Apparent metabolism of allopurinol by blood--a preliminary report

Allopurinol is converted to a presently unidentified metabolite by whole blood, both in samples prepared in vitro as well as samples from subjects administered the drug. The apparent plasma concentration of allopurinol, as determined by HPLC, is dependent upon the length of time between sample preparation or sample withdrawl and the centrifugation and removal of plasma. Oxypurinol does not undergo the same conversion, nor does it affect the loss of allopurinol.