Delayed excretion of conjugated sulphamethoxazole in uraemia

Persistence in the serum of free and conjugated sulphamethoxazole was estimated in five normal controls and in nine uraemic patients with creatinine clearances under 20 ml/min, after a single one-gram dose of the drug. In the uraemic group delayed disappearance of the free drug was found. Conjugated sulphamethoxazole retention was 62.44% at 24 hr after the oral load, and 13.7% 19 days later. Risk of accumulation of sulphamethoxazole in uraemia is emphasised. Re-evaluation of the use of this drug in patients with impaired renal function is recommended.