All 10 Questions With Complete Rationales
Prefer to read straight through, or want to review after taking the quiz? Every question, the correct answer, and the reasoning behind it are laid out below.
Question 1
A 58-year-old patient with diabetes and COPD presents with community-acquired pneumonia (CAP). He is treated as an outpatient. According to current IDSA/ATS guidelines, what is the preferred empiric antibiotic regimen?
A. Azithromycin monotherapy B. Amoxicillin monotherapy C. Respiratory fluoroquinolone (levofloxacin or moxifloxacin) D. TMP-SMX + macrolide
✅ Answer: C — Respiratory fluoroquinolone (levofloxacin or moxifloxacin)
Respiratory fluoroquinolone is preferred for outpatient CAP with comorbidities. IDSA/ATS 2019 CAP guidelines: Patients WITH comorbidities (diabetes, COPD, heart/liver/renal disease, malignancy, asplenia, immunosuppression) or prior antibiotic use → Respiratory FQ (levofloxacin, moxifloxacin) OR beta-lactam + macrolide. Azithromycin monotherapy is only for healthy patients without comorbidities due to resistance concerns.
Question 2
A patient with MRSA bacteremia is started on vancomycin. According to current guidelines, vancomycin monitoring should be guided primarily by which pharmacokinetic/pharmacodynamic parameter?
A. Trough concentration only (target 15–20 mcg/mL) B. AUC/MIC ratio (target AUC 400–600 mg·h/L) C. Peak concentration (target 30–40 mcg/mL) D. Random level drawn 2 hours post-infusion
✅ Answer: B — AUC/MIC ratio (target AUC 400–600 mg·h/L)
AUC/MIC-guided monitoring is now the standard. The 2020 ASHP/IDSA/SIDP Vancomycin Consensus Guidelines replaced trough-only monitoring with AUC-guided dosing. Target: AUC 400–600 mg·h/L (assuming MIC ≤1 mcg/mL). Trough-only monitoring correlates poorly with efficacy and overestimates nephrotoxicity risk. Bayesian software is preferred for AUC estimation.
Question 3
A 35-year-old woman presents with her third episode of C. difficile infection (CDI) in 6 months. She responded to oral vancomycin each time but relapsed within 4 weeks. What is the most appropriate next step?
A. Repeat oral vancomycin 125 mg four times daily for 14 days B. Intravenous metronidazole plus oral vancomycin C. Fecal microbiota transplantation (FMT) D. Oral fidaxomicin followed by metronidazole taper
✅ Answer: C — Fecal microbiota transplantation (FMT)
FMT is recommended for multiply recurrent CDI. IDSA CDI guidelines: For a 3rd or later recurrence after standard therapy, FMT is recommended (strong recommendation). FMT restores gut microbiome diversity and has 80–90% success rates for recurrent CDI. Bezlotoxumab (monoclonal antibody against CDI toxin B) can be used adjunctively to reduce recurrence risk. Repeating vancomycin has diminishing returns with each recurrence.
Question 4
A patient is started on daptomycin for MRSA. Two days later, his respiratory status worsens. A chest X-ray shows a new pulmonary infiltrate consistent with pneumonia. What is the most likely explanation?
A. Daptomycin-induced pulmonary toxicity (eosinophilic pneumonia) B. Treatment failure — daptomycin is ineffective against MRSA C. Daptomycin is inactivated by pulmonary surfactant D. Daptomycin penetrates poorly into lung tissue
✅ Answer: C — Daptomycin is inactivated by pulmonary surfactant
Daptomycin is inactivated by pulmonary surfactant. This is a critical NAPLEX fact: Daptomycin is CONTRAINDICATED for pneumonia because alveolar surfactant binds and inactivates it, making it ineffective. For MRSA pneumonia, use Vancomycin or Linezolid. Daptomycin is appropriate for MRSA bacteremia, endocarditis, and SSTI. Option A (eosinophilic pneumonia) is a rare adverse effect of daptomycin but wouldn't present as a new infiltrate after 2 days of therapy in this context.
Question 5
A 28-year-old HIV-positive patient is antiretroviral therapy (ART)-naive. His CD4 count is 350 cells/μL and viral load is 45,000 copies/mL. According to DHHS guidelines, what is the preferred initial ART regimen?
A. Tenofovir DF/emtricitabine + efavirenz (Atripla) B. Bictegravir/tenofovir alafenamide/emtricitabine (Biktarvy) C. Zidovudine/lamivudine + ritonavir-boosted darunavir D. Rilpivirine/tenofovir DF/emtricitabine (Complera)
✅ Answer: B — Bictegravir/tenofovir alafenamide/emtricitabine (Biktarvy)
Biktarvy (bictegravir/TAF/FTC) is DHHS-preferred for ART-naive patients. Current DHHS preferred regimens for treatment-naive adults include INSTI-based regimens: Bictegravir/TAF/FTC (Biktarvy) or Dolutegravir + TAF/FTC or TDF/FTC. Biktarvy is single-tablet, high barrier to resistance, no food requirement, and minimal drug interactions (no CYP3A4 boosting). Efavirenz-based regimens are no longer preferred due to CNS side effects. Rilpivirine requires food and >500 copies/mL viral load limits.
Question 6
A 65-year-old woman presents with dysuria and urinary frequency. Urine culture grows E. coli (>100,000 CFU/mL). She has no allergies and lives in a community with 25% TMP-SMX resistance rates among uropathogens. What is the most appropriate treatment?
A. TMP-SMX DS twice daily for 3 days B. Nitrofurantoin monohydrate/macrocrystals 100 mg twice daily for 5 days C. Ciprofloxacin 250 mg twice daily for 3 days D. Amoxicillin-clavulanate 875/125 mg twice daily for 7 days
✅ Answer: B — Nitrofurantoin monohydrate/macrocrystals 100 mg twice daily for 5 days
Nitrofurantoin is preferred when local TMP-SMX resistance exceeds 20%. IDSA uncomplicated UTI guidelines: TMP-SMX is first-line ONLY if local resistance is <20%. At 25% resistance, nitrofurantoin (5 days) or fosfomycin (single 3g dose) are preferred alternatives. Fluoroquinolones should be reserved for when other options are not appropriate due to collateral damage on gut flora. Amoxicillin-clavulanate is less effective and promotes resistance. Note: Nitrofurantoin is CONTRAINDICATED if CrCl <30 mL/min.
Question 7
Which of the following antibiotics should be AVOIDED in a patient with glucose-6-phosphate dehydrogenase (G6PD) deficiency who requires treatment for an uncomplicated UTI?
A. Fosfomycin B. Nitrofurantoin C. Cephalexin D. TMP-SMX
✅ Answer: B — Nitrofurantoin
Nitrofurantoin is contraindicated in G6PD deficiency. Nitrofurantoin can cause hemolytic anemia in patients with G6PD deficiency — the drug requires reduction of glutathione, which G6PD-deficient patients cannot adequately perform. Other drugs to avoid in G6PD deficiency: primaquine, dapsone, rasburicase, and certain sulfonamides. Fosfomycin is safe and would be a good alternative here (single 3g dose for uncomplicated UTI).
Question 8
A patient is admitted with hospital-acquired pneumonia (HAP) 7 days after surgery. He has not been intubated. He has no risk factors for drug-resistant organisms. What is the most appropriate empiric antibiotic?
A. Piperacillin-tazobactam + vancomycin B. Azithromycin + ceftriaxone C. Piperacillin-tazobactam monotherapy D. Cefepime + linezolid
✅ Answer: C — Piperacillin-tazobactam monotherapy
Piperacillin-tazobactam monotherapy for HAP without MRSA risk factors. IDSA/ATS HAP guidelines: For HAP (not VAP) without MRSA risk factors (prior IV antibiotics, structural lung disease, MRSA colonization), anti-MRSA therapy is NOT required. Appropriate monotherapy options include piperacillin-tazobactam, cefepime, levofloxacin, or imipenem. MRSA coverage (vancomycin or linezolid) is added only when risk factors are present.
Question 9
A 30-year-old patient with HIV has a CD4 count of 80 cells/μL. Which opportunistic infection prophylaxis should be initiated immediately?
A. Fluconazole for cryptococcal meningitis prophylaxis B. TMP-SMX for Pneumocystis jirovecii pneumonia (PCP) prophylaxis C. Azithromycin for Mycobacterium avium complex (MAC) prophylaxis D. Valganciclovir for CMV retinitis prophylaxis
✅ Answer: B — TMP-SMX for Pneumocystis jirovecii pneumonia (PCP) prophylaxis
TMP-SMX for PCP prophylaxis when CD4 <200. OI prophylaxis thresholds: PCP prophylaxis (TMP-SMX DS daily) → CD4 <200. MAC prophylaxis (azithromycin weekly) → CD4 <50. CMV prophylaxis is NOT routinely recommended even at low CD4 counts; monitoring with ART initiation is preferred. Fluconazole routine prophylaxis for cryptococcal disease is not standard in the US. At CD4 80, PCP prophylaxis is the priority.
Question 10
A pharmacist counsels a patient being discharged on a 10-day course of amoxicillin-clavulanate for a bite wound infection. Which counseling point is most important?
A. Take on an empty stomach for maximum absorption B. Take with food to reduce GI upset and diarrhea C. Avoid dairy products while taking this medication D. Double the dose if a dose is missed
✅ Answer: B — Take with food to reduce GI upset and diarrhea
Take amoxicillin-clavulanate with food to reduce GI adverse effects. The clavulanate component commonly causes nausea, diarrhea, and GI upset, which are significantly reduced when taken with food. Unlike some antibiotics, absorption of amoxicillin-clavulanate is not significantly impaired by food — in fact, taking it with the start of a meal is recommended. Dairy restrictions apply to fluoroquinolones and tetracyclines (chelation with divalent cations), not penicillins.
📌 How to use these
Answer each question before reading the rationale, and treat "right but unsure" as wrong. The rationale matters more than the answer — if you cannot explain why the other three options fail, you have not learned the rule yet. Ready for more? Work through the other free quizzes or the pharmacy law cheat sheet.