Chapter 10 - DMARDs

Question 1

What is the MOA of methotrexate?

Answer 1

antimetabolite which acts principally by competitively inhibiting the enzyme, dihydrofolate reductase. In the process of DNA synthesis and cellular replication, folic acid must be reduced to tetrahydrofolic acid by this enzyme, and inhibition by methotrexate interferes with tissue cell reproduction. Actively proliferating tissues such as malignant cells are generally more sensitive to this effect of methotrexate.

Question 2

Why is folic acid given in those taking methotrexate?

Answer 2

Reduce the muscosal and GI side-effects associated with methotrexate use and myelosupression

Question 3

In patients taking methotrexate, which side-effects in particular should they be warned about and should report if develops?

Answer 3

1) Blood dyscrasias - report any signs of infection (e.g sore throat, mouth ulcers, bruising)
2) liver toxicity - abdominal pain, yellowing of eyes/skin, darker urine, N+V
3) respiratory effects - SOB