Effects of the prilocaine and of the association of prilocaine with different vasoconstrictors on the isolated hearts of rats.

This study aimed to observe the effects of prilocaine chloridate (P) and the associations of P with felypressin (P+F), and epinephrine (P+E) on the heart rate and force of contraction on the isolated hearts of rats. The hearts were perfused according to Langendorff's method. The experiments were performed with the following substances: prilocaine (P), felypressin (F), and epinephrine (E). P was used in doses of 1.25, 2.5, and 5.0 mg. The same doses of F and P (1.0, 1.5 and 3.0 microg) were used in association with the P, respectively. Right after the application of the three doses of P, a reduction in the force of contraction was observed, with higher intensity at a higher dose, which led to cardiac arrest. A similar result was obtained with the administration of the three associations of P+F. Also the application of the three associations P+E resulted in a reduction of the force of contraction, that was, however, less intense with the associations of 1.25 mg P + 1.0 microg E and 2.5 mg P+1.5 microg E, as compared to the same doses of P alone and P+F. The two higher doses of P and P+F on the heart rate elicited a significant reduction in relation to the control, but with the associations of P+E no alterations were observed, with any one of the doses used. The results obtained in the present study suggest that an association of P and E must be used in local anesthesia, since epinephrine may well protect the heart from the depressive effects of the anesthetic salts.