Question

1A. Describe the phases of pharmacokinetics: Absorption, Distribution, Metabolism, Excretion. (ATI and Pharm book).

Answer 1

1) Four Phases of pharmacokinetics :-

- Stage 1 - Absorption

process by which drug molecules move from their site of admin to blood; determins onset of drug action; more rapid absorption, faster onset of drug; abosrption also determines intensity of drug action, each having specific % of drug absorbed; drugs w/higher absorption rates produce more effective response as long as everything else is equal.

- Stage 2 - Distribution

transportation of drugs throughout body after absorption; drugs are not passive agents, being swept along inert path to target tissues, they may interact w/blood componenets and may be chemically and physically changed before they reach target.

- Stage 3 - Metabolism

chemical process which cahnges drug molecules (how they are broken down and secreted), primary site is LIVER but also kidneys and cells in intestines; changes to drug structure allow for excretion (lipid sol to water sol); functional changes in liver or kidneys can alter pharmacological activity (metabolites may be more toxic); most drugs when metabolized have less pharm activity than original (exeptions codeine which is converted to morphine which has greater activity); PRODRUGS have no pharm activity until they undergo metabolism (enalipril - antihypertensive, benazepril, losartain).

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