Intro to pharmacology
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Transcript of Intro to pharmacology
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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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