NAPLEX QBANK Naplex Qbank/Questions/Practice 1 — Questions and Answers
Question 1: A patient with a CrCl of 28 mL/min is currently taking metformin 1000 mg twice daily for type 2 diabetes. What is the most appropriate action?
- Continue metformin at the current dose and recheck renal function in 3 months
- Reduce the metformin dose to 500 mg twice daily
- Discontinue metformin due to risk of lactic acidosis (Correct answer)
- Switch metformin to extended-release formulation to improve renal tolerance
Correct answer: Discontinue metformin due to risk of lactic acidosis
Metformin is contraindicated when CrCl falls below 30 mL/min because impaired renal clearance leads to drug accumulation and a dangerous risk of lactic acidosis. Dose reduction is not sufficient at this level — the drug must be discontinued.
Question 2: Which antipsychotic medication requires mandatory enrollment in a Risk Evaluation and Mitigation Strategy (REMS) program due to the risk of severe agranulocytosis?
- Olanzapine
- Quetiapine
- Clozapine (Correct answer)
- Aripiprazole
Correct answer: Clozapine
Clozapine carries a black box warning for potentially fatal agranulocytosis and requires the Clozapine REMS Program, which mandates ANC monitoring before dispensing. No other antipsychotic has this requirement.
Question 3: A 58-year-old patient is started on isoniazid (INH) for latent tuberculosis. Which supplement should routinely be co-administered to prevent a common dose-dependent adverse effect?
- Vitamin B12 (cyanocobalamin)
- Vitamin B6 (pyridoxine) (Correct answer)
- Folic acid
- Vitamin D
Correct answer: Vitamin B6 (pyridoxine)
INH inhibits pyridoxine (B6) metabolism, which can lead to peripheral neuropathy, particularly in high-risk groups (elderly, malnourished, diabetic, pregnant). Pyridoxine 25–50 mg daily is co-prescribed to prevent this toxicity.
Question 4: A patient with a history of bilateral renal artery stenosis presents with newly diagnosed hypertension. Which antihypertensive class is most likely to precipitate acute renal failure in this patient?
- Dihydropyridine calcium channel blockers
- Thiazide diuretics
- ACE inhibitors (Correct answer)
- Beta-1 selective beta-blockers
Correct answer: ACE inhibitors
In bilateral renal artery stenosis, perfusion of both kidneys depends on angiotensin II–mediated efferent arteriolar constriction. ACE inhibitors block this compensatory mechanism, causing a sharp drop in GFR and acute kidney injury.
Question 5: A pharmacist is reviewing vancomycin therapy for a hospitalized patient with MRSA bacteremia. According to current ASHP/IDSA/SIDP consensus guidelines, which monitoring approach is now preferred over trough-only monitoring?
- Peak and trough levels measured at steady state
- AUC/MIC ratio-guided monitoring combined with serum creatinine (Correct answer)
- Daily random vancomycin levels regardless of timing
- Trough-only monitoring targeting 15–20 mg/L
Correct answer: AUC/MIC ratio-guided monitoring combined with serum creatinine
Current consensus guidelines (2020) replaced trough-only monitoring with AUC/MIC-guided monitoring (target AUC 400–600 mg·h/L), as it better predicts efficacy and reduces nephrotoxicity risk compared to targeting high trough levels.
Question 6: A patient taking lithium 300 mg three times daily reports new-onset coarse tremor, confusion, and vomiting. His lithium serum level is 2.1 mEq/L. What is the most appropriate immediate intervention?
- Add propranolol to manage the tremor and continue lithium
- Reduce the lithium dose by 50% and recheck level in 48 hours
- Hold lithium, provide IV hydration, and arrange emergent evaluation (Correct answer)
- Administer sodium polystyrene sulfonate to enhance lithium excretion
Correct answer: Hold lithium, provide IV hydration, and arrange emergent evaluation
A lithium level of 2.1 mEq/L with neurological and GI symptoms indicates moderate-to-severe toxicity (therapeutic range: 0.6–1.2 mEq/L for maintenance). Lithium must be held immediately, and IV normal saline is given to enhance renal clearance. Emergent evaluation for possible hemodialysis is indicated.
NAPLEX QBANK Naplex Qbank/Questions/Practice 1
A patient with a CrCl of 28 mL/min is currently taking metformin 1000 mg twice daily for type 2 diabetes.
What is the most appropriate action?