Serum levels of creatine kinase-MB (CK-MB) in C57BL/6 mice infected with T. cruzi Y strain. The animals were treated with benznidazole (B) at 100, 50, 25, or 5 mg/kg alone or combined with suramin (S; 20 mg/kg) for a period of 15 days after confirmation of the infection (4 days after inoculation). NI, noninfected controls; INF, infected without treatment. Cardiac samples were collected 24 h after the last treatment. All animals that survived were investigated (NI, n = 10; INF, n = 6; B100, n = 10; S20, n = 4; B100 + S20, n = 10; B50 + S20, n = 8; B25 + S20, n = 6; B5 + S20, n = 5). The box represents the interquartile interval with the median indicated (horizontal line), and the whiskers represent the superior and inferior quartiles. Data are representative of the second experimental replicate from two independent studies with similar results. Different letters (a to f) denote a statistically significant difference among the groups (P < 0.05), and groups with a common letter are not statistically significantly different (P > 0.05).