Methotrexate
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For arthritis, methotrexate is taken ONCE A WEEK, on the same day each week. It is never taken every day, taking it daily by mistake can be very dangerous. It comes as tablets or as a small injection under the skin. Food, especially milk, can lower how much of the tablet your body absorbs, so many people take it with a little water away from meals. Your team will also prescribe folic acid to take on a different day of the week, which lowers side effects.
- Rheumatoid arthritis: Usually started at a low weekly dose and slowly increased, up to about 25 mg once a week, until it works. At higher doses the injection under the skin is often used because the body absorbs it better than tablets.
- Psoriatic arthritis and psoriasis: Often uses a somewhat higher weekly dose than for rheumatoid arthritis, adjusted to response.
It usually starts to help within about 3 to 6 weeks, and the full effect can take 12 weeks or longer.
Tests while you take it
Before you start, you will have blood tests and a chest X-ray. Blood tests that check your blood counts, liver, and kidneys are then repeated about once a month, and more often when your dose is changing.
What to know
Common side effects
The most common effects are feeling sick, a sore mouth, or tiredness, often on the day after your dose. Taking folic acid, and sometimes switching to the injection, helps. Less often it can affect the blood counts or the liver, which is why regular blood tests matter.
Tests and monitoring
You will have blood tests to check your blood counts, liver, and kidneys. They are done before you start, more often in the first few months and after any dose increase (about every 2 to 4 weeks), then usually about every 3 months once your dose is steady. If you have risk factors, your team may also test for hepatitis B and C before you start.
Alcohol
Alcohol and methotrexate are both handled by the liver, which is one of the reasons for the regular blood tests. Advice on drinking varies between rheumatologists, so the number that counts is the one your own team gives you. Dr. Mahendira suggests no more than one standard drink a week while you are taking methotrexate. That is a cautious position and it is her recommendation, not a national rule. For wider context, Canada's national guidance is not specific to methotrexate. It describes a continuum rather than a limit: two standard drinks or fewer a week is the level at which most alcohol-related harm is avoided, three to six a week raises the risk of several cancers, and seven or more raises the risk of heart disease and stroke. It also advises no more than two on any single day. A standard drink in Canada is 341 mL of 5% beer or cider, 142 mL of 12% wine, or 43 mL of 40% spirits. Pours at home are often larger than one standard drink. If you are pregnant, trying to conceive, or breastfeeding, no amount of alcohol is known to be safe. Methotrexate is stopped before pregnancy in any case. Tell your team honestly what you drink. It changes how closely they watch your blood tests, not whether they will look after you.
Important cautions
Methotrexate is stopped before pregnancy and is not used during pregnancy, for both women and men planning a baby, so reliable contraception is important. Tell your team before any live vaccine or planned surgery, and let them know promptly if you get an infection.
What to watch for
- Signs of infection with a fever while on methotrexate. Contact your team promptly.
- A new dry cough or breathlessness, which is rare but should be checked without delay.
- Mouth ulcers, unusual bruising or bleeding, or yellowing of the skin or eyes.
- You realise you have taken methotrexate more than once in a week. Contact your team or a pharmacist straight away.