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Methotrexate

Page history last edited by PBworks 18 years, 8 months ago

METHOTREXATE TREATMENT

INFORMATION FOR GENERAL PRACTITIONERS

 

The aim of treatment is to suppress disease activity and preserve joint function in the Inflammatory Arthropathies.

 

DOSAGE - As advised by Rheumatologist :

Either

10 mg, doubling to 20 mg after 8 weeks unless significant improvement in disease.

or (in the elderly, frail or very thin)

7.5 mg as a single dose once weekly, doubling to 15mg after 3 months, and increasing by 5mg every 3 months thereafter until a maximum of 25mg weekly, if lower doses ineffective.

 

Folic Acid 5 mg should be prescribed once weekly, taken the day after the Methotrexate dose. This reduces adverse effects.

 

MONITORING PROCEDURE

FBC, ESR AND LFT fortnightly until 6 weeks after last dose increase, then monthly

U&Es - 6-12 monthly

withhold and inform Rheumatology Department if any of the following:

 

Neutrophils < 2.0 x 109/l

Platelets < 150 x 109/l

> 2 fold increase in AST, ALT (from upperlimit)

Unexplained fall in Albumin

Rash or oral ulceration

New or increasing dyspnoea or cough

MCV > 105

 

Significant deterioration in renal function - reduce dose

Abnormal bruising or sore throat - withhold until FBC available

Duration of Treatment and Time to Response

Treatment is continued indefinitely providing it remains effective and there are no significant side effects. Methotrexate takes about 2-3 months to become effective. During this period there are likely to be continued symptoms or signs of disease activity. it is reasonable to use IM Depo Steroid (Kenalog 40 mg or Depo Medrone 80 mg) up to monthly, depending on the requirements of the individual patient. The dose required is small (eg monthly Kenalog 40 mg = 1.6 mg Prednisolone daily). If IM steroids are still required three months after starting treatment the Methotrexate should be increased.

 

Flares

Unfortunately disease modifying drugs will not prevent all flares. These can be managed with IM Depo Steroid as outlined above. If flares become more frequent, or the disease fails to settle between flares, the dosage should be increased, or an alternative discussed with the Rheumatologist.

 

Contraindications

Known hypersensitivity to Methotrexate. Alcoholism, severe renal, hepatic or haematological impairment. Immunodeficiency, pregnancy, breast feeding, live vaccines, co-prescription of folate antagonists eg Co-trimoxazole.

 

 

Warnings

Caution in renal impairment, peptic ulcer, ulcerative colitis, ulcerative stomatitis, diarrhoea, debility. Avoid conception for six months after treatment stops. Patients should be cautioned to contact GP immediately if they develop a cough or dyspnoea. Treatment should be interrupted if there is marked GI upset usually severe stomatitis.

 

 

Interactions

Methotrexate excretion may be affected but actual toxicity is exceedingly rare when co-prescribed with salicylates, sulphonamides (including Trimethoprim), diuretics, hypoglycaemics, diphenylhydantoins, tetracyclines, Chloramphenicol, P-aminobenzoic acid and NSAIDs.

 

 

Side effects

 

 

Mucocutaneous - urticaria, erythematous, purritis, alopecia, severe or increasing

oral ulceration

 

Haematological - neutropenia, thrombocytopenia and rarely aplastic anaemia

 

Gastrointestinal - GI UPSET, enteritis

 

Other - acute tubular necrosis, interstitial pneumonitis, liver fibrosis,

depression, irritability

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