[Methods of isolation and determination of urinary 4-thio-6-hydroxypyrazolo(3,4 d)pyrimidine in patients treated with thiopurinol].

Oxithiopurinol, [4-thio-6-hydroxypyrazolo(3,4-d)pyrimidine] has been caracterized in urines of patients treated with Thiopurinol : the principle involved is the precipitation of both oxithiopurinol and uric acid in combination with cupric hydroxide. The urinary oxithopurinol content is determined by means of anion and cation exchange resins. 56 to 70 per cent of the daily dose of Thiopurinol are eliminated in urine as oxithiopurinol.