Side effects of Methotrexate

Side effects of methotrexate vary from mild to severe. Methotrexate is a cytotoxic drug. Methotrexate belongs to antimetabolites class of cytotoxic drug. Methotrexate inhibits an enzyme which involves in the DNA synthesis pathway. The enzyme is dihydrofolate reductase. Methotrexate is used to treat variety of diseases such as leukemia, lymphoma and rheumatoid arthritis. Methotrexate is given orally, intravenously, intramuscularly or intrathecally.

Side effects of methotrexate could be due to its inhibitory effect on the enzyme mentioned above. Mere presence of methotrexate can also cause several side effects because it is a cytotoxic drug. Some of the side effects of methotrexate are common to all the cytotoxic drugs whereas some are essentially the side effects of methotrexate. Following are some common side effects of methotrexate;

1. Oral mucositis; a sore mouth is a common side effect of methotrexate. Good mouth care (rinsing the mouth frequently and effective brushing of the teeth with a soft brush 2-3 time daily) is probably effective.
2. nausea and vomiting
3. Bone marrow suppression; this is a common side effect of methotrexate. It occurs 7-10 days after the commencement of methotrexate. Full blood count should be performed regularly and dose of the drug should be changed according to the results of the full blood count.
4. pneumonitis
5. Anemia and neutropenia due to bone marrow suppression
6. Malaise, undue fatigue, chills and fever, dizziness and lowered resistance to infection

Prevention of side effects of methotrexate

1. Lowest effective dose of the methotrexate should be used.
2. Folic acid supplements should be given following methotrexate treatment. This will help to prevent mucositis and bone marrow suppression.
3. Regular blood count check should be done and dose should be changed accordingly.
4. Avoid methotrexate treatment if kidney function is impaired.
5. consider contraindication for methotrexate commencement (impairment of kidney function, severe liver impairment, pleural effusion, ascities)
6. avoid if pregnant