Toxicity of Trimethoprim-Sulphamethoxazole in Patients with Megaloblastic Haemovoiesis

Abstract

Four consecutive patients with megaloblastic anaemia who also received therapy with trimethoprim-sulpha-methoxazole all showed poor responses to specific haematinic therapy. This was attributed to trimethoprim, which suppressed reticulocyte responses in three cases and produced a pancytopenia in two and a falling haemoglobin with neutropenia in a third. A fourth patient, with pernicious anaemia, had a satisfactory reticulocyte response but experienced no clinical benefit until after withdrawal of trimethoprim. Trimethoprim seems not to be a safe form of therapy in patients with a megaloblastic process; many of the toxic reactions reported with this drug may be on the basis of an unrecognized megaloblastic form of haemopoiesis. © 1972, British Medical Journal Publishing Group. All rights reserved.