noun. A substance that closely resembles an essential metabolite and therefore interferes with physiological reactions involving it.

noun. Any substance that competes with, or inhibits the normal metabolic process, often by acting as an analogue of an essential metabolite

noun. an antineoplastic drug that inhibits the utilization of a metabolite

"When this process is allowed to proceed normally it is also called “metobolizing,” somethotrexate is also called an “antimetabolite.”"

antineoplastic  antineoplastic drug  cancer drug  

amethopterin  fluorouracil  mercaptopurine  methotrexate  methotrexate sodium