What is Methotrexate?
Methotrexate is a medication that is classed as a DMARD- a disease modifying anti-rheumatic drug. This means it acts on the disease itself to reduce the effects of the immune system.
The immune system causes inflammation that protects the body from infections and injury. In certain diseases however, the immune system is over active and this can target healthy tissues such as joints. This results in pain, swelling and tenderness and eventually permanent damage.
Methotrexate works to suppress the over activity of the immune system and prevent the inflammation from occurring, reducing the long-term risk of permanent joint damage.
What is Methotrexate used for?
Methotrexate is used for a number of different conditions that cause inflammation such as arthritis. The most common conditions it is used for are rheumatoid arthritis, psoriatic arthritis and vasculitis.
How is it taken?
Methotrexate comes in both a tablet and injection. Tablets are the most common form and come in doses of 2.5mg. It is taken once a week and the day after taking your methotrexate you will be prescribed a vitamin called folic acid to take at 5mg.
The usual starting dose of methotrexate is 15mg weekly, however some people can be on smaller or high doses up to a maximum of 25mg weekly.
If you are struggling with side effects from the tablet, the weekly injection can be used instead. The injection is given into the thigh in the layer of fat between the skin and muscle. You will receive training on how to do this.
It can take up to 12 weeks for the medication to have its full effect. It is a long-term treatment as it prevents any long-term damage.
As methotrexate can affect the immune system, liver and kidneys, before starting it you will need blood tests. These will also need to be monitored whilst you are taking it. These will be at 2 weeks, 4 weeks and 6 weeks after starting it, then once a month for 3 months and then every 3 months for the time that you are on the medication.
You will also require a chest X-ray before starting methotrexate to make sure that you have no underlying damage to your lungs. If you are a smoker it would be worthwhile trying to cut down and stop to prevent any risk of damage to your lungs.
The initial supply of tablets or injections for 8 weeks will be given from the hospital and rheumatology team, who will monitor your first 3 blood tests and symptoms. After this your GP will continue to look after your prescriptions and blood monitoring.
You will be given the phone number of the rheumatology nurse specialists when you start on methotrexate, if you have any further questions that are not answered here, or you are struggling with side effects then you can contact the team.
Sometimes taking methotrexate can cause side effects, these can include:
- Nausea, vomiting and diarrhoea
- Mouth ulcers
- Minor hair loss and thinning
- Shortness of breath
If you are struggling with feeling sick, anti sickness tablets can be tried by your GP to see if this helps. If this is not helping, then changing to a weekly injection can help.
In rare cases, methotrexate can cause an allergic reaction in the lungs called pneumonitis. This can cause shortness of breath and a dry cough. If you get any symptoms, it is important to speak to your GP or rheumatology team as you may require a repeat chest X-ray or breathing tests.
As the immune system is targeted by the methotrexate, it is important to get your blood tests checked. Should you develop signs of infection, stop taking your methotrexate and speak to your GP as you may require antibiotics. Once you are feeling better and have completed any antibiotics you can restart taking your methotrexate.
Methotrexate can also affect the blood cell counts, liver and kidneys. If you notice any yellow discoloration to your skin or eyes, bruising and bleeding you should let your doctor know.
If you develop, or come into contact with anyone with shingles or chickenpox, you should speak to your doctor as you may need treatment and to stop taking your methotrexate temporarily.
Cautions of use
Interactions with other medications
- Antibiotics called trimethoprim, septrin and co-trimoxazole should be avoided as these can exacerbate the effects of methotrexate on the blood cells.
- An asthma drug called theophylline can affect blood levels of methotrexate and will need monitoring closely.
Contraindications with other conditions
- As in rare occasions methotrexate can cause inflammation in the lungs, it is often not used if you have underlying lung diseases.
- If you have underlying liver diseases, methotrexate may not be safe to use.
- In minor surgery, methotrexate can usually be continued, however you should always check with your doctor and surgical team.
During pregnancy or breastfeeding
- Methotrexate is not safe to be taken when trying for a baby, pregnant or breast feeding.
- If you are planning a family, methotrexate should be stopped 3 months before you start trying.
- There’s no evidence methotrexate affects men who are trying to conceive a child.
- Alcohol and methotrexate can both affect the liver. It is recommended to take alcohol within moderation, following the guidelines of less than 14 units weekly.
- Flu and the pneumonia are safe and recommended whilst taking methotrexate.
- The shingles vaccine can be given if you are on lower doses of methotrexate and should be discussed with your doctor.
- Live vaccines should be discussed with your doctor.
Versus Arthritis: http://www.versusarthritis.org