The aim of the present study was to evaluate the in vitro activity and cytotoxicity of meglumine antimoniate microspheres produced by spray drying on Leishmania infantum and the effect of the excipients used in them. The parasite strain shows sensitivity to the meglumine antimoniate microspheres prepared. All the antimony IC50 values from encapsulated meglumine antimoniate (3.80 +/- 0.34 to 9.53 +/- 0.70 microg SbV/ml for promastigotes assay) are considerably lower compared to the mean value of IC50 in Glucantime solution (112 +/- 12.74 microg SbV/ml). Interesting IC50 values for the excipient chitosan (112.64 +/- 0.53 mg/ml for promastigotes and 100.81 +/- 26.45 mg/ml for amastigotes) were obtained (without cytotoxic activity), whereas the rest of the excipients did not show any activity. This new delivery system could offer a new pharmacological tool for the treatment of leishmaniosis that reduces the doses required, lowering toxic side effects because of meglumine antimoniate.