Hemodynamic and vascular responses to antihypertensive treatment with adrenergic blocking agents: A review

Abstract

While the pharmacological effects of the three agents discussed (reserpine derivatives, guanethidine, and methyldopa) appear to depend upon interference with sympathetic nervous activity, they differ in their effects in man.After acute administration, there is a fall in blood pressure with each agent, but with reserpine and methyldopa, cardiac output is little affected. With methyldopa, the renal resistance appears to fall. Guanethidine produces a sharp fall in the cardiac output and renal blood flow.After treatment for a few days with these agents, the differences in their actions are less apparent, and from the very limited information available on long-term therapy, each of these agents achieves its hypotensive effect without reduction in cardiac output. The renal blood flow remains at control levels with reserpine and methyldopa but is still somewhat reduced with guanethidine.From the practical point of view, therefore, the decision to use one or another of these agents should rest upon differences in their clinical effectiveness and side effects. There is an urgent need for information on the changes in the action of these drugs during long-term therapy. These changes could be caused by the drugs' pharmacological effects or by physiological adaptations within the patient.