[Comparative controlled study on the use of benznidazole, nifurtimox and placebo, in the chronic form of Chagas' disease, in a field area with interrupted transmission. I. Preliminary evaluation].

A controlled clinical trial was carried out to evaluate the therapeutic efficacy and tolerance of nifurtimox and benznidazole in patients with chronic Chagas' disease. All patients had immunofluorescence and complement fixation reactions positives for T. cruzi antibodies and at least two xenodiagnoses positives in three performed before treatment, and they were submitted to clinical examinations, ECG and X-ray of the heart and esophagus. Of 77 patients studied, 27 were treated with nifurtimox and 26 with benznidazole in the dosage of 5 m/kg/day for 30 consecutive days, and 24 received a placebo in tablets similar to benznidazole. From the 77 patients, 64 (83.1%) accomplished the treatment: 23 (88.4%) with benznidazole, 19 (70.3%) with nifurtimox and 22 (91.6%) with placebo. The patients were evaluated, clinically, serologically and parasitologically (six xenodiagnoses within one year after treatment). The benznidazole group showed only 1.8% of positive xenodiagnoses post-treatment, the nifurtimox 9.6% and the placebo 34.3%. All serologic reactions continued positive and there were no clinical, ECG or X-ray changes one year after treatment.