Interactions between trimpex(trimethoprim) and Methotrexate sodium preservative free (methotrexate)
methotrexate and trimethoprim (Major Drug-Drug)
GENERALLY AVOID: The concomitant use of methotrexate and trimethoprim may potentiate the risk of severe myelosuppression and megaloblastic anemia due to additive or synergistic effects involving folate antagonism. The interaction has been reported primarily with sulfamethoxazole-trimethoprim but has also occurred with trimethoprim alone. Most cases involve the elderly, often in association with renal impairment. In one case report, an 81-year-old woman receiving low-dose methotrexate (7.5 mg/week) for rheumatoid arthritis developed fatal pancytopenia following the addition of trimethoprim. The dosage of trimethoprim had been 100 mg/day for nearly two months but was increased to 200 mg/day due to suspected urinary tract infection one week prior to hospitalization. The patient's bone marrow failed to recover despite treatment with folinic acid and granulocyte colony stimulating factor, and she died of bronchopneumonia one week after admission.
MANAGEMENT: The concomitant use of trimethoprim and methotrexate, even at low dosages, should generally be avoided if possible. If the combination is given, close monitoring for hematologic toxicity is recommended, particularly in the elderly. Folate supplementation may be necessary in some cases. Patients should be advised to notify their physician if they experience signs and symptoms of bone marrow depression or anemia such as fever, chills, sore throat, easy bruising or bleeding, pallor, dizziness, fatigue, lethargy, sore mouth or tongue, and tingling in hands or feet.
