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Introduction to Pharmacology

By Prof. Dr. Shah Murad

shahmurad65@gmail.com

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Pharmacology deals with all aspects of

drug/medicine/chemical

compounds,including their

source,effects,side

effects,permeability,distribution,metabolism

,mode of action, elimination/excretion in

the body.

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Drug/Medicine

Chemical compound used for prevention,

diagnosis and cure of diseases

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Therapeutics term is used often for cure of disease by drugs

Therapeutic’s alternate term is used

“chemotherapy” but it is commonly

applied to cytotoxic/anti-tumor drugs

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General terms used in Pharmacology

Pharmacokinetics Pharmacodynamics Pharmacotherapeutics Toxicology Pharmacy Posology Pharmaceutics Pharmacognosy Pharmacogenetics

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Drug nomenclature

Chemical name

Non-proprietary name (0fficial name)

Proprietary(Brand) name

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Essential drug concept

W.H.O has defined essential drugs as “those

chemical compounds that satisfy priority health

care needs of the population”

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Orphan drug

Biological products for

diagnosis,treatment,prevention of a rare disease or

condition for which there is no reasonable

expectation that the cost of developing and

marketing it will be recovered from the sales of

that drug,e.g. sodium nitrate,potassium

sulfate,calcitonin,digoxin immune,liothyronine(T3)

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ORPHAN DRUG

With a single diagnosed patient only, ribose-5-phosphate isomerase deficiency is presently considered the rarest genetic disease.

No single cutoff number has been agreed upon for which a disease is considered rare. A disease may be considered rare in one part of the world, or in a particular group of people, but still be common in another.

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Factors governing choice of route of drug administration

Physical and chemical properties of the

drug(solid/liquid/gas;solubility,stability,pH) Site of desired action Rate and extent of absorption of the drug from

different routes Effect of digestive juices and first pass

metabolism on the drug Rapidity with which the response is desired Accuracy of dosage required Condition of the patient

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Special features of transdermal drug delivery system

These are devices in form of adhesive patches of various shapes and sizes,which deliver the contained drug at a constant rate into systemic circulation.

The drug is held in a reservoir between an occlusive backing film and a rate controlling micropore membrane,the under surface of which is smeared with an adhesive impregnated with priming dose of drug that is protected by another film to be peeled off just before application.

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1st Pharmacokinetic Effect of Drug

It is transport of drug across biological

membranes. Drugs are transported across the membranes

by (a)Passive diffusion and filtration (b) specialized transport.

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Influence of pH on passive diffusion

Most drugs are weak electrolytes, i.e. their ionization is pH dependent(contrast to strong electrolytes---which are nearly completely ionized at acidic as well as alkaline pH).

Ions being lipid insoluble ,do not diffuse and a pH difference across a membrane can cause differential distribution of weakly acidic and weakly basic drugs on the 2 sides.

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Fate of drug after its absorption

It will bound to plasma protein……inactive form

Free (unbound) form of drug will go to its site of

action or to storage tissue. It may excrete out in

unchanged form or 1st it may be metabolized,then

excreted out by excretory organs.

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Pharmacokinetic difference between formal tissues and brain Usual capillaries have large intercellular

pores through which even large lipid

insoluble molecules diffuse.

Tight junctions in brain capillary and glial

cell processes/choroidal epithelium don’t

allow passage of non-lipid soluble

molecules/ions.

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Bioavailability,plasma concentration and therapeutic concentration of drug

Some drugs absorb slowly…exhibiting small

AUC and some have large AUC accordingly.

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Control release (CR) drugs

Usually 30% of the dose of CR-drug outside

the semipermeable membrane is released

immediately.

70% of the dose is released slowly through

the membrane over the next 4-8 hours.

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