Allopurinol: alteration in pyrimidine metabolism in man.

In addition to its well-established inhibitory effect on uric acid synthesis, allopurinol appears to alter substantially pyrimidine metabolism, as evidenced by a striking increase in the urinary excretion of orotidine and orotic acid. Allopurinol ribonucleotide and xanthosine 5'-monophosphate are potent inhibitors of human erythrocyte orotidylic decarboxylase and provide a possible mechanism for this effect.