Purinethol (mercaptopurine) has significant interactions with which drug?

Purinethol, or mercaptopurine, is an antimetabolite used primarily in the treatment of certain types of cancer and autoimmune diseases. When it comes to significant drug interactions, allopurinol is known to interact with mercaptopurine in a clinically relevant way.

Allopurinol is a xanthine oxidase inhibitor that reduces uric acid levels by inhibiting the conversion of hypoxanthine and xanthine to uric acid. In patients taking mercaptopurine, the presence of allopurinol can lead to increased levels of mercaptopurine in the body. This occurs because allopurinol decreases the metabolism of mercaptopurine, leading to a greater effect and potential toxicity from mercaptopurine. As a result, dosages of mercaptopurine often need to be reduced in patients receiving allopurinol to avoid adverse effects.

Understanding this interaction is crucial, as excessive mercaptopurine levels could lead to side effects such as bone marrow suppression, which can have serious or even life-threatening implications. The need for careful monitoring and dosage adjustments highlights the significance of the interaction between these two medications.