Urinary excretion of purines, pyrimidines and pyrazolopyrimidines in patients treated with allopurinol or oxipurinol

Abstract

When allopurinol was administered to three patients with good renal function, two suffering from gout and one a xanthinuric, the metabolites recovered in the urine (76% of the dose) consisted of oxipurinol (73.6%), allopurinol (10.4%), allopurinol riboside (12.5%) and oxipurinol riboside (3.5%). Only 36% of an equivalent dose of oxipurinol was recovered daily from the urine of the same patients, chiefly in the form of unchanged oxipurinol (94.6%), the remainder being oxipurinol riboside. In the two gouty patients the urinary excretion of xanthine and hypoxanthine was increased during drug treatment and the ratio of xanthine to hypoxanthine excreted was markedly altered. Prior to treatment these two patients had a xanthine/hypoxanthine ratio of 0.68 which increased to 4.15 on allopurinol and 1.75 on oxipurinol. The xanthine/hypoxanthine ratio in the patient with xanthinuria was approximately 5 and not markedly altered throughout the study. In all three patients the pattern of excretion of other urinary purines was not altered by treatment with allopurinol or oxipurinol. A dietary origin is suggested for 1-methylxanthine, 7-methylxanthine and 5-acetylamino-6-amino-3-methyluracil since these compounds were not excreted when purine intake was restricted. The excretion of pseudouridine was excessive in two patients, irrespective of diet. A remarkable finding in these two patients was the replacement of urinary pseudouridine by an equivalent amount of uracil during separate periods of several consecutive days.