Clinical Pharmacy and Pharmacotherapy
Clinical Pharmacy and Pharmacotherapy tests patient-centred decision-making: confirming indication, assessing contraindications, individualising dose, monitoring efficacy and toxicity, and recognising drug interactions. OMSB-style cases often include renal function, age, weight, pregnancy, and interacting medicines.
Core rules
- Work through indication → safety → dose → monitoring → counselling. Document the problem list and measurable endpoint.
- Adjust renally cleared drugs for CrCl; do not apply a random 'renal dose' without checking the specific product criteria.
- For direct oral anticoagulants in non-valvular atrial fibrillation, dose reduction criteria are drug-specific; apixaban 2.5 mg BID requires at least two of age ≥80 years, weight ≤60 kg, or SCr ≥1.5 mg/dL.
- High-risk drugs need explicit monitoring: warfarin INR, vancomycin AUC, aminoglycoside levels, lithium, digoxin, insulin, and methotrexate.
- Avoid treating asymptomatic bacteriuria except in defined situations such as pregnancy or before urological procedures.
Worked example
A 68-year-old, 80 kg man with atrial fibrillation has SCr 1.4 mg/dL, CrCl about 42 mL/min, and no other dose-reduction criteria. Apixaban standard dose is 5 mg BID, not 2.5 mg BID: he meets only one reduction criterion (SCr ≥1.5 is false at 1.4; age false; weight false). The CrCl of 42 mL/min does not itself mandate apixaban reduction in non-valvular AF; avoid only if CrCl <15 mL/min. Reasoning: apply labelled criteria, not a general CKD rule.
Traps
- Reducing DOAC dose for mild renal impairment when label criteria are not met.
- Missing interacting drugs that affect CYP3A4/P-gp, such as clarithromycin or ketoconazole.
- Monitoring INRs too early after warfarin initiation.
- Treating a positive urine culture without symptoms.
- Failing to reassess a drug after the acute problem resolves.