In patients receiving mercaptopurine (Purinethol) or azathioprine (Imuran), the concomitant administration of 300-600 mg of allopurinol per day will require a reduction in dose to approximately one-third to one-fourth of the usual dose of mercaptopurine or azathioprine.
<allopurinol, advise, mercaptopurine>, <allopurinol, advise, azathioprine>