Mtx toxicity high dose

High doses of MTX undergo hydroxylation at the 7 position and become 7 hyroxymethotrexate. This derivative is much less active as an antimetabolite. It is less water soluble than MTX and may lead to crystalluria. Therefore, it is important to keep the urine alkaline and the patient well hydrated to avoid renal toxicity. Excretion of the parent drug and the 7-OH metabolite occurs primarily via urine, although some of the drug and its metabolite appear in feces due to enterohepatic excretion.