Mechanism of antihypertensive action of dilevalol compared with that of "cardioselective" beta-blocking agents

The hemodynamic effects of dilevalol, a nonselective β-adrenergic blocking agent with vasodilating properties, were evaluated in 34 hypertensive patients and compared with those of the "cardioselective" β blockers atenolol and metoprolol in 21 patients. Hemodynamic measurements were obtained at baseline, after acute treatment (first dose) with dilevalol (400 mg) and atenolol (50 mg) or metoprolol (100 mg), and again after subchronic treatment with these agents. After both acute and subchronic treatment (mean daily dose 1,042 mg), dilevalol significantly reduced mean arterial pressure (MAP, p < 0.0001), by significantly reducing systemic vascular resistance index (SVRI, p < 0.001), and by not significantly altering cardiac index (CI). In contrast, atenolol and metoprolol significantly reduced MAP (p < 0.002) by significantly reducing CI (p < 0.0001), with a concomitant increase in SVRI (p < 0.007). Heart rate (HR) was reduced significantly less (p < 0.006) with dilevalol than with the cardioselective agents. Correlation of the decrease in MAP with other hemodynamic parameters revealed that the effects on MAP of acute treatment with the cardioselective drugs are related to a decrease in HR (r = 0.63, p = 0.002), whereas those of subchronic treatment are correlated to a decrease in CI (r = 0.59, p = 0.01). The decrease in MAP after acute and subchronic dilevalol treatment is correlated primarily with SVRI (r = 0.46 to 0.49, p < 0.01) and only secondarily with HR (r = 0.34, p < 0.05). Therefore, the main mechanism of antihypertensive action for dilevalol is vasodilation, in contrast to the cardioselective agents, which is β blockade.