Abstract
The hemodynamic dose-response effects of intravenous (0.05 and 0.10 mg/kg) and oral (50 and 100 mg) atenolol were compared in a randomized between-group study of 24 men within seventeen hours of an acute uncompli cated myocardial infarction; 6 subjects were evaluated in each of the four groups. Hemodynamic variables were determined over a one-hour control per iod, following which the randomized dose of atenolol was administered and measurements repeated at 15 (intravenous therapy only), 30, 60, 90, 120, 180, 240, 300, and 360 minutes.
The peak hemodynamic effect was similar and independent of either the dosage or route of administration. In all groups atenolol reduced heart rate and cardiac and stroke volume indices. The pulmonary artery occluded pressure and systemic vascular resistance index were transiently increased. Mean arte rial pressure was significantly reduced only in the oral group with the highest pretreatment pressure. Maximum changes developed between fifteen and thirty minutes after intravenous dosing and between two and three hours after oral dosing. However, substantial reductions in cardiac index (-0.6 L/min/m2; p < 0.05) were already achieved at sixty minutes following oral dosing. The dura tion of pharmacodynamic activity was for two to three hours following intraven ous and for the study duration (four to six hours) after oral dosing. These data confirm the hemodynamic safety of atenolol after acute myocardial infarction.
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