Cancer Chemo and Allopurinol

A patient who is going to have chemotherapy and there is going to be a high cell turnover rate like in leukemia and lymphoma Allopurinol should be given as a prophylaxis for uric acid stones.

Allopurinol = prodrug converted by xanthine oxidase, forming alloxanthine which inhibits xanthine oxidase (suicide substrate). 

Inhibiting xanthine oxidase = decreases purine metabolism, which decreases uric acid which decreases uric acid stones. 

Allopurinol is used in gout.

It also inhibits the metabolism of 6-mercaptopurine raising its toxicity. 

Side effects = GI, peripheral neuropathy, rash, vasculitis and stone formation.