drug elimination and efficacy vs. potency

Question 1

zero order elimination: definition, graph, examples

Answer 1

rate of elim is constant regardless of the concentration- a fixed amount of drug is elimiated. concentration decr. linearly with time. key examples: phenytoin, ethanol, and toxic high aspirin doses

Question 2

What should I know about urine pH and drug elimination

Answer 2

ionized species are trapped in urine, while neutral species may be reabsorbed

Question 3

weak acidic drugs and urine: examples, when are they trapped, overdoses

Answer 3

phenobarbitol, methotrexate, and aspirin. they are trapped in basic environment. treat overdose with bicarb.

Question 4

weakly basic drugs and urine: examples, when are they trapped, and overdoses

Answer 4

examples: amphetamines. trapped in acidic environments. treat overdoses with ammonium chloride.

Question 5

drug metabolism phase I

Answer 5

reduction, oxidation, hydrolysis with P-450 system usually leaves slightly polar water soluble metabolites that are often still active. geriatric patients loose this stage of metabolism first.

Question 6

drug metabolism phase II

Answer 6

conjugation (glucuronidation, acetylation, and sulfation) usually yields highly polar inactive metabolites. these drugs are renally excreted. geriatric patients are still able to do phase II drug metabolism. slow aceylators often have greater side effects from certain drugs bc of decr. metab.

Question 7

Efficacy

Answer 7

maximal effect that a drug can produce. parital agonists have less efficacy than full agonists

Question 8

Potency

Answer 8

the amt of drug needed for a given effect. high potency drugs have a greater affinity for their receptors (think of chemo drugs, BP drugs, and cholesterol drugs)

Question 9

How will a competitive antagonist change a receptor binding curve?

Answer 9

curve will be shifted to the right, as affinity decreases. this indicates reduced potency without a change in efficacy. it can be overcome by incr. conc. of the agonist substrate

Question 10

How will a non-competitive antagonist change a receptor binding curve?

Answer 10

it will decrease the efficacy of the drug. it cannot be overcome by incr. agonist substrate concentration

Question 11

How will a partial agonist change a receptor binding curve

Answer 11

acts at at the same site as a full agonist, but with lower maximal effect (decr. efficacy). potency is an independent variable