Q: Is there any benefit to receiving methotrexate by injection as opposed to taking it orally? Is it metabolized differently? Are the side effects of methotrexate injection different?

A: Methotrexate is a disease-modifying antirheumatic drug (DMARD) used to slow the disease process and treat the pain and swelling of rheumatoid arthritis. The body's absorption of the drug, and therefore its effectiveness, varies among individual patients when the drug is taken orally. To improve methotrexate's effectiveness, physicians may increase the oral dosages or try intramuscular methotrexate injection. 

Although the injections may help improve the medication's effectiveness, the potential side effects and benefits of methotrexate are virtually the same whether it is given orally or by injection. Liver damage remains the main concern, and is monitored by frequent blood tests. Taking 1 mg of folic acid per day can help reduce other side effects related to methotrexate use, such as mouth sores or gastrointestinal irritation.

David Pisetsky, MD, PhD, Rheumatologist