Folic acid, also known as vitamin B9, is a water-soluble vitamin that plays a role in various bodily functions, including cell growth and DNA synthesis. Methotrexate is a medication frequently used to manage certain autoimmune conditions, such as rheumatoid arthritis and psoriasis, and some types of cancer. These two substances are often prescribed together. This co-prescription aims to achieve therapeutic benefits while managing potential challenges.
How Methotrexate Works
Methotrexate interferes with the body’s use of folate. It functions as an antifolate drug by inhibiting the enzyme dihydrofolate reductase (DHFR). This enzyme converts dihydrofolate into tetrahydrofolate, a form of folate essential for DNA synthesis, cell division, and repair. By blocking DHFR, methotrexate depletes active folate within cells.
This mechanism is useful in conditions characterized by rapid cell proliferation. In autoimmune diseases, methotrexate reduces inflammation and slows the overactive immune response by inhibiting the growth of certain immune cells. For cancer treatment, its ability to disrupt DNA synthesis slows the growth of rapidly dividing cancer cells. While this antifolate action treats these conditions, it also impacts healthy cells that rely on folate, leading to potential side effects.
Why Folic Acid is Prescribed
The interference with folate metabolism caused by methotrexate can lead to a functional folate deficiency. This deficiency affects rapidly dividing healthy cells, such as those lining the gastrointestinal tract, hair follicles, and bone marrow. Consequently, patients taking methotrexate may experience common side effects like nausea, oral ulcers, fatigue, and hair thinning. More severe effects can include liver enzyme elevations and bone marrow suppression.
Folic acid supplementation mitigates these adverse effects without compromising methotrexate’s therapeutic action. By providing an external source of folate, folic acid replenishes folate levels in healthy cells, allowing them to carry out their normal functions. This targeted supplementation alleviates or prevents many of the uncomfortable and potentially serious side effects associated with methotrexate treatment. The timing and dosage of folic acid are carefully managed to ensure it provides protective benefits to healthy cells while still allowing methotrexate to exert its desired effect on diseased cells.
Essential Supplementation Guidelines
When taking folic acid with methotrexate, adhering to the healthcare provider’s specific instructions is important. The dosage and schedule for folic acid supplementation can vary significantly depending on the methotrexate dose, the specific condition being treated, and individual patient tolerance. Some patients may be advised to take folic acid daily, while others might take it once a week, often on a day different from their methotrexate dose to maximize its protective effect without interfering with the primary drug’s action.
Patients should never adjust their folic acid dosage or schedule without consultation with their healthcare provider. Self-adjusting medication can potentially reduce the effectiveness of methotrexate or fail to prevent side effects. Regular monitoring by a doctor, which may include blood tests to check liver function and blood cell counts, is standard practice when patients are on methotrexate and folic acid therapy. This oversight ensures the treatment remains safe and effective while minimizing potential complications.