Clinical Pharmacy and Therapeutics Flashcards

A patient with schizophrenia on olanzapine develops metabolic syndrome. What is the pharmacist's recommended intervention?

Answer: Switch to a metabolically neutral antipsychotic (e.g., aripiprazole, ziprasidone), dietary counseling, and metabolic monitoring

Olanzapine (and clozapine) have the highest metabolic syndrome risk among antipsychotics (weight gain, diabetes, dyslipidemia). Switching to metabolically neutral atypical antipsychotics (aripiprazole, ziprasidone, lurasidone) reduces metabolic burden while maintaining antipsychotic coverage. Metformin is a helpful adjunct but not sufficient alone.

Which opioid analgesic is most appropriate for pain management in a patient with renal failure?

Answer: Fentanyl or hydromorphone (with dose reduction) — metabolites less renally toxic than morphine

Morphine is contraindicated in significant renal failure because its active metabolites (morphine-6-glucuronide) accumulate, causing prolonged CNS/respiratory depression. Meperidine is contraindicated (normeperidine accumulation causes seizures). Fentanyl has inactive metabolites and is preferred; hydromorphone can be used with dose reduction.

A patient is on tamoxifen for breast cancer. Which CYP2D6 inhibitor must be avoided because it reduces tamoxifen's activation to endoxifen?

Answer: Paroxetine (SSRI/CYP2D6 inhibitor)

Tamoxifen requires CYP2D6-mediated conversion to endoxifen (the active metabolite responsible for anti-tumor effect). Strong CYP2D6 inhibitors — especially paroxetine and fluoxetine — dramatically reduce endoxifen levels, potentially reducing tamoxifen's effectiveness. Venlafaxine, citalopram, or mirtazapine are preferred alternatives.

A patient with HIV is on tenofovir disoproxil fumarate (TDF). Which renal parameter requires regular monitoring?

Answer: Serum creatinine and estimated GFR, urine protein, and phosphate — TDF causes proximal tubular toxicity

TDF can cause proximal renal tubular toxicity (Fanconi syndrome), presenting with elevated creatinine, proteinuria, hypophosphatemia (phosphate wasting), glucosuria, and decreased GFR. Regular renal function monitoring (creatinine, GFR, urine protein/phosphate) is mandated. TAF (tenofovir alafenamide) has lower renal risk.

A pharmacist identifies that a patient on warfarin has been started on amoxicillin-clavulanate for a dental infection. What is the recommended management?

Answer: Increase INR monitoring frequency (within 3–5 days); adjust warfarin dose if INR changes; educate patient about bleeding signs

Antibiotics can affect warfarin response by altering gut flora (reducing vitamin K production) and potentially inhibiting CYP2C9. The interaction is unpredictable and variable. The recommended approach is increased INR monitoring (within 3–5 days of starting antibiotic), patient education about bleeding, and dose adjustment based on INR result.

A pharmacist is calculating the loading dose for digoxin in a 70 kg patient. The target plasma concentration is 1 ng/mL and the Vd is 7.3 L/kg. What is the loading dose?

Answer: 511 mg (rounded to 500 mcg/0.5 mg)

Loading dose = Target concentration × Vd. Vd = 7.3 L/kg × 70 kg = 511 L. Target Cp = 1 ng/mL = 1 mcg/L. Loading dose = 1 mcg/L × 511 L = 511 mcg ≈ 500 mcg (0.5 mg), divided across 2–3 doses for safety. Note: this calculation demonstrates the principle of loading dose = Cp,target × Vd.