Trimethoprim/Sulphamethoxazole: Long‐term Therapy and Folate Levels

Drugs alleged to cause megaloblastic anaemia are briefly discussed. In a series of patients treated for one year with Septrin (trimethoprim/sulphamethoxazole) there was no evidence for the production of anaemia, and the serum and red cell folate levels did not fall. Eight patients are discussed whose megaloblastic anaemia was thought by their physicians to have been induced by the TMP/SMX combination. In every instance an alternative explanation was found. Reports in the literature of alleged adverse effects of the drug combination on human folates are reviewed. Naturally, it would be inadvisable to give any folate antagonist to a subject already suffering from folate deficiency.