DR Medhat MRCP

Methotrexate :
Drugs used in rheumatology
- Methotrexate is an antimetabolite which inhibits dihydrofolate reductase, an enzyme
essential for the synthesis of purines and pyrimidines.
• Indications
4. Rheumatoid arthritis
5. Psoriasis
6. Acute lymphoblastic leukaemia
• Adverse effects
6. Mucositis
سؤال 7. Myelosuppression/folate deficiency macrocytic anemia
8. Pneumonitis
9. Pulmonary fibrosis
10.Liver cirrhosis
• Methotrexate & pregnancy
Women (& men )should avoid pregnancy for at least 3 months after treatment
سؤال stopped. has
• Prescribing methotrexate
Methotrexate is taken weekly, rather than daily.
The starting dose of methotrexate is 7.5 mg weekly (source: BNF)
CBC, RFTand LFTs need to be regularly monitored (before starting ,then weekly
till therapy stabilized then CBC /1-2 months, LFT / 3 months, RFT /6 months.
Folic acid 5mg once weekly should be co-prescribed, taken more than 24 hours
after methotrexate dose
Only one strength of methotrexate tablet should be prescribed (usually 2.5 mg)
- Avoid prescribing trimethoprim or cotrimoxazole concurrently - increases risk of
marrow aplasia.
Sulphasalazine (salazopyrine®) :
• Side effects : B.M depression (pancytopenia), allergy ,macrocytosis , hepatotoxicity
& azospermia
• Monitoring : WBCs < 3.5
B. CBC monthly for 3 months : → hold if Neutrophils < 2
Platelets < 150
→ if normal → Check CBC every 3 months X 1 year
B. LFT monthly for 3 months : → hold if ALT or AST ↑ ≥ double upper normal.
→ If normal → Check LFT every 3 months X 1 year
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N.B : In acute infection, most DMARDs
(except hydroxychloroquine) should be
discontinued until the infectious
سؤال process has resolved