BACKGROUND As chronic Chagas disease does not have a definitive treatment, the development of alternative therapeutic protocols is a priority. Dipyridamole (DPY) is an alternative to counteract the pathophysiological phenomena involved in Chagas cardiomyopathy. OBJECTIVE To evaluate the therapeutic efficacy of DPY associated with nifurtimox (Nfx) in epimastigote axenic cultures and in mice with acute Chagas disease.

METHODS NMRI adult male mice were divided into nine groups:

three healthy and six Trypanosoma cruzi-infected groups. Mice received vehicle, Nfx or DPY, alone or combined. The doses assayed were Nfx 10 and 40 mg/kg and DPY 30 mg/kg. The treatment efficacy was evaluated by clinical, electrocardiographic, parasitological, biochemical and histopathological methods. FINDINGS In vitro, DPY and Nfx had a trypanocidal effect with IC50 values of 372 ± 52 and 21.53 ± 2.13 µM, respectively; DPY potentiated the Nfx effect. In vivo, Nfx (40 mg/kg) with or without DPY had a therapeutic effect, which was reflected in the 84-92% survival rate and elimination of parasitaemia and heart tissue amastigotes. Nfx (10 mg/kg) had a subtherapeutic effect with no survival and persistence of amastigotes, inflammation and fibrosis in heart tissue; adding DPY increased the survival rate to 85%, and all tested parameters were significantly improved. MAIN CONCLUSION DPY has a trypanocidal effect in vitro and enhances the Nfx therapeutic effect in an in vivo murine model.