Methotrexate is a medication that has been used for the treatment of various medical conditions, including certain types of cancer, rheumatoid arthritis, and psoriasis. In dermatology, methotrexate is commonly used as a systemic agent for the treatment of moderate to severe psoriasis, particularly for patients who have failed other therapies.

Methotrexate works by inhibiting the activity of an enzyme called dihydrofolate reductase, which is important for the synthesis of DNA and cell replication. This leads to a reduction in the proliferation of cells, including immune cells that are involved in the inflammatory process of psoriasis.

Methotrexate is usually taken once a week, and the dose can vary depending on the patient’s weight, medical history, and response to treatment. Regular monitoring of liver and kidney function, as well as blood cell counts, is essential to ensure the medication is well tolerated and effective.

Some common side effects of methotrexate include nausea, fatigue, mouth sores, and hair loss. In rare cases, more severe side effects such as liver toxicity, lung inflammation, and decreased immunity may occur. Thus, regular monitoring of patients is necessary to ensure safe and effective use.

In dermatology, methotrexate can be used as monotherapy or in combination with other medications for the treatment of psoriasis. It can also be effective for other dermatologic conditions such as atopic dermatitis, cutaneous lupus erythematosus, and blistering disorders. However, its use requires careful consideration of the patient’s medical history and potential risks and benefits.

This learning module covers the pharmacology, mechanisms of action, indications, dosing, adverse effects, drug interactions, and monitoring requirements of methotrexate.

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1. Bolognia, J., Cerroni, L., & Schaffer, J. V. (2018). Dermatology. Philadelphia: Elsevier.

2. Wolverton, S. E. (2021). Comprehensive dermatologic drug therapy. Edinburgh: Saunders.