Methotrexate

PI - Methotrexate

Dose

Commenced at 7.5mg WEEKLY.
Dose may be increased upto 20mg WEEKLY

Commonest problem is diarrhoea. Some change in bowel habit is common upto 30%. If tolerable, leave individual on the drug. If frequency of bowel action is not acceptable stop Methotrexate.

Important interactions

• Do not use with other myelosuppressive drugs. Note patients who have severe RA may now be placed on combinations of SLA with specialist advice.
• Do not use with Aspirin, except cardiovascular protective dose of 75mg daily.
• Do not use with sulphonamides.
• Use with caution in patients who drink alcohol regularly.
  

Monitoring

Blood: FBC and LFT's weekly for 1 month then monthly ESR or plasma viscosity (not mandatory but helps to monitor disease)
Urine: Not necessary as a routine.

When to act on results

Contact Rheumatolgy Unit help line on ext 2314

Services - Rheumatology

1. If total WCC or absolute neutrophil count falls -
   1. from within normal range to below the lower range value.
   2. for 3 consecutive tests (even within the normal range when absolute value falls by 3 x 10-9 cells cm-2).
2. If platelets fall -
   1. from within normal range to below the lower range value.
   2. for 3 consecutive tests (even within the normal range when absolute value falls by 100 x 10-9 cells cm-2).
3. For liver function studies -
   1. if liver enzymes (AST, GGT or ALT) rise over 3 consecutive tests to more than 2x the upper limit of normal.
   2. Alkaline phosphatase (ALP). This enzyme acts as an acute phase response and so reflects disease activity in a similar way to the ESR. If ALP rises to 3x normal or base line value, please contact the rheumatology department.
4. Chest radiograph should be checked before treatment is started. (This is to ensure that there is no pre-existing fibrotic lung disease. Methotrexate is rarely associated with pulmonary fibrosis. If there is no base line CXR, then assessment of pulmonary fibrosis is impossible.

Document Information
Expiry Date: 11/04/04
Author: Kennedy Tom Dr
Organisation: Arrowe Park Hospital