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Methotrexate: side effects, uses, and dose

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Methotrexate: side effects, uses, and dose

Methotrexate is used for cancer at high doses; and at low doses for rheumatic, inflammatory, and auto-immune diseases. While Methotrexate has improved the quality of life for various diseases like rheumatoid arthritis and Psoriasis, it should be taken under the strict supervision of a doctor. We recommend reading this article before you start this medicine. 

Methotrexate mechanism of action

Methotrexate works by inhibiting the enzyme dihydrofolate reductase when used at higher doses in cancer patients. This enzyme converts folic acid to its active form, called tetrahydrofolate. The latter is necessary for making DNA and RNA. 

Without DNA and RNA, cancer cells cannot multiply further. However, Methotrexate might affect fast-multiplying cells, like blood cells.

At low doses, Methotrexate inhibits the enzyme AICAR transformylase. This leads suppression of primary defense cells, T cells, and B cells. Therefore, low-dose Methotrexate is used for diseases where immune cells are overactive. 

What is Methotrexate dose?

Methotrexate is usually given once a week orally or as an injection. The dose might vary from 2.5 mg to 30 mg, as decided by the doctor. It is better to consult a doctor from ArabiaMD, and get a full body check-up before you start taking Methotrexate.

How bad is Methotrexate for you?

No doubt, Methotrexate is bad for the body. However, the doctor prescribes Methotrexate when the disease is worse than Methotrexate.

Moreover, robust monitoring guidelines have considerably reduced the chance of getting side effects.

What are methotrexate side effects?

At low doses, Methotrexate causes the following side effects

Common side and less severe effects 

  • Nausea and vomiting
  • Mouth ulcers
  • Loss of appetite

Severe and rare side effects

  • Increase in liver enzyme
  • Decrease in Platelet count
  • Decrease hemoglobin
  • Decrease leucocyte count

At high doses used in cancer patients, side effects of Methotrexate are severe, for example:

  • Hair loss
  • Increased risk of infection
  • Bleeding
  • Pancreatitis
  • Bone marrow suppression
  • Cancer
  • Kidney damage

What precautions should you take while on Methotrexate?

Before starting Methotrexate, discuss all health concerns with the doctor. Methotrexate is avoided in case of severe problems in the liver, kidney, bone marrow etc. 

Secondly, Methotrexate levels get altered with many medications, so disclosing a complete list of medications is essential. For example, painkillers and acidity medicines can interact with Methotrexate. 

Do not miss any follow-up visit with a doctor because the dose of Methotrexate is altered based on the response, and you would have to undergo a blood test to monitor side effects.

Call the doctor in case of unusual symptoms, like fever, giddiness, lethargy, bleeding, etc. 

Methotrexate is prescribed intermittently to reduce the activity of the disease. It is essential to take note of the cumulative dose taken in a lifetime. The chance of liver damage increases after 1.5 g of the total dose of Methotrexate. 

Lastly, use two methods of contraception while on Methotrexate. It is not advisable to plan a baby if either parent is on Methotrexate. 

Can you have a healthy baby on Methotrexate?

A baby’s chances of getting developmental abnormalities are high while either parent is taking Methotrexate. Therefore, avoid pregnancy if either of the parents is on Methotrexate.

In the case of females, Methotrexate lowers the level of folic acid, which is essential for the development of the fetus. While in Males, Methotrexate might lead to mutation in sperm cells. 

How long should you wait before planning a pregnancy?

The washout period suggested is variable in studies. Few studies recommend one month in the case of females and three months in males. In contrast, others recommend waiting for 6-12 months, especially after stopping the high dose of Methotrexate. 

The best solution is to follow the doctor’s advice because they know the effect of the dose and duration of Methotrexate in your scenario. 

How effective is Methotrexate for Psoriasis?

FDA approved Methotrexate for use in Psoriasis in the year 1972. methotrexate works by reducing the proliferation of skin cells and suppressing the activity of T cells. 

Methotrexate is started at a low dose, and the dose is increased gradually based on response. Most patients of psoriasis start showing clearance in 4 weeks. however, Methotrexate is continued till full clearance is achieved. 

The doctor might initially request consultation twice a month and then once a month until all the patches of Psoriasis clear. At each visit, a check-up is done to see the response and development of side effects. You might have to take blood tests to rule out side effects.

How Methotrexate monitoring is done?

Before starting Methotrexate following tests are done:

-Complete blood count, including platelet count

-Liver function test

-Kidney function test

-Chest X-ray

-Pregnancy test

While on Methotrexate following tests are done weekly for the first four weeks and then at least bimonthly. 


-Serum creatinine


Takeaway Message

Methotrexate has side effects, however, when used under the supervision of a doctor, it can improve the quality of life for patients with various diseases. Make sure you follow the doctor’s instructions and do not miss any follow-up visits to avoid methotrexate side effects.



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