Methotrexate

Question 1

What are indications for the use of methotrexate?

Answer 1

• Rheumatoid arthritis
• Chemotherapy
• Psoriasis

Question 2

What is the mechanism of action of methotrexate?

Answer 2

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

Question 3

What are adverse effects of methotrexate?

Answer 3

• Gastrointestinal upset
• Rash
• Myelosuppression
• Alopecia
• Cirrhosis
• Pulmonary fibrosis
• Renal impairment (high dose therapy)

Question 4

What are contraindications you would check for before starting someone on methotrexate?

Answer 4

• Hepatic impairment
• Pregnancy and breast feeding
• Active infection
• Immunodeficiency

Question 5

When should cuation be used when prescribing methotrexate?

Answer 5

• Peptic ulceration
• Pleural effusion or ascites
• Renal impairment
• Porphyria

Question 6

What drugs interact with methotrexate?

Answer 6

• Aspirin
• NSAIDs
• Folate antagonists - trimethoprim, co-trimoxazole
• Ciclosporin

Question 7

How often should methotrexate be given?

Answer 7

Once weekly tablets, same day each week unless used as chemo

Question 8

Is methotrexate teratogenic?

Answer 8

YEs

Question 9

What monitoring would you want to do for someone on methotrexate?

Answer 9

Regular FBC, U+E’s and LFTs

1. Before starting treatment
2. 1-2 weekly until treatment established
3. 2-3 montlhy once established

Question 10

What effects does methotrexate overdose cause?

Answer 10

• Renal impairment
• Hepatotoxicity
• Headache
• Seizures
• Coma

Question 11

What would you administer to treat methotrexate toxicity?

Answer 11

Folinic acid

Question 12

What should be prescribed with methotrexate?

Answer 12

Folic acid for 6 days that methotrexate is not taken - limits adverse effects

Question 13

How long does it take for methotrexate to be effective?

Answer 13

3-12 weeks

Question 14

What features would you want to warn someone about who is on methotrexate?

Answer 14

• Infection
• Unexplained bruising

Question 15

What should you prescribe with methotrexate?

Answer 15

Folic acid 5mg - another day of the week