Physician Assistant Pharmaceutical Therapeutics 2 — Questions and Answers
Question 1: A patient with CKD stage 3 is started on metformin. Which creatinine clearance threshold requires discontinuation of metformin?
- < 60 mL/min
- < 45 mL/min
- < 30 mL/min (Correct answer)
- < 15 mL/min
Correct answer: < 30 mL/min
Metformin is contraindicated when eGFR falls below 30 mL/min/1.73m² due to risk of lactic acidosis.
Question 2: Which antibiotic class is most appropriate for empiric treatment of community-acquired pneumonia in an otherwise healthy outpatient with no recent antibiotic use?
- Fluoroquinolone
- Macrolide monotherapy (Correct answer)
- Beta-lactam + macrolide
- Carbapenems
Correct answer: Macrolide monotherapy
IDSA/ATS guidelines recommend macrolide monotherapy (e.g., azithromycin) for healthy outpatients with no comorbidities.
Question 3: A 65-year-old on warfarin for atrial fibrillation starts clarithromycin. What adjustment is needed?
- Increase warfarin dose by 25%
- No adjustment needed
- Reduce warfarin dose and monitor INR closely (Correct answer)
- Switch to aspirin
Correct answer: Reduce warfarin dose and monitor INR closely
Clarithromycin inhibits CYP3A4 and CYP2C9, reducing warfarin metabolism and increasing INR; dose reduction and close monitoring are required.
Question 4: Which NSAID is preferred in a patient who requires analgesia and has a history of peptic ulcer disease with H. pylori eradication completed?
- Indomethacin
- Ketorolac IV
- Celecoxib with a PPI (Correct answer)
- High-dose aspirin
Correct answer: Celecoxib with a PPI
A COX-2 selective inhibitor combined with a PPI provides analgesia with the lowest GI risk in patients with prior ulcer disease.
Question 5: A patient taking lisinopril develops a dry, nonproductive cough. What is the most appropriate alternative antihypertensive?
- Enalapril
- Losartan (Correct answer)
- Hydrochlorothiazide
- Amlodipine
Correct answer: Losartan
ARBs (e.g., losartan) do not cause bradykinin accumulation and are the preferred substitute for ACE inhibitor-induced cough.
Question 6: Which pharmacokinetic parameter best describes how a drug distributes throughout the body and is used to estimate loading dose?
- Half-life
- Clearance
- Volume of distribution (Correct answer)
- Bioavailability
Correct answer: Volume of distribution
Volume of distribution (Vd) reflects drug distribution into tissues and is used in the formula: Loading dose = Cp × Vd / bioavailability.
Question 7: A patient on lithium begins taking ibuprofen for arthritis. Which effect is most likely?
- Decreased lithium levels
- Increased lithium levels and toxicity risk (Correct answer)
- No significant interaction
- Decreased ibuprofen efficacy
Correct answer: Increased lithium levels and toxicity risk
NSAIDs reduce prostaglandin-mediated renal lithium excretion, causing lithium accumulation and potential toxicity.
Physician Assistant Pharmaceutical Therapeutics 2
A patient with CKD stage 3 is started on metformin.
Which creatinine clearance threshold requires discontinuation of metformin?