UNIT 1INTRODUCTION TO PHARMACOLOGY

MINATI DASLECTURERCOLLEGE OF NURSING KINS, KIIT UNIVERSITY,BHUBANESWAR, ODISHA

Meaning

The word pharmacology is made up of two words (greek): ‘pharmacon’ means drug and ‘logos’ means study. That means ,”it is the science that deals with the study of various drugs, their usages, doses, indications, side effects and associated interactions”.

Pharmacology is the study of drugs (chemicals) that alter functions of living organisms.

Drug therapy involves the use of drugs to prevent, diagnose or cure disease processes or to relieve signs and symptoms without caring the underlying disease.

DEFINITION

Drug: A drug is defined as the any

substance used for the purpose of diagnosis, prevention, relief or cure of a disease in men or in animals.

Pharmacology: It is the branch of science which

deals with the study of drugs, their origin, nature, properties and effects.

SOURCES OF DRUGS1. PLANTS: plants and their parts have been

used as medicines since prehistoric times naturally or processed synthetically ,e.g., digoxin , quinine, morphine etc.

2. Animals products: animals products are used to replace some human chemicals , e.g., insulin, thyroid drugs, growth hormone, heparin etc.

3. Minerals and oils: minerals e.g., aluminum, iron, fluoride, magnesium etc, their salts are used to cure many diseases. Oils like liquid paraffin is used as purgative.

4. Microorganisms: many microorganisms( bacterial and fungi) are used to prepare many drugs that are effective against some bacteria. E.g., penicillin, tetracyclines etc.

5. Humans: some drugs are prepared from human, e.g., immunoglobin from blood, growth hormones etc.

6. Products of genetic engineering: many drugs are obtained from cell culture and recombinant DNA tecnology, e.g., human insulin.

TERMINOLOGY

Analgesics: a drug that relieves pain, e.g. diclofenac sodium.

Anesthetics: an agent reduce sensation

Antacids: a drug that neutralizes the HCI acid secreted in digestives juices of stomach.

Antibiotics: a substance that destroys or inhibits the growth of bacteria and microorganisms.

Anticonvulsant: a drug that prevent or reduce seizures.

Anticoagulants: the drug that prevent the clotting of blood.

Antidotes: a drug that counteracts the effects of a poison or overdosage by another drug.

Antiemetics: an agents that prevents vomitting

Antifungal: a drug that inhibits the growth or destroy fungal organisms.

Antipyretic: the drugs which reduce fever e.g paracetamol.

Antiseptic: it is a substance that inhibit the growth and development of micro-organism without destroying them e.g savlon.

Antihistamines: a drug is used for allergic reactions. E.g -chlorphenamine

Antispasmodic:a drug which relieves the spasm of involuntary smooth muscles.e.g- Buscopan

Antitussive: a medicinal preparation for suppressing coughs. E.g- codeine.

Anti-inflammatory:the drugs which suppress inflammation.e.g- Betamethasone

Bronchodilators: the drug widen airways in lungs.e.g-salbutamol

Cathartics(laxative,purgative) : Adrug used to stimulate or increase the frequency of bowel evacuation.e.g-bisacodyl, magnesium salt.

Corticosteroids: Diuretics: Emetics: Emollient: Expectorant: an agent that facilitates

removal of broncho-pulmonary secretion, e.g- Bromohexine

Galactogogue: an agents that induces secretion of milk.

Hypnotics: a drug that produces sleep by depressing brain function .e.g.-Benzodiazepines.

Mycotic: a drug that dilate the pupil of eye. E.g- opioids, cholinergic.

Mydriatics: a drug that dilate the pupil of eye, e.g-atropine

Narcotic : a drug that induces stupor and relieve pain .e.g.morphine.

Oxytocics: a drug that stimulate uterine contraction .e.g oxytocin.

Vasodilators: a drug that causes widening of the blood vessels and increase blood flow, e.g glyceryl trinitrate.

Antirheumatic :Drugs used to treat rheumatism.

Anti –tubercular:the specific drugs used in the treatment of tuberculosis.

Anti-prurtitics: a drug that relieve itching.

Anti-phlogistic: an agent used to prevent the progress of inflammation.

Cathartics: drugs used to cause intestinal evacuation.

Cortico –steroids: hormonal drugs extracted from the adrenal cortex.

Cholagogues: drugs which are supposed to increase the amount of bile secreted.

Diaphoretics: drugs which increase the action of sweat glands and induce perspiration.

Types of pharmacology

Two types1. Experimental pharmacology: it is

done in the laboratory on experimental animals such as rodents and non-rodents.

2. Clinical pharmacology: it is the study of effects of drugs in human being.

1- EXPERIMENTAL PHARMACOLOGY It is done in the laboratory on

experimental animals such as rodents and non rodents.

2 CLINICAL PHARMACOLOGY

It is the study of effects of drugs in human being.

DIVISION OR CLASSIFICATION OF PHARMACOLOGY

Pharamacology have two main division:-

1. Pharmacodynamics(dynamics-power)

2. Pharmacokinetics( Kinetics-movement)

1-pharmacodynamics(dynamics-power)

Pharmacodynamic is the study of the effects of the drugs on the body and their mechanism of action, i.e. what drugs do to the body , in other words we can say mechanism of drug action.

Body functions are mediated through control systems that involve receptors, enzymes, carrier molecules and other specialized macrolecules such as DNA.

Mechanism of drug action, how drug acts on body by various means. some of them are as following-

a) On the cell membrane by: Action on specific receptors(example-

histamine receptors, acetylcholine receptors, ca++channel blockers)

Interference with selective passage of ions across membranes.

Inhibition of membrane bound enzymes and pumps,e.g.membrane bound ATP ase by cardiac glycoside tricyclic antidepressant block the pump by which amines are actively taken up from the exterior to the interior nerve cells.

Physicochemical interaction, (e.g. general and local anesthetics and alcohol appear to act on the lipid,protein or water constituents of nerve cell membranes.

b) Through metabolic processes within the cells by:-

Enzyme inhibition, e.g. monoamine oxidase by phenelzine, cholinesterase by pyridostigmine

Inhibition of transport process that carries substances across cells, e.g. blockage of anion transport in the renal tubule cell by probencid can be used to delay excretion of penicillin and to enhance elimination of urate.

incorporation into large molecules: e.g. fluoruracil is an anticancer drug is incorporated into messenger RNA in place of uracil.

In the case of successful antimicrobial agent, by altering metabolic process unique to microorganisms, e.g. penicillin interferes with formation of cell wall.

C) outside the cell by: direct chemical interaction, e.g. chelating

agents,antacids. Osmosis as with purgatives, e.g. magnesium

sulphate and diuretics (mannitol)d) Drug action through receptors: most

receptors are protein molecules. agonists: Drugs that activate receptors.

They do so because they resemble the natural transmitter or hormone. (e.g. activation of B-adrenoceptors by a catecholamine)

Antagonists (blockers): it is a similar to the natural agonist to be recognized by the receptor and to occupy without activating it.

2- pharmacokinetics Pharmacokinetics is the study of absorption,

distribution, metabolism and excretion of drugs i.e. the movement of the drugs into, within and out of the body.It is what the body does to the drugs.

Flow chart:- (1) absorption drug in plasma drug in (2)

Distribution tissue (3)

Metabolism (4) Elimination

I)-Absorption

Absorption is the transfer of a drug from its site of administration to the blood stream. The rate and efficiency of absorption depend on the route of administration.

Types of absorptions are:1: Transportation of drug from GI tract:- depending on their chemical properties,

drugs may be absorbed from G.I. tract by either diffusion or active transport.

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2-Oral absorption: when the drug is given oral route site is mainly absorbed through mucus membrane of mouth, stomach and intestine. Drugs is then exposed to degradative effects of enzymes in liver. Some drugs become activated in liver and are known as prodrugs.

Examples- prodrugs include: methyldopa, a drug used for hypertension in pregnancy .

3- intravenous absorption: 4- intramuscular /SC/ID Absorption: 5- Inhalation ,,: 6- topical ,,:

Factors affects drug absorption

1. Physical state 2. Particle size3. Solubility 4. area of absorbing surface 5. Circulation to site of absorption6. Route of administration

Bioavailability

Bioavailability is the fraction of administered drug that reaches the systemic circulation.

Bioavailability is expressed as the fraction of administered drug that gain access to the systemic circulation in chemically uncharged form: e.g. if 100 mg of drug is administered orally and 70 mg this is absorbed unchanged, the bioavailability is 70%.

II) DRUG DISTRIBUTION

In this process drug reversibly leaves the blood stream and enters the extracellular fluid and for the cell or the tissue.

Factors affects distribution of drug:I. Solubility of drugs: II. Route of administration III. Plasma protein binding:IV. Blood flow region V. Any barrier: like blood Brain Barrier(BBB)

III) METABOLISM OR BIOTRANSFORMATION It is the process of biochemical

alteration of the drugs in the body. By this process, a drug may either be inactivated or converted into a more active compound. Metabolism is the biochemical process, a drug is converted to ionized or polar water soluble form which is readily excreatable.

Sites of metabolism

Liver is most impotant organ for drug metabolism,it can be metabolized by kidney, lungs,GIT,Plasma and skin.

Factors influencing metabolism Age Nutrition Diseases state Enzyme induction Stress Sex Route of administration Intestinal bacterial flora Enzyme inhibition Bodt temperature.

Chemical processes involved in metabolism All chemical reaction usually

catalyzed by some enzymes. It may involve one or more of the following reaction-

oxidationHydrolysis reduction Conjugation and transfer reaction.

IV)- EXCRETION OR ELIMINATION It refers to elimination of a drug from

circulation or body. A drug may be pass out either unchanged or as its metabolites.

Excretion occurs: by the kidney via urine by the lungs via exhaled air through saliva, tears and sweat by the liver via bile and into feaces into breast milk

EX- OF ELIMINATION

Kidney are most common organs of drug removal. Glomerular filtration is most common method of drug elimination via kidneys. Some drugs like penicillin (acidic) and digoxin (basic) are eliminated by tubular secretion in proximal convoluted tubules.

Clearance (CL)

Clearance means making plasma free from drug per unit time.

It is an important pharmacokinetic concept.

CL= Rate of elimination plasma concentration

Plasma half life

It means, plasma concentration of a drug dips by half in a given time.

It is the time, necessary for concentration of drug to decrease by one half . It is denoted by t1/2.

Dosages can be calculated by following formulas:

a) Loading dose b) Maintenance dose

example

T1/2 of aspirin is about 4 hrs, if 150 mg of aspirin is given initially , then 75 mg eliminated in 1st 4 hrs, in next 4 hrs about 37 mg will be elimininated .