What is a significant side effect of methotrexate?

Methotrexate is an antimetabolite and antifolate medication widely used in cancer therapy and autoimmune diseases. One significant side effect associated with its use is transaminase elevations. This occurs because methotrexate can affect liver function, leading to an increase in the levels of liver enzymes, specifically alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Regular monitoring of liver function tests is essential for patients on methotrexate to identify any hepatic toxicity early on.

While diarrhea, neurotoxicity, and anaphylaxis are also important considerations in patients receiving methotrexate, they are not as commonly associated with its use as transaminase elevations. Diarrhea can occur but is more directly linked with other chemotherapy agents or related treatments. Neurotoxicity is generally associated with higher doses of methotrexate or specific administrations, such as intrathecal therapy, and anaphylaxis, though a serious allergic reaction, is rare. Thus, transaminase elevations are the more prevalent and clinically significant side effect that requires careful monitoring and management during methotrexate treatment.