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Pharmacokinetics. Dr. M. Yulis Hamidy, MKes, MPdKed. Definition. Pharmacodynamics = the effects of the drug on the body Pharmacokinetics = the way the body affects the drug with time absorption distribution biotransformation / metabolism excretion of drugs. Passage of drugs through body.
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Pharmacokinetics Dr. M. Yulis Hamidy, MKes, MPdKed
Definition • Pharmacodynamics=the effects of the drug on the body • Pharmacokinetics = the way the body affects the drug with time • absorption • distribution • biotransformation / metabolism • excretion of drugs
Passage of drugs through body • Administration • Absorption • Distribution • Metabolism • Excretion
Drug Administration parental, oral, topical Plasma Compartment Bound Free drug drug Excretion urine, feaces, expelled air Storage fat, cytoplasm, bone Metabolism liver, GIT, lung Site of drug action
Routes of administration • Oral • Parental • Topical • buccal • vaginal • anal • dermal • ocular • nasal First pass metabolism
Plasma levels after different routes of administration IV Oral Topical Plasma concentration Time (hrs)
Drug Distribution • molecular size • lipophilicity • plasma binding • blood flow to different organs • lean:fat body weight
pKa of drug and pH of environment distribution
Plasma binding distribution
Blood Flow distribution
Metabolism • most drugs • Phase 1 • Phase 2 • ind/inh • tissues • prodrugs
Elimination • First order • zero order • intermediate
Pharmacokinetics • One-compartment model
Age, Sex, Race • Age • infants • children • elderly • Sex • Race
Drug Interactions • pharmacokinetic basis • pharmacodynamic basis
Effect of Disease on Drug Action • cardiovascular disease • liver function • celiac disease • viral infections • renal disease • asthma • Alzheimer-type dementia
Bioavailability • Bioavailability is defined as the fraction of unchanged drug reaching the systemic circulation following administration by any route. • The area under the blood concentration-time curve (area under the curve, AUC) is a common measure of the extent of bioavailability for a drug given by a particular route. • For an intravenous dose of the drug, bioavailability is assumed to be equal to unity. For a drug administered orally, bioavailability may be less than 100% for two main reasons—incomplete extent of absorption and first-pass elimination.