Methotrexate, which used to be called methotrexate, is often abbreviated as MTX according to its English name. careful patients who read the drug’s instructions will find that methotrexate is primarily used to treat leukemia and certain tumors. In fact, methotrexate is also widely used for rheumatoid arthritis, intractable psoriasis, psoriatic arthritis, dermatomyositis and other immune diseases. Methotrexate has been recognized internationally by rheumatologists as the most important drug for the treatment of rheumatoid arthritis.
Methotrexate is a folic acid antagonist, which mainly inhibits the enzyme dihydrofolate reductase and prevents the reduction of dihydrofolate to physiologically active tetrahydrofolate, thus blocking the biosynthesis of purine and pyrimidine nucleotides, the raw materials required for DNA synthesis, and thus inhibiting cell division and proliferation. In short, methotrexate has the opposite effect of folic acid in the body in that it inhibits the growth and multiplication of tumor cells and immune inflammatory cells. This is the basis for its ability to treat both tumors and immune disorders.
Methotrexate rarely causes serious side effects if used only in small doses each week. Its common side effects include, mouth ulcers or stomatitis, stomach upset, nausea, loss of appetite, and elevated liver transaminases (liver function impairment). Occasionally, bone marrow suppression (blood leukopenia and thrombocytopenia), hair loss, and pulmonary fibrosis occur. Methotrexate also decreases sperm count in men, but this is restored when the drug is discontinued. Methotrexate does not affect fertility, but methotrexate use in women who are pregnant may result in neonatal defects. To avoid adverse reactions as much as possible, patients taking methotrexate should pay attention to the following: 1. Exclude unsuitable people. Before starting methotrexate treatment, laboratory tests should be performed for routine blood tests, liver and kidney functions, hepatitis B-5, hepatitis C antibodies, HIV antibodies, and pregnancy tests. It is not suitable for those with liver and kidney insufficiency, chronic infection and pregnant women.
2.Supplement folic acid in appropriate amount. Taking 1 tablet (5mg) of folic acid on the 2nd or 3rd day of weekly methotrexate (≥15mg) can significantly reduce methotrexate-induced oral ulcers, elevated liver transaminases, gastrointestinal discomfort and other adverse reactions, and does not reduce the efficacy of methotrexate. However, the opposite is true for everything. If taking folic acid daily will reduce the absorption of methotrexate and lower its blood concentration, the efficacy will be reduced. I often find patients who take 1-2 tablets (2.5-5mg) of folic acid every day, which reduces the efficacy of methotrexate and keeps the disease from being effectively controlled. If methotrexate (≤10mg) is taken weekly, routine supplementation of folic acid is not recommended.
3. Change from oral to intramuscular injection. If the patient has severe nausea or even vomiting after taking methotrexate tablets, he can switch to methotrexate injection and inject it intramuscularly once a week (5-15mg).
4. Prohibit drinking alcohol. Because alcohol increases the risk of methotrexate induced liver damage.
5. Combination of medications according to medical advice. For example, sulfonamides may cause an increase in the serum concentration of methotrexate and lead to toxic reactions. Aminoglutethimide and pyrimethamine have anti-folate effects, and their toxic effects may be increased if used together with methotrexate. Therefore, if you need to take other drugs during the medication, you should consult your doctor to avoid adverse reactions.
6. Proper contraception. Because it may lead to fetal malformation, you need to stop taking the drug for more than three months before you can get pregnant.
7. Prohibit breastfeeding. Do not take methotrexate during breastfeeding, because it will enter the baby’s body through breast milk.
8. Regular laboratory tests. Have your blood tests, liver function and kidney function checked at least every month for the first 3 months after you start taking methotrexate. When taking methotrexate for a long period of time, review the blood routine, liver function and kidney function at least once every three months.
Because rheumatoid arthritis is an intractable disease, for most patients, it is difficult to control the disease with one drug alone. Clinically, methotrexate is often used in combination with 2-4 drugs (including anti-inflammatory and painkillers, even including prednisone). For patients with rheumatoid arthritis, methotrexate is indeed a good drug. Although it has many adverse effects, its benefits far outweigh the disadvantages as long as it is used regularly. Based on our experience, methotrexate is safe and effective for the majority of patients. In addition, it has the advantage that it can be taken orally and is quite inexpensive.
The first oral dose of methotrexate is often 5-10 mg (2.5 mg per tablet) once a week (please note that it is not a daily dose). Depending on efficacy and tolerability, the dose may be increased by 2.5mg every 2-4 weeks to a maximum dose of 15-25mg once a week.