Tablets I

Dr Afendi Dahlan

Overview

• Introduction to Tablet

• Advantages of Tablets

• Disadvantages of Tablets

• Types of Tablet

Introduction to Tablet

• Common delivery route of administration– Systemic or local action

• Common dosage form• Terminology: Small disc-like• Technology patented in 1843• EP definition:

– Solid preparations each containing a single dose of one or more active ingredients & usually obtained by compressing uniform volume of particles

Introduction to Tablet

• Usually oral administration– Swallowed whole– Chewed– Dissolved prior to ingestion– Retained in mouth

• Different types of use & excipients used

Advantages of Tablets

• Ease of administration• Greater stability (cf. liquid)• Dosing accuracy• Controlled release & site targetting• Taste-masking• Formulation of more than one active pharmaceutical

ingredient (“API”)• Product identification• Ease of handling & preparation• Relatively inexpensive• Consistent quality

Disadvantages of Tablets

• Low bioavailability for poorly water-soluble drugs

• Local irritant effects (eg. NSAIDs)

• Product loss during manufacturing

• Dependence on physiological factors

• Trouble in swallowing (eg. children, elderly)

Types of Tablets

• Oral tablets for ingestion– Swallowed intact with sufficient amount of

water

• Tablets used in the oral cavity– Release of API locally in oral cavity

• Tablets administered by other routes

• Tablets used to prepare solution

Oral Tablets for Ingestion

• Standard compressed tablets

• Multiple compressed tablets

• Modified release tablets

• Delayed action tablets

• Targeted tablets

• Chewable tablets

• Dispersible tablets

Standard Compressed Tablets

• Standard uncoated tablets

• Disintegrating tablets with excipients: filler, disintegrant, binder, glidant, lubricant and antiadherent.

• Process: Tablet disintegration > drug dissolution > drug absorption

• Can act locally or systematically by varying the solubility

Multiple Compressed Tablets

• The tablets in this category are prepared for two reasons: – To separate physically or chemically incompatible ingredients; and– To produce repeat action/ prolonged action tablet

• The tablet manufacturing machine is generally operated at relatively lower speed than for standard compression tablet. There are 3 categories under this class:

• Layered tablets – two to three component system

• Compression coated tablets – tablet within a tablet

• Inlay tablet – coat partially surrounding the core

• The layered tablet is preferred over compression coated tablet as the surface contact is less and the production is simple and more rapid.

Modified Release Tablets

• Diffusion-controlled release systems

• Dissolution-controlled release systems

• Erosion-controlled release systems

• Osmosis-controlled release systems

Read Aulton’s pg 458 – 461

Delayed Release Tablets• Enteric-coated tablet• Preferred when:

– API irritates gastric mucosa e.g., aspirin or strong electrolytes– Drugs that produce nausea and vomiting.– API is sensitive to low pH e.g., erythromycin– When it’s necessary to release the drug undiluted eg. intestinal antibacterial,

antiseptic agents, intestinal vermifuge, etc.

• Coating agents: – Cellulose acetate phthalate, Hydroxy methyl propyl phthalate, polyvinyl acetate

phthalate, Eudragit®

• Mechanism: – Hydration and dissolution in duodenum (pH 4 to 6) or in small intestine where pH

increases to 7 to 8 – The presence of esterases or bile salts like surface active agents plays a role in

drug release.

Targeted Tablet

• Gastro-retentive tablets– Low density tablet– Expansive tablet– Mucoadhesive polymers

• Ciprofloxacin, Diazepam, Levodopa, Benserazide

• Colonic tablets– coating with:

• pH sensitive polymer e.g., Eudragit®S100, Eudragit® L100;• biodegradable polymer like polymers which are sensitive to colonic

bacteria;• bioadhesive polymers which selectively sticks to colonic mucosa

e.g., polycarbophils or polyethans; and • redox sensitive polymers that respond to redoxv potential in colon

which expresses the total metabolic and bacterial action.

Chewable Tablet

• Alternative for children or patients with dysphagia

• Can be taken without water

• Antacid for rapid relief

• Multivitamin tablets for daily dosing

• Similar composition like conventional tablet except disintegrant not included

Dispersible Tablet

• These tablets disintegrate either rapidly in water, to form a stabilized suspension, or disperse instantaneously in the mouth to be swallowed without the aid of water

• Faster onset of action as compared to standard compressed tablet.

• The properties of the water dispersible tablet, are necessary to investigate during manufacturing which decides the product performance.

• The common examples of API formulated in this dosage form are analgesics e.g., aspirin, ibuprofen, etc.

Tablets used in the Oral Cavity

• Lozenges & Troches

• Sublingual tablets

• Buccal tablets

• Dental cones

• Mouth dissolved tablets

Lozenges & Troches

• The tablet is a flat faced at least about 18mm indiameter and meant to suck and dissolves in the mouth

• The compressed tablet is called troches and the tablets produced by fusion or candy molding process are called lozenges

• Flavours and sweeteners are added to make tablets palatable

• The tablet generally contains sucrose or lactose and gelatin solution to impart smooth taste

• Lozenges for local action in mouth/ throat are: antiseptics, antibiotics, demulcents, antitussive agents or astringents.

• To produce systemic action: multivitamin tablet.

Sublingual Tablet

• Placed under the tongue and produce immediate systemic effect by enabling the drug absorbed directly through mucosal lining of the mouth beneath the tongue

• The tablets are usually small and flat, compressed lightly to keep them soft

• Eg. GTN, Isoprinosine sulphate

Buccal Tablet

• Completeness of drug absorption is desired but fast drug absorption is not intended

• The tablets are designed not to disintegrate• They are flat elliptical or capsule shaped tablets

as it can be easily held between gum and cheek • It’s placed near the opening of parotid duct to

provide the medium to dissolve the tablet• Hormone replacement & antifungal therapy

Mouth Dissolved Tablets

• Also known as rapid-melt tablet• Used when fast relief is required eg. migraine• The tablets are designed to disintegrate as well

as dissolve within one minute or some within 10 seconds of oral administration in limited quantity of saliva

• They liquefy on tongue and patient swallows the liquid, without the need of water

Tablets administered by other routes

• Vaginal tablets

• Implants

Tablets used to prepare solution

• Effervescent tablets

• Hypodermic tablets

• Soluble tablets

Effervescent Tablets

• Dropped into a glass of water before administration and the drug solution is to be drunk immediately

• The tablet is quickly broken apart by internal liberation of CO2 in water due to interaction between tartaric acid and citric acid with alkali metal carbonates or bicarbonates in presence of water

• Advantages: an opportunity for formulator to improve taste, a more gentle action on patient’s stomach and marketing aspects

• Prepared by direct compaction and by compaction via granulation

Effervescent Tablets

• Water soluble lubricants are used to prevent an insoluble scum formation on water surface

• To add sweetness to the formulation, saccharin is added since sucrose is hygroscopic and add too much of bulk to the tablet

• The manufacturing shall be done under controlled climatic condition to avoid effervescent reaction

• The packaging is done under 25% RH at 25ºC

Hypodermic Tablets

• These tablets contain one or more readily water soluble ingredients and are intended to be added in water for injection of sterile water to form a clear solution which is to be injected parenterally

• They were widely used by rural physician due to its portability

Soluble Tablets

• Soluble tablets are uncoated or film-coated tablets

• They are intended to be dissolved in water before administration

• The solution produced may be slightly opalescent due to the added excipients used in the manufacture of the tablets

Questions

• What are the advantages and disadvantages of a direct compressed tablet?

• What is the difference between effervescent and soluble tablets?

• What is the problem with the long-term use of sublingual tablets?