DPI 201-106 is a new oral inotropic agent that exerts its effects through a novel mechanism of action, namely, by enhancing sensitivity of myofilaments to calcium and prolonging inward sodium current. In a double-blind, randomized, placebo-controlled fashion, single oral doses (80 and 100 mg) of DPI 201-106 were administered to 15 patients with severe congestive heart failure. Dose-dependent increases in cardiac index (25%, p = 0.016), left ventricular stroke work index (24%, p = 0.018), left ventricular stroke volume index (32%,p = 0.005) and QTc interval (7%, p = 0.009) were observed. Significant effects on heart rate and systemic arterial pressure were not observed. Positive correlations of QTc interval with DPI plasma level (r = 0.64, p = 0.0001), stroke work index (r = 0.47, p = 0.0001) and ventricular ectopic activity on ambulatory electrocardiography (r = 0.49, p = 0.0001) were observed. Maximum changes occurred approximately 3 to 4 hours after ingestion and lasted more than 8 hours. Plasma drug levels were consistent with a 2-compartment model exhibiting first-order absorption and elimination kinetics. DPI 201-106 produced hemodynamic improvement in patients with severe congestive heart failure.