Methotrexate Flashcards
What class of drug is methotrexate?
DMARD
What is the action of methotrexate?
Methotrexate is a dihydrofolate reductase inhibitor - it inhibits the conversion of dihydrofolate to it’s active form, tetrtahydrofolate, suppressing the immune system
What are the indications for methotrexate?
Crohn’s disease
Rheumatoid arthritis
Neoplastic disease
Severe psoriasis
What are the common side effects of methotrexate?
Nausea
Diarrhoea
Alopecia
Stomatitis/mucositis
What are the important side effects of methotrexate?
Myelosuppression - leucopenia and neutropenia
Hepatotoxicity
Teratogenicity
Pericarditis
Pulmonary fibrosis
What are the cautions for methotrexate?
Ulcerative colitis
Blood disorders
Peptic ulcer disease
Photosensitivity
Dehydration
Pregnancy and breastfeeding Alcohol abuse and liver cirrhosis
What are the contraindications to methotrexate?
Active infection
Ascites
Immunodeficiency syndromes
What does methotrexate interact with?
Trimethoprim - risk of pancytopenia
Co-trimoxazole - risk of pancytopenia
NSAIDs - may reduce methotrexate excretion
Clozapine - agranulocytosis
Acitretin - increases plasma methotrexate conc
Live vaccines - risk of infection due to immunosuppression
How is methotrexate given?
It is given by mouth, SC or IM injection once weekly on the same day.
In neoplastic disease it can be given IV or intra-arterial infusion
What should be prescribed alongside methotrexate?
Folic acid - 5mg. To be taken once weekly on a different day to the methotrexate.
What are the monitoring requirements for patients on methotrexate?
Baseline tests - FBC, U&E, LFT, ESR and CRP
Patients should have LFT, U&E and FBC every 1-2 weeks until therapy is stabilised, and then every 2-3 months after
Patients should have ESR and CRP checked every 3 months
What information should be patients be given?
Females must not take this medication during pregnancy - both men and women should stop methotrexate for 6 months before beginning to try and conceive
Immediately report any features of blood disorder (sore throat, bruising, ulcers) or liver toxicity (nausea, vomiting, abdominal pain, dark urine)
Patients should be advised to avoid exposure to UV light
Patients should be advised to avoid excessive OTC use of ibuprofen and aspiri.
What other medications are in the same class as methotrexate?
Antimetabolites
- Azathioprine
- Mercaptopurine
- Cladribine
- Fluorouracil
