PEBC Treatment Planning 5 — Questions and Answers
Question 1: A patient with HIV is initiated on an antiretroviral regimen containing tenofovir disoproxil fumarate (TDF). Which organ function requires close monitoring?
- Hepatic function (ALT/AST)
- Renal function (serum creatinine, eGFR) and bone density (Correct answer)
- Thyroid function (TSH)
- Pulmonary function (FEV1)
Correct answer: Renal function (serum creatinine, eGFR) and bone density
TDF is associated with nephrotoxicity and decreased bone mineral density; renal function and bone density monitoring are key components of TDF-based regimen follow-up.
Question 2: A 60-year-old man with gout has a serum uric acid of 620 µmol/L and recurrent flares. He is started on allopurinol. What is the most important counselling point about starting allopurinol?
- Allopurinol will immediately stop any active gout flare
- Gout flares may paradoxically increase in the first months of therapy; prophylactic colchicine or NSAID is recommended (Correct answer)
- Allopurinol must be taken with food to prevent hepatotoxicity
- Uric acid levels will normalize within one week of initiation
Correct answer: Gout flares may paradoxically increase in the first months of therapy; prophylactic colchicine or NSAID is recommended
Mobilization flares commonly occur when starting urate-lowering therapy as urate crystals are mobilized; low-dose colchicine or NSAID prophylaxis for 3–6 months is recommended.
Question 3: A pharmacist is assessing a patient's medication adherence. The patient reports taking their antihypertensive medications only 3–4 days per week. What is the MOST appropriate first intervention?
- Switch to a different medication class without further discussion
- Explore barriers to adherence through motivational interviewing before modifying the regimen (Correct answer)
- Add another antihypertensive to compensate for missed doses
- Refer the patient immediately to a specialist
Correct answer: Explore barriers to adherence through motivational interviewing before modifying the regimen
Identifying and addressing patient-specific barriers through motivational interviewing is the foundational first step before making any therapeutic changes.
Question 4: A patient on amiodarone for atrial fibrillation is also taking warfarin. What adjustment to warfarin dosing is typically required?
- Increase warfarin dose by 50% as amiodarone reduces its absorption
- Reduce warfarin dose by approximately 30–50% as amiodarone inhibits its metabolism (Correct answer)
- No dose adjustment needed; the interaction is clinically insignificant
- Switch warfarin to a DOAC to avoid the interaction completely
Correct answer: Reduce warfarin dose by approximately 30–50% as amiodarone inhibits its metabolism
Amiodarone inhibits CYP2C9 (and CYP3A4), significantly reducing warfarin metabolism and increasing INR; warfarin dose reduction of 30–50% is typically required.
Question 5: A 45-year-old patient with moderate persistent asthma continues to have frequent symptoms despite low-dose ICS. What is the recommended step-up therapy per GINA guidelines?
- Add oral corticosteroids as maintenance therapy
- Add a long-acting beta-2 agonist (LABA) to the existing ICS (Correct answer)
- Switch ICS to a higher-potency agent and discontinue SABA
- Add a leukotriene receptor antagonist and stop ICS
Correct answer: Add a long-acting beta-2 agonist (LABA) to the existing ICS
GINA guidelines recommend adding a LABA to ICS (forming an ICS/LABA combination) as the preferred step-up for uncontrolled moderate persistent asthma.
Question 6: A patient receiving vancomycin for MRSA bacteremia requires therapeutic drug monitoring. Which pharmacokinetic/pharmacodynamic target guides vancomycin dosing optimization?
- Peak vancomycin concentration >20 mg/L
- Trough vancomycin concentration only, targeting 15–20 mg/L
- AUC24/MIC ratio of 400–600 mg·h/L (Correct answer)
- Time above MIC >50% of the dosing interval
Correct answer: AUC24/MIC ratio of 400–600 mg·h/L
Current ASHP/IDSA/SIDP guidelines (2020) recommend AUC-guided vancomycin monitoring with a target AUC24/MIC of 400–600 to optimize efficacy and minimize nephrotoxicity.
Question 7: A pharmacist notices that a prescription for clarithromycin has been written for a patient taking simvastatin 40 mg daily. What is the most appropriate action?
- Dispense both medications with no changes required
- Contact the prescriber to withhold simvastatin during clarithromycin therapy to prevent rhabdomyolysis (Correct answer)
- Reduce simvastatin to 20 mg for the duration of clarithromycin therapy
- Switch clarithromycin to azithromycin and continue simvastatin unchanged
Correct answer: Contact the prescriber to withhold simvastatin during clarithromycin therapy to prevent rhabdomyolysis
Clarithromycin is a potent CYP3A4 inhibitor that dramatically increases simvastatin exposure, raising the risk of myopathy and rhabdomyolysis; simvastatin should be suspended during therapy.
PEBC Treatment Planning 5
A patient with HIV is initiated on an antiretroviral regimen containing tenofovir disoproxil fumarate (TDF).
Which organ function requires close monitoring?