Methotrexate

Question 1

What is the MOA of methotrexate?

Answer 1

It inhibits dihydrofolate reductase.

Dihydrofolate reductase is essential for the synthesis of purines and pyrimidines.

Question 2

What are some side effects of methotrexate?

Answer 2

• Mucositis
• Myelosuppression
• Pneumonitis
• Pulmonary fibrosis
• Liver cirrhosis

Question 3

What advise should be given to women who take methotrexate?

Answer 3

Avoid pregnancy for at least 3 months after treatement has stopped.

Question 4

What advise shold be given to men taking methotrexate?

Answer 4

Men using methotrexate need to use effective contraception for at least 3 months after treatment.

Question 5

Is methotrexate taken weekly or daily?

Answer 5

Once weekly

Question 6

What blood tests should be regularly monintored when using methotrexate?

Answer 6

FBC, U&Es and LFTs before starting and every 2-3 months.

Question 7

What else should be prescribed alongside methotrexate and how often?

Answer 7

Folic acid 5mg Once weekly. (>24 hours AFTER methotrexate dose)

Question 8

What is the starting dose of methotrexate?

Answer 8

Usually about 7.5mg

Question 9

What is the only strength tablet of methotrexate?

Answer 9

2.5mg tablets.

(Helpful in order to prevent accidental overdoses)

Question 10

What other drugs should be avoided when prescribing methotrexate & why?

Answer 10

Trimethoprim or cotrimoxazole.

Concurrent use increases the risk of marrow dysplasia