Methotrexate Flashcards
What are indications for the use of methotrexate?
- Rheumatoid arthritis
- Chemotherapy
- Psoriasis
What is the mechanism of action of methotrexate?
Inhibits dihydrofolate reductase, which converts dietary folic acid to tetrahydrofolate. This is required for DNA and protein synthesis, so lack of it prevents cellular replication. Actively dividing cells are particularly sensitive to the effects of methotrexate, accounting for its efficacy in cancer. It also has anti-inflammatory and immunosuppressive effects
What are adverse effects of methotrexate?
- Gastrointestinal upset
- Rash
- Myelosuppression
- Alopecia
- Cirrhosis
- Pulmonary fibrosis
- Renal impairment (high dose therapy)
What are contraindications you would check for before starting someone on methotrexate?
- Hepatic impairment
- Pregnancy and breast feeding
- Active infection
- Immunodeficiency
When should cuation be used when prescribing methotrexate?
- Peptic ulceration
- Pleural effusion or ascites
- Renal impairment
- Porphyria
What drugs interact with methotrexate?
- Aspirin
- NSAIDs
- Folate antagonists - trimethoprim, co-trimoxazole
- Ciclosporin
How often should methotrexate be given?
Once weekly tablets, same day each week unless used as chemo
Is methotrexate teratogenic?
YEs
What monitoring would you want to do for someone on methotrexate?
Regular FBC, U+E’s and LFTs
- Before starting treatment
- 1-2 weekly until treatment established
- 2-3 montlhy once established
What effects does methotrexate overdose cause?
- Renal impairment
- Hepatotoxicity
- Headache
- Seizures
- Coma
What would you administer to treat methotrexate toxicity?
Folinic acid
What should be prescribed with methotrexate?
Folic acid for 6 days that methotrexate is not taken - limits adverse effects
How long does it take for methotrexate to be effective?
3-12 weeks
What features would you want to warn someone about who is on methotrexate?
- Infection
- Unexplained bruising
What should you prescribe with methotrexate?
Folic acid 5mg - another day of the week
