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.