In this study we intend to evaluate the immune and therapeutic responses of patients with visceral leishmaniasis N-acetylcysteine (NAC) as an adjuvant to standard treatment with pentavalent antimony, compared to treatment with antimonial only through a blind randomized clinical trial. Our hypothesis is that patients treated with NAC associated with pentavalent atimonial have a rapid changing of the immune responses, towards TH1, and clinical improvement when compared to patients who will use only the standard treatment