Papers And Originals

Toxicity of Trimethoprim-Sulphamethoxazole in Patients with Megaloblastic Haemopoiesis

Br Med J 1972; 1 doi: (Published 11 March 1972) Cite this as: Br Med J 1972;1:651
  1. I. Chanarin,
  2. J. M. England


    Four consecutive patients with megaloblastic anaemia who also received therapy with trimethoprim-sulphamethoxazole 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.