Decreasing effect of allantoxanamide, a hyperuricemic agent on renal functions in rats.

Both potassium oxonate and allantoxanamide have been reported as useful reagents for inhibiting urate oxidase, with the hyperuricemic effect of allantoxanamide being longer-lasting than that of oxonate in rats. The present study was done to evaluate the utility of allantoxanamide for investigating problems concerning hyperuricemia using rats. A single intraperitoneal administration of 150 mg/kg allantoxanamide elevated the plasma uric acid level progressively during the experiment for 6 hr, resulting in a much higher level than that maintained by means of repeated dosing with 250 mg/kg potassium oxonate, i.p., at 2-hr intervals. Such a severe and long-lasting hyperuricemia caused by allantoxanamide was due to decreased renal function of uric acid excretion according to its nephrotoxicity in addition to the inhibition of urate oxidase like that by oxonate. Thus, we concluded that allantoxanamide might be a useful reagent for investigating the causes of hyperuricemia with renal failure, but was not a practical agent like oxonate in order to evaluate the response to uricosuric agents.