6-Mercaptopurine (6-MP), frequently used in drug regimens for neoplastic disease, is metabolized by xanthine oxidase. Major dose reductions are advised in patients who are being treated with
**Core Concept**
6-Mercaptopurine (6-MP) is a purine analog used in the treatment of various neoplastic diseases, including acute lymphoblastic leukemia. Its metabolism involves the enzyme xanthine oxidase, which is responsible for converting 6-MP into its active metabolites.
**Why the Correct Answer is Right**
The correct answer involves understanding the role of xanthine oxidase in the metabolism of 6-MP. Xanthine oxidase is a key enzyme in the catabolism of purines, and its inhibition can lead to increased levels of 6-MP, potentially causing toxicity. Therefore, patients taking 6-MP require dose adjustments when also taking medications that inhibit xanthine oxidase. Allopurinol, a well-known xanthine oxidase inhibitor, is commonly used in the treatment of gout but can interact with 6-MP.
**Why Each Wrong Option is Incorrect**
**Option A:** Azathioprine is another purine analog used in immunosuppressive therapy, but it is metabolized differently and does not require dose adjustments with xanthine oxidase inhibitors.
**Option B:** Cyclophosphamide is an alkylating agent used in chemotherapy, and its metabolism does not involve xanthine oxidase.
**Option C:** The correct answer is omitted from this explanation.
**Clinical Pearl / High-Yield Fact**
When managing patients on 6-MP, it's essential to consider potential interactions with xanthine oxidase inhibitors, such as allopurinol, to avoid toxicity. A simple mnemonic to remember the interaction is "6-MP + Allopurinol = Increased Risk of Toxicity."
**Correct Answer:** C. Allopurinol.