| METHOTREXATE |
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What is it? Methotrexate (MTX) is a folate acid antagonist. It basically blocks an essential step in DNA synthesis and causes a reduction in cell reproductive abilities. This is why it is commonly used alongside other drugs in cancer treatment (chemotherapy) because it can reduce cancerous cell growth and tumours.
Who is it for? MTX is prescribed for severe, disabling psoriasis that is not adequately responsive to other forms of treatment and is particularly beneficial for those with psoriatic arthritis. How is it taken? MTX is given orally as a single dose once a week. Tablets come in 2.5mg form and it is important, even when taking large doses, to take individual tablets to make up your weekly dose. This allows the correct dosage to be taken as you will carefully check and measure it out - as a toxic drug, it is vital you do not take more than the prescribed amount! MTX can also be given intramuscularly and intravenously if there is a history of gut problems. However, there is little evidence this is available in the UK. How much do I take? A test dose of 2.5mg to 5mg is normally given to detect those who may have a sensitivity to the drug. If all goes well and the monitoring shows normal organ and blood function, this can increase in 2.5mg increments up to 30mg per week. However, the average maintenance dose is 10 to 25mgs per week. You may find you need to up your dose every so often to maintain clearance of P. However, when adequate clearance is achieved, it is normal to taper the dose by 2.5mg per month. What are the side effects and contra-indications? MTX has a side effects list as long as your arm! The most common side effects are nausea, vomiting, diarrhoea, headaches and fatigue. These normally occur up to three days after the single dose in those affected. However, as with all drugs, some will not suffer any side effects, some one or two and some all of the above! We are all individuals and you cannot know how you will cope with MTX until you are taking it. Moreover, the higher the dose the more likely you are to suffer one or more of the side effects - particularly nausea and fatigue. There are things you can do to combat and lessen some of these:
MTX interacts with many other drugs. This list is pretty long too and it is vital that you mention you are taking it if ever prescribed any other drug by a doctor or buying something over the counter from a chemist. This includes items such as cold and cough remedies - aspirin is contra-indicated! As MTX affects cell structure, it is vital a female does not get pregnant whilst using it and for at least three months after stopping treatment. Most doctors will perform a pregnancy test if there is a chance of pregnancy before starting on MTX. It is also vital good contraception is used throughout the use of the drug. Similarly, it is advisable for male MTX users to refrain from fathering children for the duration of treatment. What monitoring do I need? It is vital that you receive comprehensive and careful monitoring whilst taking MTX. These tests are there to protect you and should indicate a problem long before it actually becomes one. Baseline Monitoring:
Follow-up Monitoring: FBC, LFT, U&E and creatinine every week after initial dosage, then every four to eight weeks. Repeat of these seven days AFTER dose escalation - then back to every four to eight weeks as above. As the liver is at greatest risk from MTX treatment, a good doctor will also perform an 'assay of amino propeptide of type III procollagen' or a PIIINP test every three to six months. This blood test shows up tiny negative changes to the liver in a way the LFT cannot and can, in some cases, show up the need for a liver biopsy. Some doctors believe this test can actually stop the need for a routine liver biopsy after a cumulative dose of 1.5gms, though others like you to have one anyway and at 1.5gm intervals after. Obviously, as MTX affects the liver, alcohol is best avoided, particularly around the days you take it. However, the odd glass of wine or beer is acceptable as long as it is just that! If all this monitoring is performed correctly, any negative affects of the drug are reversible if caught and dealt with at an early stage. There are many threads and posts, including questions and answers perhaps not dealt with above and experiences of those . SJ June 2003 |
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