Pharmacology Principles Flashcards
7 cards from real PSA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Pharmacology Principles flashcards as text
A drug with a half-life of 6 hours is started at regular dosing intervals. Approximately when will it reach steady-state plasma concentration?
Answer: After 4-5 half-lives (24-30 hours)
Steady state is reached after approximately 4-5 half-lives, regardless of the dosing interval or dose size.
Which route of administration most reliably bypasses hepatic first-pass metabolism?
Answer: Sublingual tablet
Sublingual administration allows drug absorption directly into systemic circulation via the sublingual veins, bypassing the portal circulation and hepatic first-pass effect.
A drug has a volume of distribution (Vd) of 700 L. What does this indicate about the drug?
Answer: It is extensively distributed into peripheral tissues or fat
A large Vd (>100 L) indicates the drug distributes extensively into peripheral tissues or adipose tissue, with low plasma concentrations relative to total body drug.
Creatinine clearance (CrCl) is primarily used to guide dose adjustment for which category of drugs?
Answer: Drugs that are predominantly renally excreted unchanged
CrCl estimates glomerular filtration rate and is used to adjust doses of renally excreted drugs (e.g., gentamicin, metformin) to prevent accumulation and toxicity.
Why is a loading dose used when initiating therapy with certain drugs?
Answer: To rapidly achieve therapeutic plasma concentrations
A loading dose rapidly achieves therapeutic drug levels by filling the volume of distribution, which is particularly important for drugs with long half-lives where waiting for steady state would be clinically unacceptable.
A drug undergoes Phase I metabolism primarily via CYP3A4. Which Phase I reaction is most commonly catalysed by CYP enzymes?
Answer: Oxidation
CYP450 enzymes primarily catalyse oxidation reactions as Phase I metabolism, introducing or unmasking polar functional groups to facilitate drug elimination.
A patient has eGFR of 20 mL/min/1.73m². Which pharmacokinetic parameter is most directly altered for a drug that is 90% renally excreted?
Answer: Total drug clearance
Renal impairment reduces total drug clearance for renally excreted drugs, prolonging their half-life and increasing accumulation risk with standard dosing.