If Azathioprine or 6-mercaptopurine is given concurrently with Allopurinol, increase the risk of hematological torxicities. Efffect of adenine arabinoside is increased in the presence of Allopurinol. Allopurinol, if given concomitantly with Chlorpropamide the risk of prolonged hypoglycaemic activity increases.

Allopurinol may inhibit metabolism of Phenytoin and Theophylline. An increase in frequency in skin rash has been seen in patients receiving Ampicillin or Amoxicillin concurrently with Allopurinol. Also, the level of Ciclosporin may be increased during concomitant treatment with Allopurinol.

Allopurinol is a drug used in treatment of gout (A painful inflammation of the big toe and foot) and other conditions related with high level of uric acid in the body like kidney disease, cancer and treatment with diuretics. The drug works by inhibiting the enzyme xanthine oxidase that plays a role in converting hypoxanthine to xanthine and uric acid. Allopurinol thus reduces the production of uric acid and alleviates all symptoms associated with high uric acid level.