Placental transfer of pyrimethamine studied in an ex vivo placental perfusion model

Pyrimethamine is used as and anti-infectious agent because of its antifolat e properties. Its action is synergistic with that of dapsone and sulfamides on Toxoplasma gondii, The goal of the present study was to evaluate the pl acental transfer of pyrimethamine in an ex vivo model of perfused human pla cental cotyledon at term. Human placentas were perfused according to the sl ightly modified method of Schneider. The pyrimethamine fetal transfer rate was approximately 30%, while cotyledon clearance was about 1.8 ml/min. The placental transfer of pyrimethamine seems to be independent of the maternal concentrations of pyrimethamine, suggesting passive diffusion mechanisms o r a nonsaturable active transport at the tested concentrations. Copyright ( C) 2000 S. Karger AG, Basel.