receptors and therapeutic index

pop1 exam 3

pharmacokinetics is the study of

the action of the body on the drug (absorption, elimination, metabolism), and dose concentration

pharmacodynamics is the study of

the action of the drug on the body and concentration effect (toxicity, effectiveness)

what is a drug receptor/target

cellular macromolecular complex that drugs interact with to elicit a cellular response

drug-receptor interactions are the determinants of

therapeutics and toxic effects of the drugs

receptors determine

the quantitative relationship between the dose and the pharmacological effect

receptors are responsible for

the selectivity of the drug action

drug receptors can consist of

proteins that regulate endogenous ligands, enzymes, nucleic acids, or complex polysaccharides

what is an inverse agonist

drugs that stabilize receptors that exhibit constitutive activity into their inactive confirmation

what is EC50

the concentration of drug that produces 50% of the maximal response

when does the dose/concentration response curve achieve its maximal asymptomatic value

when the drug occupies all of its receptors

what is affinity

ability of a drug to bind to a receptor

what is efficacy

the maximal response that a drug can produce

what is potency

the amount of a drug required to obtain a desired effect

affinity in relation to dose-concentration curve

nearer to Y axis → greater affinity

efficacy in relation to dose-concentration curve

height of the curve represents efficacy

potency in relation to dose-concentration curve

closer to y axis → greater potency

what is an agonist

drug that binds to a receptor → alters its conformation → activates the receptor’s function → biological response

possesses both affinity and efficacy

what is an antagonist

drug binds receptor and prevents activation of the receptor

what is a full agonist

drug with maximal efficacy

what is a partial agonist

drug with less than maximal efficacy

what is low intrinsic activity

drug that may act as an agonist or an antagonist

antagonists have affinity but no

efficacy

competitive antagonist

competes with an agonist for the same receptor site → decreases agonist potency and affinity but maximal response is not effected

non-competitive antagonist

acts on different site from the agonist but still prevents agonist from activating its receptors

potency is not affected, but maximal response is decreased

agonists have

affinity AND intrinsic activity

antagonists have

affinity AND no intrinsic activity

partial agonist has

affinity AND decreased intrinsic activity

is a drug with the highest potency the most beneficial therapy

not necessarily because it could still have low efficacy

what is ED50

median effective dose

dose at which 50% of the population manifests a given effect

what is TD50

median toxic dose

dose at which 50% of the population manifests a given toxic effect

what is LD50

median lethal dose

dose which kills 50% of the subjects

therapeutic index can vary from

1.0 (some cancer drugs) to >1000 (penicillin)

drugs acting on the same receptor or enzyme system often have the same

therapeutic index

large therapeutic index means the drug is

less toxic (think penicillin)

small therapeutic index means the drug is

more toxic (think cancer drugs)

what is therapeutic index

ratio of the dose that produces toxicity to the dose that produces a clinically desired or effective response