Pharmacist Flashcards

A patient on warfarin for atrial fibrillation presents with a new prescription for fluconazole 150 mg single dose for vaginal candidiasis. Which is the MOST appropriate pharmacist action?

Answer: Contact the prescriber to recommend switching fluconazole to topical clotrimazole and document the intervention

Fluconazole is a potent CYP2C9 inhibitor, and even a single 150 mg dose can significantly increase warfarin's anticoagulant effect, raising the risk of serious bleeding. The most appropriate action is to contact the prescriber and suggest a safer alternative (topical azole) that avoids systemic drug interaction, rather than simply dispensing with counseling or arbitrarily stopping warfarin.

Under DHA regulations, which of the following is a pharmacist's legal obligation when a patient presents a prescription for a Schedule I controlled substance that appears authentic but was issued by a physician whose DHA license has been suspended?

Answer: Decline to dispense and report the prescriber to the DHA Pharmaceutical Affairs Department

A prescription issued by a physician with a suspended DHA license is not a valid legal prescription under UAE Federal Law No. 4 of 1983 and DHA regulations, regardless of its physical appearance. The pharmacist must decline to dispense and has a professional duty to report the incident to the DHA Pharmaceutical Affairs Department to protect public safety.

A pharmacist is reviewing a pediatric prescription for oral methotrexate 12.5 mg once weekly for juvenile idiopathic arthritis. The prescription was written as 'methotrexate 2.5 mg tablets — take 5 tablets DAILY.' What is the priority action?

Answer: Contact the prescriber immediately to clarify the dosing frequency before dispensing, as daily dosing is life-threatening

Methotrexate for non-oncologic indications is dosed WEEKLY, never daily. Daily dosing causes severe, potentially fatal myelosuppression and mucositis. This is a well-documented 'never event' in pharmacy. The pharmacist must never dispense until the prescriber clarifies and corrects the order — pharmacist-initiated changes to dosing frequency without authorization are also inappropriate here given the severity of risk.

A patient with a CrCl of 28 mL/min is prescribed rivaroxaban 20 mg once daily with the evening meal for non-valvular atrial fibrillation. What is the MOST clinically appropriate pharmacist recommendation?

Answer: Recommend reducing the dose to rivaroxaban 15 mg once daily with the evening meal for this level of renal impairment

For non-valvular atrial fibrillation, rivaroxaban dose adjustment is required when CrCl is 15–49 mL/min: the dose is reduced from 20 mg to 15 mg once daily with the evening meal. A CrCl of 28 mL/min falls in this range. Rivaroxaban is not contraindicated at this CrCl (contraindicated below 15 mL/min for AF), and switching agents is not necessary when a labeled dose adjustment resolves the issue.

A breastfeeding mother at 4 weeks postpartum presents with a prescription for codeine 30 mg every 4–6 hours for post-cesarean pain. Her infant appears excessively drowsy at the follow-up visit. Which pharmacokinetic phenomenon BEST explains this clinical finding?

Answer: The mother is an ultra-rapid CYP2D6 metabolizer, producing excessive morphine that transfers to breast milk

Codeine is a prodrug converted to morphine by CYP2D6. In ultra-rapid CYP2D6 metabolizers (~1–7% of some populations), codeine is converted to morphine at an accelerated rate, producing higher-than-expected morphine plasma concentrations. This excess morphine transfers into breast milk in clinically significant amounts, causing opioid toxicity in the nursing infant — a pattern that has resulted in neonatal deaths. Codeine is now contraindicated in breastfeeding in most guidelines.

A hospital pharmacist reviews an order for vancomycin in a 70 kg patient with a serum creatinine of 2.4 mg/dL (age 55, male). Using the Cockcroft-Gault equation, the estimated CrCl is approximately 35 mL/min. The order reads: 'Vancomycin 1500 mg IV every 8 hours.' AUC-guided dosing target is 400–600 mg·h/L. What is the MOST appropriate initial action?

Answer: Flag the order as significantly overdosed for this renal function; recommend an extended interval such as 1000–1250 mg every 24–36 hours pending PK consult

Vancomycin is renally cleared and dose/interval must both be adjusted in renal impairment. A CrCl of 35 mL/min with 1500 mg every 8 hours (4500 mg/day) is a grossly excessive regimen that would produce dangerous drug accumulation and nephrotoxicity/ototoxicity. Modern AUC/MIC-guided dosing in moderate renal impairment typically uses extended intervals (every 24–36 hours or longer) with individualized doses. Simply halving the dose while maintaining q8h still delivers excess drug. A PK consult and extended-interval dosing are appropriate.