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PHARMACODYNAMICS: how the drug effects the body

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-studies the therapeutic and toxic effects on the organ systems of the body
-the drug effects on the body determines the drugs' efficacy, potency, and therapeutic ratio
-concerned with mechanism of action, drug interactions, and structure-activity relationships
-parameters of pharmacodynamics is better understood by studying the dose-response curves and drug receptors

Dose-response curves
-relationship between the drug dose and the pharmacologic effect on the organ systems of the body
-extrapalating information from the dose-response curve allows for the following parameters:

efficacy: the maximal pharmacological effect of a particular drug on the body
median effective dose (ED 50): dose of a given drug required to create a given effect in 50% of the population
median lethal dose (LD50): dose of a given drug that leads to death in 50% of the population
therapeutic index ratio of median lethal dose: median effective dose (LD50: ED50)

Drug receptors
-macromolecules which interacts with a drug to facilitate a charecteristic intracellular change
-mechanism of action generally depends on the drug interacting with the receptor

Agonist: endogenous and or exogenous substances which bind directly to receptors and create direct cellular changes in physiology
-endogenous agonist (ex. hormone)
-exogenous agonist (drug)

Antagonist: endogenous and or exogenous substance which bind to the receptor however do not create a direct cellular change

Competitive antagonist: reversibly binds to receptors that can be displaced by higher concentrations of agonist

Noncompetitive antagonist: irreversible binding to receptors such that even higher concentrations of agonist does not reverse blockade