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Methotrexate

(British) UK Trade name products which contain methotrexate include: (Emtexate Vials) (Emtexate PF) (Arthritex Tabs) (Maxtrex)

(American) US Trade name products which contain methotrexate include: (Folex) (Mexate) (Rheumatrex) (Folex Pfs) (Mexate-Aq)

INDICATION

This chemotherapeutic agent has been used to treat a variety of conditions including psoriasis and rheumatoid arthritis. It is also useful in the treatment of leukaemia, lymphomas, and other cancers. The "antidote" for this medication is folinic acid and it is used to reverse the toxic effects associated with this medication.

SIDE EFFECTS

Low white blood cell counts, low platelet counts, inflammation of the mouth, diarrhoea, intestinal perforation, kidney toxicity, elevated liver enzymes, rash, increased blood uric acid, and hair loss. Common side effects include: black stools (GI bleeding), bloody vomit, sore throat, fever, mouth sores, nausea, vomiting, and abdominal pain.

INTERACTIONS and PRECAUTIONS

  1. Folic acid derivatives can antagonize the effects of methotrexate.
  2. DO NOT use with nonsteroidal anti-inflammatory agents, phenylbutazone, aspirin, or sulpha drugs; can increase toxicity.
  3. Use cautiously in those with peptic ulcer, ulcerative colitis or elderly.
  4. Watch for signs of bleeding (bleeding gums, bruising).
  5. Watch for signs of infection (fever, sore throat, fatigue).
  6. Use with anticoagulants (Warfarin) can increase the anticoagulant effect.
  7. Use with phenytoin may increase risk of methotrexate toxicity.
  8. Use with clozapine can increase the toxic effect on bone marrow.
  9. Use with diclofenac may increase methotrexate toxicity.
  10. Use with fluorouracil can decrease methotrexate effect.
  11. Use with folic acid may decrease methotrexate effect.
  12. Use with folinic acid can decrease methotrexate toxicity.
  13. Use with nonsteroidal anti-inflammatories (e.g. ibuprofen) may increase methotrexate toxicity.
  14. Use with probenecid may cause methotrexate toxicity.
  15. Use with pyrimethamine may increase methotrexate toxicity.
  16. Use with aspirin and other salicylates may cause methotrexate toxicity.
  17. Use with sulpha drugs (e.g. Septra) or tetracyclines may cause methotrexate toxicity.

USUAL DOSE

Adults: dose varies with condition being treated; oral 15-30 mg per day for five days.

Paediatrics: individualised by doctor.

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