Summary
Since vascular resistance is elevated in hypertension, it is suggested that vasodilators lower the blood pressure by a physiologic mechanism and therefore must be more useful than cardiac output-lowering drugs. This is not entirely correct. Drugs that lower cardiac output are also relative vasodilators, but the vasodilation occurs at a lower level of cardiac output. It is also not necessarily true that all vasodilators are good antihypertensive agents. The clinical profile of a vasodilator depends on its effect on the venous return, cardiac output, regional blood flow, renin-angiotensin system, and sympathetic reflexes. From the viewpoint of hemodynamics, an ideal antihypertensive drug is a vasodilator that does not excessively increase cardiac output, causes no fluid retention, does not induce a great deal of venodilation, and does not elicit substantial neurohumoral counterregulation. Angiotensin-converting-enzyme inhibitors, some calcium antagonists, and some combined alpha/beta-blocking agents come close to satisfying the hemodynamic definition of an ideal antihypertensive drug.
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Julius, S. Are different hemodynamic patterns of antihypertensive drugs clinically important?. Eur J Clin Pharmacol 38 (Suppl 2), S125–S128 (1990). https://doi.org/10.1007/BF01409481
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DOI: https://doi.org/10.1007/BF01409481