ICI-118, 551 Withdrawal Syndrome in Isolated Rat Heart and Aorta Tissue

In this study, performed at the Department of Pharmacology of the Karadeniz Technical University School of Medicine, the effects of sudden withdrawal of a ß2-selective blocker agent, ICI-118, 551, after 21 days of treatment on chronotropic, inotropic responses of isolated rat heart tissue and relaxating responses of isolated rat aorta tissue to adrenaline were studied at the 24th, 48th, 72nd and 96th hours after the last medication. 47 rats were studied including 15 rats as a control group. Sudden withdrawal was found to cause a significant increase in chronotropic response to adrenaline at the 48th hour. But no effect on inotropic response on isolated rat heart tissue, and on the relaxation responses on isolated aorta tissue to adrenaline was shown. In conclusion, it was thought that treatment with and withdrawal of ICI-118, 551 does not cause a negative or restrictive effect on myocardial contractility and major vascular bed, but increased chronotropic response to endogenous adrenergic agonists at 48 hours following sudden withdrawal may occur.