Allopurinol Low Start CKD Rationale — SCE Rheumatology MCQ

Correct answer: A — In CKD the renal clearance of Allopurinol and its active metabolite oxypurinol is reduced increasing the risk of dose-dependent toxicity (particularly Allopurinol hypersensitivity syndrome); starting at 50 mg with slow uptitration allows safe dose finding

Oxypurinol (the active metabolite of Allopurinol) is predominantly renally cleared. In CKD reduced clearance leads to higher oxypurinol levels increasing the risk of dose-dependent adverse effects including the rare but potentially fatal Allopurinol hypersensitivity syndrome (DRESS). BSR 2017 and NICE 2022 guidelines recommend starting at a lower dose in CKD (50 mg daily in CKD stage 3-5 or even 50 mg on alternate days in severe CKD) with gradual uptitration guided by serum urate response. Importantly the treat-to-target principle still applies: the dose should be increased until the serum urate target is achieved provided there is no toxicity. Evidence from Stamp et al 2017 showed this approach is safe.

Reference: BSR 2017 gout; Stamp LK et al 2017 Allopurinol dose escalation in CKD