Nephrotoxic effects of allopurinol in dinitrofluorobenzene-sensitized mice: comparative studies on TEI-6720

Allopurinol is widely used and generally well-tolerated. However, when used in patients with renal insufficiency it may have life-threatening toxic effects known as allopurinol hypersensitivity syndrome (AHS). We previously found that allopurinol increased ear swelling and mortality in a DNFB-induced contact hypersensitivity mouse model. In the present study, we investigated the toxic effect of allopurinol on DNFB-sensitized mice in order to clarify the mechanism responsible for the lethal effect of allopurinol. Allopurinol increased plasma GPT and GOT in DNFB-sensitized mice and markedly increased plasma creatinine and BUN. The increase in plasma GPT and GOT was moderate and declined time-dependently. In contrast, the increase in plasma creatinine and BUN was striking and continued until 18 hr after administration of allopurinol at 100 mg/kg/day. Although allopurinol increased GOT and GPT in DNFB-sensitized mice, no effect was observed in non-sensitized mice even at 100 mg/kg/day, indicating that allopurinol essentially has no toxic effect on the liver. A high dose of allopurinol induced renal impairment even in non-sensitized mice. These observations indicate that there is some biological interaction between allopurinol and DNFB, and suggest that allopurinol may modulate or enhance the inflammatory reactions induced by DNFB, and/or that DNFB may cause metabolic changes via inflammation, leading to the enhanced toxicity of allopurinol. In contrast, TEI-6720, a newly synthesized XOD/XDH inhibitor, had almost no effect on DNFB-sensitized mice. TEI-6720 at 1 mg/kg, in terms of hypouricemic effect, appeared to be more potent than allopurinol at 3 mg/kg. Therefore, the nephrotoxic effect of allopurinol observed in the present study may not be related to XOD/XDH inhibitory activity.