Methotrexate (MTX).

Folic acid antagonist.

Reduces DNA production, hence cell turnover esp fast growing cells.

Indications

  • Inflammatory AI conditions (DMARD).
  • As chemotherapy.
  • In obstetrics for trophoblastic disease, ectopic or missed miscarriage.

Dose 5-20mgs po, s/c usually weekly.

Take in morning.

Taking folic acid is recommended. No consensus on when and how much – recommendation is 1mg a day (ideally a weekly 5mgs day after MTX). 

Leucovorin can rescue.

Comes in 2.5mgs and 10mgs – BEWARE of which.

Lower dose if renal compromise / elderly.

Dose titration by 2.5gs every 6 weeks.

Monitoring of levels not required.

But needs monitoring policy for bloods for those on it.

2 weekly for first 6 weeks. Then every 6 weeks for first year. Then every 3 months.

Interactions

Trimethoprim - increase in aplastic risk.

C/I in pregnancy whilst on for 3/12 after stopping and avoid in B/F.

Avoid LIVE vaccines.

Zoster / varicella exposure – consider passive cover with immunoglobulins.

Does not have to stop for surgery.

Adverse effects of MTX include

  • Buccal, intestinal and respiratory epithelium. Bone marrow. Malignant cells. Trophoblastic tissue.
  • Mucositis / stomatitis / Conjunctivitis - FA helps this++.
  • Myelosuppression
  • GI upset
  • Pulmonary – methotrexate pneumonitis.
  • Neurological

 

Alopecia, skin burning, photosensitivity.