Pharmacist Flashcards

A patient on warfarin presents with an INR of 6.8 but no signs of active bleeding. Which is the MOST appropriate pharmacist intervention according to DHA guidelines?

Answer: Hold warfarin and administer oral vitamin K 2.5 mg immediately

For an INR of 4.5–10 with no significant bleeding, current evidence-based guidelines (reflected in DHA practice) recommend holding warfarin and administering low-dose oral vitamin K (1–2.5 mg). Oral vitamin K is preferred over IV due to the risk of anaphylaxis with IV administration. Continuing warfarin risks dangerous bleeding, and waiting without any vitamin K for an INR of 6.8 is insufficiently aggressive.

A pharmacist receives a prescription for metformin 1000 mg BD in a patient whose most recent eGFR is 28 mL/min/1.73m². What is the CORRECT action?

Answer: Contact the prescriber to recommend discontinuing metformin, as eGFR < 30 is a contraindication

Metformin is contraindicated when eGFR falls below 30 mL/min/1.73m² due to the risk of lactic acidosis from drug accumulation. The pharmacist must not dispense and should contact the prescriber to recommend an appropriate alternative. Independently substituting another agent without prescriber authorization is outside the pharmacist's scope.

Which cytochrome P450 enzyme is primarily responsible for the metabolism of clopidogrel to its active thienopyridine metabolite, making omeprazole co-prescription clinically significant?

Answer: CYP2C19

Clopidogrel is a prodrug that requires hepatic conversion to its active metabolite primarily via CYP2C19. Omeprazole is a significant CYP2C19 inhibitor, reducing active metabolite formation and thereby attenuating the antiplatelet effect. Pantoprazole has much less inhibitory effect on CYP2C19 and is preferred when a PPI is necessary alongside clopidogrel.

A 32-year-old woman who is 10 weeks pregnant presents with a UTI. Culture confirms Escherichia coli sensitive to multiple agents. Which antibiotic is MOST appropriate?

Answer: Nitrofurantoin 100 mg modified-release BD for 5 days

Nitrofurantoin is considered safe in the second trimester and is appropriate for uncomplicated lower UTI in pregnancy. Fluoroquinolones (ciprofloxacin) are contraindicated in pregnancy due to fetal cartilage effects. TMP-SMX carries risks of neural tube defects in the first trimester and neonatal hyperbilirubinemia near term. Doxycycline is contraindicated in pregnancy due to effects on fetal bone and teeth.

In the context of DHA pharmacy practice, a dispensed medication is recalled by the manufacturer due to a sterility failure. The pharmacist identifies 14 patients who received the affected lot. What is the PRIORITY first step?

Answer: Notify DHA's Pharmacy and Drug Control Department and quarantine remaining stock

Under DHA regulatory requirements, a product recall must first be reported to the DHA Pharmacy and Drug Control Department, and remaining stock must be quarantined to prevent further dispensing. Contacting patients is also necessary but occurs after regulatory notification and guidance. Disposing of stock before regulatory review destroys evidence needed for recall management. Waiting passively for the pharmacy director without notifying DHA delays mandatory regulatory reporting.

A patient stabilized on lithium carbonate 400 mg TDS is initiated on ibuprofen 400 mg TDS for 2 weeks for knee pain. Which pharmacokinetic mechanism best explains the expected drug interaction?

Answer: NSAIDs reduce renal prostaglandin synthesis, decreasing lithium renal excretion and increasing plasma levels

Lithium is renally excreted and its clearance depends on renal blood flow and tubular handling, which is prostaglandin-dependent. NSAIDs inhibit COX enzymes, reducing renal prostaglandin synthesis, which causes afferent arteriolar constriction and decreased GFR. Additionally, reduced prostaglandins enhance sodium (and lithium) reabsorption in the proximal tubule. This raises serum lithium levels, potentially causing toxicity. Lithium is not protein-bound, so displacement is irrelevant.