Renal dosing and funding query for apixaban
A GP phones your community pharmacy about a 79-year-old Māori woman with non-valvular atrial fibrillation. She weighs 52 kg and has a serum creatinine of 150 µmol/L (eGFR 26 mL/min/1.73 m²). The GP wants to start apixaban but is unsure about the dose and whether it is funded without a Special Authority. The patient is also taking clarithromycin for a chest infection. The GP has a printout from an overseas app recommending apixaban 5 mg twice daily. You have access to the NZ Formulary, Medsafe datasheets, the Pharmaceutical Schedule, and local HealthPathways. The pharmacy is busy and the GP wants an answer in 10 minutes. The patient has previously had a fall at home and lives alone. The GP asks you to 'just confirm the app dose' so the prescription can be sent electronically.
1. How would you evaluate the apixaban dose and the clarithromycin interaction, and what would you recommend?
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I would not simply confirm the app dose. The NZ Formulary and Medsafe datasheet are the appropriate NZ references, with the Pharmaceutical Schedule for funding. For apixaban in non-valvular AF, dose reduction to 2.5 mg twice daily is generally indicated when at least two of the following apply: age ≥80 years, weight ≤60 kg, serum creatinine ≥133 µmol/L. This patient meets two criteria (weight 52 kg and creatinine 150 µmol/L), so the standard 5 mg twice daily dose is likely too high. However, clarithromycin is a strong CYP3A4 and P-glycoprotein inhibitor and may increase apixaban exposure; the datasheet/NZF should be checked for specific advice. Because the patient is frail, lives alone, and has had a fall, bleeding risk is high. I would recommend discussing an alternative antibiotic or an alternative anticoagulant with the GP, and not sending the prescription until the interaction and dose are resolved. If apixaban is still appropriate, the reduced dose and interaction plan should be documented.
2. What is the funding position, and how would you confirm it?
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Funding is not the same as clinical appropriateness. I would check the Pharmaceutical Schedule for apixaban's funded status and any Special Authority criteria for non-valvular AF. If a Special Authority is required, the GP must complete it with the relevant clinical data (e.g. eGFR, weight, age, stroke risk). I would not tell the GP it is 'funded without a Special Authority' unless the Schedule confirms that. If the patient does not meet the criteria, I would explain the out-of-pocket cost or alternatives. I would document the Schedule version/date checked, because funding rules change. I would also check whether the patient has a high use health card or other subsidy, but that does not replace the Special Authority process. The 10-minute pressure should not lead to an unverified funding statement.
3. What resources would you use, in what order, and how would you document your advice?
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For clinical dosing and interactions: NZ Formulary first, then Medsafe datasheet for product-specific detail, then local HealthPathways for pathway context. For funding: Pharmaceutical Schedule, including Special Authority. I would not use the overseas app as the primary source because its regulatory and funding context differs. I would document the patient details, the question, the references checked with dates, the recommendation including uncertainty, the GP's response, and the follow-up plan. If the GP insists on the app dose, I would clearly record my advice and escalate to the prescriber's supervisor if needed. Documentation should be contemporaneous and factual.