Pharmacology Fundamentals Flashcards
7 cards from real ABFAS 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 Fundamentals flashcards as text
Which antibiotic mechanism is shared by fluoroquinolones such as ciprofloxacin?
Answer: Inhibition of DNA gyrase and topoisomerase IV
Fluoroquinolones inhibit bacterial DNA gyrase (topoisomerase II) and topoisomerase IV, preventing DNA replication and transcription.
A patient with chronic kidney disease (CrCl 25 mL/min) requires antibiotic therapy. Which agent requires the most significant dose reduction?
Answer: Cephalexin
Cephalexin is primarily renally excreted; dose intervals must be extended in renal impairment to prevent accumulation and toxicity.
Which phase I metabolic reaction is responsible for converting prodrugs such as codeine to their active form?
Answer: O-demethylation by CYP2D6
CYP2D6-mediated O-demethylation converts codeine to morphine; poor metabolizers receive no analgesic effect while ultra-rapid metabolizers risk toxicity.
What is the primary reason bisphosphonates (e.g., alendronate) must be taken on an empty stomach with a full glass of water?
Answer: To minimize esophageal irritation and improve oral bioavailability (<1%)
Bisphosphonates have extremely low oral bioavailability (<1%) that is further reduced by food, and they cause esophageal ulceration if not taken correctly.
Which mechanism explains why probenecid increases serum levels of penicillin-class antibiotics?
Answer: Probenecid competes with penicillins for renal tubular secretion via OAT transporters
Probenecid blocks organic anion transporters (OAT1/OAT3) in the renal proximal tubule, reducing tubular secretion of penicillins and prolonging their half-life.
A patient develops peripheral neuropathy after prolonged metronidazole therapy for a chronic foot wound infection. What is the threshold duration that significantly increases this risk?
Answer: More than 6 weeks
Peripheral neuropathy from metronidazole is associated with cumulative dosing and courses exceeding 6 weeks; it may be irreversible in some patients.
Which drug interaction is most clinically relevant when a patient on a fluoroquinolone takes an antacid containing aluminum or magnesium?
Answer: Chelation in the gut significantly reduces fluoroquinolone absorption
Divalent and trivalent cations (Al3+, Mg2+, Ca2+, Fe2+) chelate fluoroquinolones in the GI tract, forming insoluble complexes that drastically reduce absorption.