The possible additive effect of ethanol (EtOH) on verapamil on isolated papillary muscle of cats weighing 1200-1500g kept in oxygenated Ringer Locke solution was studied. Papillary muscles were dissected from the right ventricle, mounted vertically in an acrylic support and stimulated electrically driven at a constant rate by means of silver at 37oC (pH=7.4). We studied the effect on peak tension development (PTD) of verapamil (5.4 X 10-4 mM) and two EtOH concentrations (48.6 and 97.2 mM) in cat papillary muscle bathed in a normocalcic medium (2.2 mM) of Ringer-Locke solution. EtOH in both concentrations potentiated the decrease of PTD (inotropic effect), (-53.31±2.07% and -60.00±3.50%, respectively) compared to verapamil previously incubated in bath (-38.1±2.26%). It was concluded that verapamil induces a decrease in myocardial contraction by a posterior consumption of sufficient EtOH enough to put the patient in the risk of a lamentable induction of cardiac failure.