Pharmacology Fundamentals Flashcards

A patient is prescribed warfarin. Which enzyme system is primarily responsible for its metabolism?

Answer: CYP2C9

Warfarin is primarily metabolized by CYP2C9, making it susceptible to interactions with CYP2C9 inhibitors or inducers.

A drug has a therapeutic index of 2. Which statement best describes this drug?

Answer: It has a narrow safety margin between therapeutic and toxic doses

A therapeutic index of 2 means the toxic dose is only twice the effective dose, indicating a narrow safety margin requiring close monitoring.

Which pharmacokinetic parameter describes the fraction of an administered dose that reaches systemic circulation unchanged?

Answer: Bioavailability

Bioavailability (F) is the fraction of administered drug that reaches systemic circulation in its active form.

A patient taking phenytoin starts rifampicin. The nurse should anticipate which change?

Answer: Reduced phenytoin levels due to enzyme induction

Rifampicin is a potent CYP enzyme inducer that accelerates phenytoin metabolism, lowering its plasma levels.

Which receptor type uses a G-protein coupled mechanism to mediate its intracellular effects?

Answer: Beta-adrenergic receptor

Beta-adrenergic receptors couple to Gs proteins, activating adenylyl cyclase and increasing intracellular cAMP.

A drug is described as having zero-order kinetics. What does this mean clinically?

Answer: A constant amount of drug is eliminated per unit time regardless of concentration

Zero-order kinetics means saturable elimination mechanisms are overwhelmed, so a fixed amount (not a fixed fraction) is removed per unit time.

Which route of drug administration completely bypasses first-pass hepatic metabolism?

Answer: Intravenous

Intravenous administration delivers drug directly into systemic circulation, entirely bypassing hepatic first-pass metabolism.