

apparent partition coefficient.15



Table 1.2: Parameters for drug selection

Parameter Preferred value

Molecular

weight/ size < 1000

Solubility > 0.1 mg/ml for pH 1 to

pH 7.8

Apparent

partition

coefficient

High

Absorption

mechanism Diffusion

General

absorbability From all GI segments

Release Should not be influenced

by pH and enzymes

Table 1.3: Pharmacokinetic parameters for drug selection

Parameter Comment

Elimination half life Preferably between 0.5 and 8

h

Total clearance Should not be dose dependent

Elimination rate constant Required for design

Apparent volume of

distribution Vd

The larger Vd and MEC, the

larger will be the required

dose size.

Absolute bioavailability Should be 75% or more

Intrinsic absorption rate Must be greater than release

rate

Therapeutic concentration

Css av

The lower Css av and smaller

Vd, the loss among of drug

required

Toxic concentration Apart the values of MTC and

MEC, safer the dosage form.

Also suitable for drugs with

very short half-life.



The pharmacokinetic evaluation requires knowledge on a drug’s elimination half- life, total

clearance, absolute bioavailability, possible first- pass effect, and the desired steady

concentrations for peak and through.

1.2.11. Basic kinetics of controlled drug delivery

In order to establish a basis for discussion of the influence of drug properties and the route of

administration on controlled drug delivery, following mechanisms need a fair mention,

- Behaviour of drug within its delivery systems

- Behaviour of the drug and its delivery system jointly in the body.

The first of the two elements basically deal with the inherent properties of drug molecules,

which influence its release from the delivery system. For conventional systems, the rate-

limiting step in drug availability is usually absorption of drug across a biological membrane

such as the gastro intestinal wall.

However, in sustained/controlled release product, the release of drug from the dosage form is

the rate limiting instead; thus, drug availability is controlled by the kinetics of drug release

than absorption.16

1.2.12. Factors influencing the in vivo performance of Extended release dosage

formulations

There are various factors that can influence the performance of an extended release product.

The physiological, biochemical, and pharmacological factors listed below can complicate the

evaluation of the suitability of an extended release dosage formulation.17

Physiological

Prolonged drug absorption

Variability in GI emptying and motility

Gastrointestinal blood flow

Influence of feeding on drug absorption

Pharmacokinetic/ biochemical

Dose dumping

First- pass metabolism

Variability in urinary pH; effect on drug elimination

Enzyme induction/ inhibition upon multiple dosing



Pharmacological

Changes in drug effect upon multiple dosing

Sensitization/ tolerance

1.2.14. In vitro evaluation of Extended release formulation

The data is generated in a well-designed reproducible in-vitro test such as dissolution test. The

method should be sensitive enough for discriminating any change in formulation parameters

and lot-to-lot variations. The key elements for dissolution are: 4

a. Reproducibility of method

b. Proper choice of media

c. Maintenance of sink conditions

d. Control of solution hydrodynamics

e. Dissolution rate as a function of pH ranging from pH 1 to 8 including several intermediate

values preferably as topographic dissolution characterization.

f. Selection of the most discriminating variables (media, pH rotation speed etc.) as the basis

for dissolution test and specification.

g. Ideal in-vitro method can be utilized to characterize bio-availability of the extended

release product and can be relied upon to ensure lot-to-lot performance.4



1.3. INTRODUCTION TO DRUG:-

DRUG INFORMATION:

1.3.1 Drug profile

Formula : drug -x

Mol. Mass : 250.294 g/mol

Density :1.71 g/cm³

Melting point :148 - 150 °C

Boiling point :697.3 °C

1.3.2 Physicochemical properties& description

Off-White to pinkish crystalline powder

Solubility: Soluble in organic solvents such as ethanol, DMSO and dimethyl formamide

(solubility ≈ 20 mg/mL); slightly soluble in acetonitrile; soluble in phosphate buffered

saline at-pH7.2(solubility≈2mg/mL)

Appearance: white to slightly yellow crystalline powder

1.3.3 Pharmacokinetic data

BCS class : I, Highly soluble

Bioavailability : Rapidly absorbed

Metabolism : Hepatic

Half-life :13 hours (31% to 72% longer in renal impairment)

Excretion : 40% as conjugated metabolites into urine

Similar amount into the faeces

Routes : Oral, intravenous

Drug Category : Antiepileptic

Time to peak serum : ~4 hours

Mechanism of Action

The precise mechanism by which drug exerts its antiepileptic effects in humans remains to be

fully elucidated. In vitro electrophysiological studies have shown that drug-x selectively



enhances slow inactivation of voltage-gated sodium channels, resulting in stabilization of

hyper excitable neuronal membranes and inhibition of repetitive neuronal firing.

Drug-x binds to collapsin response mediator protein-2 (CRMP-2), a phosphoprotein which is

mainly expressed in the nervous system and is involved in neuronal differentiation and control

of axonal outgrowth. The role of CRMP-2 binding in seizure control is unknown.

1.4 Pharmacokinetics

Absorption and Bioavailability

ANTIEPILEPTIC (DRUG-X) is completely absorbed after oral administration. The oral

bioavailability of ANTIEPILEPTIC (DRUG-X) tablets is approximately 100%. Food does not

affect the rate and extent of absorption.

After intravenous administration, Cmax is reached at the end of infusion. The 30- and 60-

minute intravenous infusions are bioequivalent to the oral tablet.

Distribution

The volumes of distribution are approximately 0.6 L/kg and thus close to the volume of

total body water. ANTIEPILEPTIC (DRUG-X) is less than 15% bound to plasma proteins.

Metabolism and Elimination

ANTIEPILEPTIC (DRUG-X) is primarily eliminated from the systemic circulation by renal

excretion and biotransformation.

After oral and intravenous administration of 100 mg [14C]-drug-x approximately 95% of

radioactivity administered was recovered in the urine and less than 0.5% in the feces. The

major compounds excreted were unchanged drug-x (approximately 40% of the dose), its O-

desmethyl metabolite (approximately 30%), and a structurally unknown polar fraction

(~20%). The plasma exposure of the major human metabolite, O-desmethyl-drug-x, is

approximately 10% of that of drug-x. This metabolite has no known pharmacological activity.

Drug-x is a CYP2C19 substrate. The relative contribution of other CYP isoforms or non-CYP

enzymes in the metabolism of drug-x is not clear. The elimination half-life of the unchanged

drug is approximately 13 hours and is not altered by different doses, multiple dosing or

intravenous administrations.



There is no enantiomeric interconversion of drug-x Special Populations Renal impairment

Drug-x and its major metabolite are eliminated from the systemic circulation primarily by

renal excretion.

The AUC of ANTIEPILEPTIC (DRUG-X) was increased approximately 25% in mildly

(CLCR 50-80 mL/min) and moderately (CLCR 30-50 mL/min) and 60% in severely

(CLCR≤30mL/min) really impaired patients compared to subjects with normal renal function

(CLCR>80mL/min), whereas Cmax was unaffected. No dose adjustment is considered

necessary in mildly and moderately renal impaired subjects. A maximum dose of 300 mg/day

is recommended for patients with severe renal impairment (CLCR≤30mL/min) and in patients

with end stage renal disease. ANTIEPILEPTIC (DRUG-X) is effectively removed from

plasma by haemodialysis. Following a 4-hour haemodialysis treatment, AUC of

ANTIEPILEPTIC (DRUG-X) is reduced by approximately 50%. Therefore dosage

supplementation of up to 50% following haemodialysis should be considered. In all renal

impaired patients, the dose titration should be performed with caution.

Side effects

double vision;

suicidal thoughts

fast or pounding heartbeats, fluttering in your chest;

feeling short of breath;

fever, skin rash, swollen glands, flu symptoms;

bruising, severe tingling, numbness, pain, muscle weakness;

nausea, upper stomach pain, itching, loss of appetite, dark urine, clay-colour stools,

jaundice (yellowing of the skin or eyes); or

Lower back pain, cloudy or bloody urine, swelling, rapid weight gain, urinating less than

usual.

Less serious side effects may include:

dizziness, spinning sensation;

loss of balance or coordination;

blurred vision;



nausea, vomiting;

drowsiness, tired feeling; or

Headache.

Usual Adult Dose for Seizures:

DRUG-X can be initiated with either oral or intravenous administration.

Initial dose: 50 mg twice daily (100 mg per day). ANTIEPILEPTIC (DRUG-X) can be

increased at weekly intervals by 100 mg/day given as two divided doses up to the

recommended maintenance dose of 200 to 400 mg/day, based on individual patient

response and tolerability. In clinical trials, the 600 mg daily dose was not more effective than

the 400 mg daily dose, and was associated with a substantially higher rate of adverse

reactions.

Oral ANTIEPILEPTIC (DRUG-X) may be taken with or without food.

Usual Paediatric Dose for Seizures:

17year so fageand older ANTIEPILEPTIC (DRUG-X) can be initiated with either oral or

intravenous administration Initial dose: 50 mg twice daily (100 mg per day).

ANTIEPILEPTIC (DRUG-X) can be increased at weekly intervals by 100 mg/day given as

two divided doses up to the recommended maintenance dose of 200 to 400 mg/day, based on

individual patient response and tolerability. In clinical trials, the 600 mg daily dose was not

more effective than the 400 mg daily dose, and was associated with a substantially higher rate

of adverse reactions.

Specific Precautions and Warnings

Some warnings and precautions to be aware of prior to taking ANTIEPILEPTIC (DRUG-X)

include the following:

Studies suggest that seizure medications may increase the risk of suicide. Make sure to

watch for any usual behaviours or mood changes, and be sure your family and friends

know to keep an eye out for such problems.

ANTIEPILEPTIC (DRUG-X) can cause drowsiness, dizziness, and coordination

problems. You may want to see how ANTIEPILEPTIC (DRUG-X) affects you before

driving or operating heavy machinery.

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Rarely, ANTIEPILEPTIC (DRUG-X) can cause irregular heart rhythms. Be watchful for

symptoms of an irregular heart rhythm, such as fainting, heart palpitations, or a rapid or

slow pulse. These problems may be more likely in people with heart problems.

Seizure medications, including ANTIEPILEPTIC (DRUG-X), can cause severe allergic

reactions that can affect multiple organs in the body. Let your healthcare provider know

right away if you develop an unexplained rash, especially if it is accompanied by a fever.

As with all seizure medications, you should not suddenly stop taking ANTIEPILEPTIC

(DRUG-X), as this can cause a worsening of seizures.

ANTIEPILEPTIC (DRUG-X) has not been adequately studied in people with liver

problems. Your healthcare provider may want to monitor you more closely and might

recommend a lower ANTIEPILEPTIC (DRUG-X) dosage.

Antiepileptic(drug-x) can interact with other medications

ANTIEPILEPTIC (DRUG-X) is considered a pregnancy Category C medication. This

means that it may not be safe for use during pregnancy, although the full risks are not

currently known

It is not known if ANTIEPILEPTIC (DRUG-X) passes through breast milk in humans

Drug interactions

In Vitro Assessment of Drug Interaction

In vitro metabolism studies indicate that drug-x does not induce the enzyme activity of drug

metabolizing cytochrome P450 isoforms CYP1A2, 2B6, 2C9, 2C19 and 3A4. Drug-x did not

inhibit CYP 1A1, 1A2, 2A6, 2B6, 2C8, 2C9, 2D6, 2E1, 3A4/5 at plasma concentrations

observed in clinical studies.

In vitro data suggest that drug-x has the potential to inhibit CYP2C19 at therapeutic

concentrations. However, an in vivo study with omeprazole did not show an inhibitory effect

on omeprazole pharmacokinetics. Drug-x was not a substrate or inhibitor for P-glycoprotein.

Drug-x is a CYP2C19 substrate. The relative contribution of other CYP isoforms or non-CYP

enzymes in the metabolism of drug-x is not clear.

Since less than 15% of drug-x is bound to plasma proteins, a clinically relevant interaction

with other drugs through competition for protein binding sites is unlikely.

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In Vivo Assessment of Drug Interactions

Drug interaction studies with AEDs

Effect of ANTIEPILEPTIC (DRUG-X) on concomitant AEDs: ANTIEPILEPTIC

(DRUG-X) 400 mg/day had no influence on the pharmacokinetics of 600 mg/day valproic

acid and 400 mg/day carbamazepine in healthy subjects.

The placebo-controlled clinical studies in patients with partial-onset seizures showed that

steady-state plasma concentrations of levetiracetam, carbamazepine, carbamazepine epoxide,

lamotrigine, topiramate, oxcarbazepine monohydroxy derivative (MHD), phenytoin, valproic

acid, phenobarbital, gabapentin, clonazepam, and zonisamide were not affected by

concomitant intake of ANTIEPILEPTIC(DRUG-X) at any dose.

Effect of concomitant AEDs on ANTIEPILEPTIC (DRUG-X): Drug-drug interaction studies in

healthy subjects showed that 600 mg/day valproic acid had no influence on the

pharmacokinetics of 400 mg/day ANTIEPILEPTIC (DRUG-X). Likewise, 400 mg/day

carbamazepine had no influence on the pharmacokinetics of ANTIEPILEPTIC (DRUG-X) in

a healthy subject study. Population pharmacokinetics results in patients with partial-onset

seizures showed small reductions (15% to 20% lower) in drug-x plasma concentrations when

ANTIEPILEPTIC (DRUG-X) was co-administered with carbamazepine, phenobarbital or

phenytoin

Drug-drug interaction studies with other drugs

Digoxin

There was no effect of ANTIEPILEPTIC (DRUG-X) (400 mg/day) on the pharmacokinetics

of digoxin (0.5 mg once daily) in a study in healthy subjects.

Metformin

There were no clinically relevant changes in metformin levels following co-administration of

ANTIEPILEPTIC (DRUG-X) (400 mg/day).

Metformin (500 mg three times a day) had no effect on the pharmacokinetics of

ANTIEPILEPTIC (DRUG-X) (400 mg/day).



Omeprazole

Omeprazole is a CYP2C19 substrate and inhibitor.

There was no effect of ANTIEPILEPTIC (DRUG-X) (600 mg/day) on the pharmacokinetics

of omeprazole (40 mg single dose) in healthy subjects. The data indicated that drug-x had

little in vivo inhibitory or inducing effect on CYP2C19.

Omeprazole at a dose of 40 mg once daily had no effect on the pharmacokinetics of

ANTIEPILEPTIC (DRUG-X) (300 mg single dose). However, plasma levels of the O-

desmethyl metabolite were reduced about 60% in the presence of omeprazole.

Oral Contraceptives

There was no influence of ANTIEPILEPTIC (DRUG-X) (400 mg/day) on the

pharmacodynamics and pharmacokinetics of an oral contraceptive containing 0.03 mg

ethinylestradiol and 0.15 mg levonorgestrel in healthy subjects, except that a 20% increase in

ethinylestradiol Cmax was observed.

NONCLINICAL TOXICOLOGY

Carcinogenesis, Mutagenesis, Impairment of Fertility .There was no evidence of drug related

carcinogenicity in mice or rats. Mice and rats received drug-x once daily by oral

administration for 104 weeks at doses producing plasma exposures (AUC) up to

approximately 1 and 3 times, respectively, the plasma AUC in humans at the maximum

recommended human dose (MRHD) of 400 mg/day. Drug-x was negative in an in vitro Ames

test and an in vivo mouse micronucleus assay. Drug-x induced a positive response in the in

vitro mouse lymphoma assay.

No adverse effects on male or female fertility or reproduction were observed in rats at doses

producing plasma exposures (AUC) up to approximately 2 times the plasma AUC in humans

at the MRHD.



1.4. INTRODUCTION TO EXCEPIENT

1.4.1 Hypromellose

1 Non-proprietary Names

BP: Hypromellose

JP: Hypromellose

PhEur: Hypromellos

USP: Hypromellose

2 Synonyms

Benecel MHPC; E464; hydroxypropyl methylcellulose; HPMC;Hypromellosum;

Methocel; methylcellulose propylene glycol ether; Methyl hydroxypropylcellulose;

Metolose; MHPC; Pharmacoat; Tylopur; Tylose MO.

3 Chemical Names and CAS Registry Number

Cellulose hydroxypropyl methyl ether [9004-65-3]

4 Empirical Formula and Molecular Weight

The PhEur 6.3 describes hypromellose as a partly O-methylated and O-(2-

hydroxypropylated) cellulose. It is available in several grades. That varies in

viscosity and extent of substitution. Grades may be distinguished by appending

a number indicative of the apparent viscosity, in mPas; of a 2% w/w aqueous

solution at 208C Hypromellose defined in the USP 32 specifies the substitution

type.

By appending a four-digit number to the non-proprietary name:

E.g. hypromellose 1828.The first two digits refer to the approximate Percentage

content of the methoxy group (OCH3). The second two Digits refer to the

approximate percentage content of the hydroxypropoxy group (OCH2CH (OH)

CH3), calculated on a dried basis. It contains methoxy and hydroxypropoxy

groups conforming to the limits for the various types of hypromellose;

Molecular weight is approximately 10 000–1 500 000



5 Structural Formula:-

Figure1.4.1 structure of HPMC

Where R is H, CH3, or CH3CH (OH) CH2

6 Functional Categories

Bioadhesive material; coating agent; controlled-release agent; dispersing agent;

dissolution enhancer; emulsifying agent; emulsion stabilizer; extended-release agent; film-

forming agent; foaming agent; granulation aid; modified-release agent;

mucoadhesive; release-modifying agent; solubilizing agent; stabilizing agent;

suspending agent; sustained-release agent; tablet binder; thickening agent; viscosity-

increasing agent.

7 Applications in Pharmaceutical Formulation or Technology

Hypromellose is widely used in oral, ophthalmic; nasal, and topical Pharmaceutical

formulations .In oral products, hypromellose is primarily used as a tablet binder, in

film-coating, and as a matrix formation in extended release tablet formulations.

Concentrations between 2% a 5% w/w may be used as a binder in either wet- or

dry-granulation processes. High-viscosity grades may be used to retard the release of drugs

from a matrix at levels of 10–80% w/w in tablets and capsules. Hypromellose is also

used in liquid oral dosage forms as suspending and/or thickening agent at concentrations

ranging from 0.25–5.0 %.

Depending upon the viscosity grade, concentrations of 2–20% w/w are used for film-

forming solutions to film-coat tablets. Lower viscosity grades are used in aqueous

film-coating solutions, while Hypromellose higher-viscosity grades are used with organic

solvents. Examples of film-coating materials that are commercially

available include Any Coat C, Spectracel, Pharmacoat, and the Methocel



E Premium LV series. Hypromellose is also used as a suspending and thickening

agent in topical formulations.

Compared with methylcellulose, hypromellos produces aqueous solutions of

greater clarity, with fewer undissolved fibers present, and is therefore preferred

in formulations for ophthalmic use. Hypromellose at concentrations

between 0.45–1.0% w/w may be added as a thickening agent to vehicles for eye

drops and artificial tear solutions. It is also used commercially in Liquid nasal

formulations at a concentration of 0.1 %.

Hypromellose is used as an emulsifier, suspending agent, and Stabilizing

agent in topical gels and ointments. As a protective Colloid, it can prevent

droplets and particles from coalescing or agglomerating, thus inhibiting the

formation of sediments. In addition, hypromellose is used in the manufacture

of capsules, as an adhesive in plastic bandages, and as a wetting agent for hard

contact lenses. It is also widely used in cosmetics and food products.

10 Typical Propertie

Acidity/alkalinity pH = 5.0–8.0 for a 2% w/w aqueous solution.

Ash 41.5%

Autoignition temperature 3608C

Density (bulk) 0.341 g/cm3

Density (tapped) 0.557 g/cm3

Density (true) 1.326 g/cm3

Melting point Browns at 190–2008C; chars at 225–2308C. Glass transition temperature

is 170–1808C.

Moisture content Hypromellose absorbs moisture from the atmosphere; the amount of

water absorbed depends upon the initial moisture content and the temperature and relative

humidity of the surrounding air.

Solubility Soluble in cold water, forming a viscous colloidal solution; practically

insoluble in hot water, chloroform, ethanol (95%), and ether, but soluble in mixtures

of ethanol and dichloromethane, mixtures of methanol and dichloromethane,

and mixtures of water and alcohol. Certain grades of hypromellose are soluble in

aqueous acetone solutions, mixtures of dichloromethane and propan-2-ol,



and other organic solvents. Some grades are swellable in ethanol. Specific gravity

1.26

Viscosity (dynamic) a wide range of viscosity types are commercially

available. Aqueous solutions are most commonly prepared, although

hypromellose may also be dissolved in aqueous alcohols such as ethanol

and propan-2-ol provided the alcohol content is less than 50% w/w.

Dichloromethane and ethanol mixtures may also be used to prepare

viscous hypromellose solutions. Solutions prepared using organic solvents tend

to be more viscous; increasing concentration also produces more viscous

solutions;

To prepare an aqueous solution, it is recommended that hypromellose is dispersed

and thoroughly hydrated in about 20–30% of the required amount of water. The water

should be vigorously stirred and heated to 80–908C, and then the hypromellose

should be added. The heat source can be removed once the hypromellose has been

thoroughly dispersed into the hot water. Sufficient cold water should then be

added to produce the required volume while continuing to stir.

H 11. Stability and Storage Conditions

Hypromellose powder is a stable material, although it is hygroscopic after drying.

Solutions are stable at pH 3–11. Hypromellose undergoes a reversible sol–gel

transformation upon heating and cooling, respectively. The gelation temperature is 50–

908C, depending upon the grade and concentration of material. For temperatures below

the gelation temperature, viscosity of the solution decreases as temperature is increased.

Beyond the gelation temperature, viscosity increases as temperature is increased.

Aqueous solutions are comparatively enzyme-resistant, providing good Viscosity stability

during long-term storage.(15) However, aqueous solutions are liable to microbial

spoilage and should be preserved with an antimicrobial preservative: when

hypromellose is used as a Viscosity-increasing agent in ophthalmic solutions,

benzalkonium chloride is commonly used as the preservative. Aqueous solutions may

also be sterilized by autoclaving; the coagulated polymer must be redispersed on cooling by

shaking. Hypromellose powder should be stored in a well-closed Container, in a cool, dry

place



Table 1.4.3.: Typical viscosity values for 2% (w/v) aqueous solutions of

Methocel (Dow Wolff Cellulosics) and Metolose (Shin-Etsu Chemical

Co. Ltd.). Viscosities measured at 208C. Methocel and Metolose products

JP/PhEur/ USP designation

Table 1.3 Typical viscosity values for 2% (w/v) aqueous solutions of Methocel

Methocel product

USP 28

designa

tion

Nominal viscosity

(mPa s)

Methocel K100 Premium LVEP 2208 100

Methocel K4M Premium 2208 4000

Methocel K15M Premium 2208 15 000

Methocel K100M Premium 2208 100 000

Methocel E4M Premium 2910 4000

Methocel F50 Premium 2906 50

Methocel E10M Premium CR 2906 10 000

Methocel E3 Premium LV 2906 3





Metolose 60SH 2910 50, 4000, 10 000

Metolose 65SH 2906 50, 400, 1500,

4000 Metolose 90SH 2208 100, 400,4000,15 000



12 Incompatibilities

Hypromellose is incompatible with some oxidizing agents. Since it is non-ionic,

hypromellose will not complex with metallic salts or ionic organics to form insoluble

precipitates.

13 Related Substances

Ethylcellulose; hydroxyethyl cellulose; hydroxyethylmethyl cellulose; hydroxypropyl

cellulose; hypromellose acetate succinate; hypromellose phthalate; methylcellulose

1.4.3. Microcrystalline cellulose

1. Non-proprietary names

BP: Microcrystalline Cellulose

JP: Microcrystalline Cellulose

PhEur: Cellulose; Microcrystalline

USPNF: Microcrystalline Cellulose

2. Synonyms

Avicel PH; Cellets; Celex; cellulose gel; hellulosum microcristallinum; Celphere; Ceolus

KG; crystalline cellulose; E460; Emcocel ;Ethispheres; Fibrocel; MCC Sanaq; Pharmacel;

Tabulose; Vivapur.

3. Chemical name

Cellulose

4. Empirical formula and molecular weight

(C6H10O5) n ~36 000; where n ~ 220.

5. Structural formula



1.4.2. Microcrystalline cellulose

6. Functional category

Adsorbent

suspending agent

Tablet and capsule diluent

Tablet disintegrant.

7. Applications in pharmaceutical formulation or technology

Microcrystalline cellulose is widely used in pharmaceuticals, primarily as a binder/diluent

in oral tablet and capsule formulations where it is used in both wet-granulation and direct-

compression processes.

In addition to its use as a binder/diluent, microcrystalline cellulose also has some lubricant

and disintegrates properties that make it useful in tableting.

Microcrystalline cellulose is also used in cosmetics and food products;

Figure1.4.4:5.6 % use of concentration of MCC

Use Concentration

(%)

Adsorbent 20 – 90

Anti-adherent 5 – 20

Capsule binder /

diluent

20 – 90

Tablet disintegrate 5 – 15

Tablet binder /

diluent

20 – 90

8. Description

Microcrystalline cellulose is purified, partially depolymerized cellulose that occurs as a

white, odourless, tasteless, crystalline powder composed of porous particles. It is

commercially available in different particle sizes and moisture grades that have different

properties and applications.



9. Solubility

Slightly soluble in 5% w/v sodium hydroxide solution

Practically insoluble in water, dilute acids, and most organic solvents.

10. Typical properties



Density (true) 1.512–1.668 g/cm3

Melting point Chars at 260–2708 °C

Moisture content

Typically less than 5% w/w. However, different grades may contain varying amounts of

water. Microcrystalline Cellulose is hygroscopic.

1.4.4 Lactose


BP: Lactose

PhEur: Lactose Monohydrate

JP: Lactose Hydrate

USP-NF: Lactose Monohydrate

2. Synonyms

CapsuLac; GranuLac; Lactochem; lactosum monohydricum; Monohydrate; Pharmatose;

PrismaLac; SacheLac; SorboLac; SpheroLac; SuperTab 30GR; Tablettose.

3. Chemical name

O-b-D-Galactopyranosyl-(1!4)-a-D-glucopyranose monohydrate


C12H22O11 H2O, 360.31




1.4.3 Structure of Lactose


Dry powder inhaler carrier; lyophilisation aid; tablet binder; tablet and capsule diluent;

tablet and capsule filler.


Lactose is widely used as a filler and diluent in tablets and capsules, and to a more limited

extent in lyophilized products and infant formulas. Lactose is used as a diluent in dry-

powder inhalation. Usually, fine grades of lactose are used in the preparation of tablets by

the wet-granulation method or when milling during processing is carried out, since the

fine size allows better mixing with other formulation ingredients and utilizes the binder

more efficiently. Lactose is also used in combination with sucrose to prepare sugar-

coating solutions. It may also be used in intravenous injections. Lactose is also used in the

manufacture of dry powder formulations for use as aqueous film-coating solutions or

suspensions. Direct-compression grades are often used to carry lower quantities of drug

and this permits tablets to be made without granulation. Other directly compressible

lactose’s are spray-dried lactose and anhydrous lactose.

8. Description

Lactose occurs as white to off-white crystalline particles or powder. Lactose is odourless

and slightly sweet-tasting; a-lactose is approximately 20% as sweet as sucrose, while b-

lactose is 40% as sweet.

9. Solubility

Practically insoluble in water and most other liquids, although polacrilin resins swell

rapidly when wetted.



10. Typical properties.

Melting point 201–202 °C (for dehydrated a-lactose monohydrate)

Moisture content Lactose monohydrate contains approximately 5% w/w water of

crystallization and normally has a range of 4.5–5.5% w/w water content.

1.4.5Colloidal Silicon Dioxide


BP: Colloidal Anhydrous Silica

JP: Light Anhydrous Silicic Acid

PhEur: Silica, Colloidal Anhydrous

USP-NF: Colloidal Silicon Dioxide

2 Synonyms

Aerosil; Cab-O-Sil Cab-O-Sil M-5P ; colloidal silica ; fumed silica; fumed silicon

dioxide; Hoch disperses silicum dioxid; SAS; silica colloidalis anhydrica; silica sol; silicic

anhydride; silicon dioxide colloidal; silicon dioxide fumed; synthetic amorphous silica;

Wacker HDK.

4 Empirical Formula and Molecular Weight

SiO2 60.08

6 Functional Categories

Adsorbent; anticaking agent; emulsion stabilizer; glidant; suspending agent;

tablet disintegrate; thermal stabilizer ; viscosity-increasing agent.


Colloidal silicon dioxide is widely used in pharmaceuticals, cosmetics, and food products;

see Table I. Its small particle size and large specific surface area give it desirable flow

characteristics that are exploited to improve the flow properties of dry powders in a

number of processes such as tableting and capsule filling. Colloidal silicon dioxide is also

used to stabilize emulsions and as a thixotropic thickening and suspending agent in gels

and semisolid preparations. With other ingredients of similar refractive index, transparent



gels may be formed. The degree of viscosity increase depends on the polarity of the liquid

(polar liquids generally require a greater concentration of colloidal silicon dioxide than

nonpolar liquids). Viscosity is largely independent of temperature. However, changes to

the pH of a system may affect the viscosity; In aerosols, other than those for inhalation,

colloidal silicon dioxide is used to promote particulate suspension, eliminate hard settling,

and minimize the clogging of spray nozzles. Colloidal silicon dioxide is also used as a

tablet disintegrant and as an adsorbent dispersing agent for liquids in powders. Colloidal

silicon dioxide is frequently added to suppository formulations containing lipophilic

excipients to increase viscosity, prevent sedimentation during molding, and decrease the

release rate. Colloidal silicon dioxide is also used as an adsorbent during the preparation

of wax microspheres; as a thickening agent for topical preparations; and has been used to

aid the freeze-drying of Nano capsules and Nano sphere suspensions.

8 Descriptions

Colloidal silicon dioxide is sub-microscopic fumed silica with a particle size of about 15 nm.

It is a light, loose, bluish-white-colour, odourless, tasteless, amorphous powder

10 Typical Properties

Acidity/alkalinity pH = 3.8–4.2 (4% w/v aqueous dispersion) and 3.5–4.0 (10% w/v

aqueous dispersion) for Cab-O-Sil M-5P

Density (bulk) 0.029–0.042 g/cm3

Density (tapped) see Tables III, IV, and V.

Melting point 16008C

Moisture content see Figure 1.(12,13)

Table 1.4.5: Uses of colloidal silicon dioxide.

Use Concentration (%)

Aerosols 0.5–2.0

Emulsion stabilizer 1.0–5.0

Glidant 0.1–1.0

Suspending and thickening agent 2.0–10.0



Particle size distribution Primary particle size is 7–16 nm. Aerosil forms loose

agglomerates of 10–200 mm. See also Figure 2.

Refractive index 1.46

Solubility Practically insoluble in organic solvents, water, and acids, except

hydrofluoric acid; soluble in hot solutions of alkali hydroxide. Forms a colloidal

dispersion with water. For Aerosil solubility in water is 150 mg/L at 258C (pH 7).

Specific gravity 2.2

Specific surface area

100–400m2/g depending on grade. See also Tables III, IV, and V. Several Grades of

colloidal silicon dioxide are commercially available, which Produced by modifying the

manufacturing process. The modifications do not affect the silica content, Colloidal Silicon

Dioxide


Incompatible with diethylstilboestrol preparations

12 Related Substances

Hydrophobic colloidal silica.

1.4.6 Talc


BP: Purified Talc

JP: Talc

PhEur: Talc

USP: Talc

2 Synonyms

Altalc; E553b; hydrous magnesium calcium silicate; hydrous magnesium silicate; Imperial;

Luzenac Pharma; magnesium hydrogen metasilicate; Magsil Osmanthus; Magsil Star;

powdered talc; purified French chalk; Purtalc; soapstone; steatite; Superiore; talcum.

3. Empirical Formula and Molecular Weight

Talc is a purified, hydrated, magnesium silicate, approximating to the formula Mg6

(Si2O5)4(OH) 4. It may contain small, variable amounts of aluminium silicate and iron



4 Functional Category

Anticaking agent; glidant; tablet and capsule diluent; tablet and capsule lubricant.


Talc was once widely used in oral solid dosage formulations as a lubricant and diluent; see

Table I, although today it is less commonly used. However, it is widely used as a dissolution

retardant in the development of controlled-release products.

Talc is also used as a lubricant in tablet formulations; in a novel powder coating for extended-

release pellets; and as an adsorbant.

In topical preparations, talc is used as a dusting powder, although it should not be used to dust

surgical gloves; see Section 14. Talc is a natural material; it may therefore frequently contain

microorganisms and should be sterilized when used as a dusting powder; see Section 11. Talc

is additionally used to clarify liquids and is also used in cosmetics and food products, mainly

for its lubricant properties.

.Table 1.4.6: Uses of talc.

Use Concentration (%)

Dusting powder 90.0–99.0

Glidant and tablet lubricant 1.0–10.0

Tablet and capsule diluent 5.0–30.0

6 Descriptions

Talc is a very fine, white to grayish-white, odourless, impalpable, unctuous, crystalline

powder. It adheres readily to the skin and is soft to the touch and free from grittiness.

8 Typical Properties

Acidity/alkalinity pH = 7–10 for a 20% w/v aqueous dispersion.

Hardness (Mohs) 1.0–1.5

Moisture content Talc absorbs insignificant amounts of water at 258C and relative

humidities up to about 90%..

Particle size distribution Varies with the source and grade of material. Two typical grades

Sare≥99% through a 74 mm (#200mesh) or≥ 99% through a 44 mm (#325 mesh).



Refractive index nD 20 = 1.54–1.59

Solubility Practically insoluble in dilute acids and alkalis, organic solvents, and water.

Specific gravity 2.7–2.8

Specific surface area 2.41–2.42m2/g

9 Stability and Storage Conditions

Talc is a stable material and may be sterilized by heating at 1608C for not less than 1 hour. It

may also be sterilized by exposure to ethylene oxide or gamma irradiation.(10) Talc should be

stored in a well-closed container in a cool, dry place,


Incompatible with quaternary ammonium compounds

1.4.7Magnesium stearate


BP: Magnesium stearate

JP: Magnesium stearate

PhEur: Magnesii stearas

USPNF: Magnesium stearate

2. Synonyms

Magnesium octadecanoate; octadecanoic acid, magnesium salt, Stearic acid,

magnesium salt.

3. Chemical name

Octadecanoic acid magnesium salt.


C36H70MgO4; 591.34


[CH3(CH2)16COO]2Mg




Tablet lubricant.

Capsule lubricant.


Magnesium stearate is widely used in cosmetics, foods, and pharmaceutical

formulations.

It is primarily used as a lubricant in capsule and tablet manufacture at concentrations

between 0.25% and 5.0% w/w.

It is also used in barrier creams.

8. Description

Magnesium stearate is a very fine, light white, precipitated or milled, impalpable powder of

low bulk density, having a faint odour of stearic acid and a characteristic taste. The powder is

greasy to the touch and readily adheres to the skin.

9. Solubility

Practically insoluble in ethanol, ethanol (95%), ether and water; slightly soluble in warm

benzene and warm ethanol (95%).

10. Typical properties



Density (true) 1.092 g/cm3

Melting range 117–150°C (commercial samples); 126–130°C (high purity magnesium

stearate).

Documents

5. Introduction JIS