RESUMO
In the present work, an experimental study of the possible interactions between digoxin and two opioids [pentazocine and butourphanol] on the cardiovascular system was conducted both in vivo and in vitro. l. V. injection of pentazocine or butorphanol produced a significant hypodigitalised as well as in intravenously or orally digitalized dogs, with no effect on electrocardiographic tracings. Each of these opioids when administered alone or with digoxin infusion to the isolated rabbit heart was found to induce significant decrease of the myocardial contractility but no changes in the mean coronary flow. The possible mechanisms underlying these interactions were discussed, and it could be concluded that pentazocine or butorphanol must be used cautiously during digitalis therapy owing to their potential negative inotropic and hypotensive effects