What it does / How it works
Methotrexate is a disease modifying antirheumatic drug (DMARD) used to treat active psoriatic arthritis. It works by suppressing the immune system—stopping the body from attacking itself. This helps to slow the progression of the disease and save your joints and tissue from permanent damage.
Most people start to see treatment benefits about 6-8 weeks after starting methotrexate. Dose changes can take about a month to take effect. In some, methotrexate can be very effective as a long-term strategy to prevent flares.
Methotrexate comes in an oral tablet formulation and as a vial for injection into the muscle or under the skin.
Dose and frequency
The dose required to achieve clinical efficacy varies between individuals. The recommended starting dose of methotrexate is between 5 and 10mg per week for the first one or two weeks followed by dose increases to a target of 25 mg per week. Take methotrexate as directed by your doctor for optimal dosing.
Potential Side Effects
Potential side effects include nausea, anorexia, mouth ulcers and tiredness. More serious side effects include liver, kidney, lung, and bone marrow problems. Methotrexate can also cause fetal death or birth defects involving the limbs and brain. Patients should ensure they are not pregnant before starting methotrexate and should consider methods of contraception while taking methotrexate. Patients looking to get pregnant after stopping methotrexate should consult their physician before doing so.
Although effective in many patients, methotrexate may increase your risk of infection because it suppresses the immune system. Vaccines can help to reduce your risk of certain infections. Talk to your doctor or pharmacist for more information.
How to manage side effects
Taking this medication with food can help to minimize side effects such as upset stomach, nausea, and diarrhea. Taking folic acid can also help. Folic acid is usually given daily except on the day methotrexate is taken. Taking folic acid or folinic acid (usually, once a week) can help to reduce side effects such as upset stomach, nausea, and diarrhea. Folic acid and folinic acid are considered equally efficacious but folic acid is usually less expensive. Talk to your doctor about whether you should consider taking folic acid or folinic acid as part of your treatment plan.
Some prescription and over the counter medications may interact with methotrexate and increase the risk of adverse reactions. It’s important to share what other medications and supplements you are taking with your doctor. Your doctor or pharmacist can help you manage or prevent these interactions.
Monitoring and follow up
Prior to treatment, clinical and laboratory evaluation should be done to check for pre-existing hepatitis virus B and hepatitis virus C infection. Methotrexate is not recommended for patients with active or chronic hepatitis B or C infection.
Liver damage and function tests should be performed several times prior to dosing and periodic blood tests should be done to check for liver problems and other side effects. Alcohol use must be limited.
Methotrexate is eligible for coverage under your provincial drug plan. Talk to your pharmacist for details. [LINK: See public insurance for more details.]