RESUMEN
In 30 patients with mild hypertension (diastolic blood pressure, 95 to 105 mmHg), the antihypertensive effect of rilmenidine 1 mg was compared in a double-blind study, with the effect of hydrochlorothiazide 25 mg. Patients not satisfactorily controlled received a combined therapy on the same doses of the two drugs used. Rilmenidine and hydrochlorothiazide induced a significant reduction (p = 0.01) of supine and erect systolic/diastolic blood pressure 23 hours after drug intake with no change in heart rate. This effect was due to a reduction in cardiac output (bioimpedance method) significant (p = 0.05) only for rilmenidine. Both drugs controlled the increase of effort systolic blood pressure in comparison with placebo on systemic vascular resistance treadmill exercise testing. Effort cardiac output was increased by each treatment in comparison with baseline values. Both at rest and on exertion, there was no effect on systemic vascular resistance induced by the two drugs. In a second group of 10 patients with moderate hypertension (diastolic blood pressure, 105 to 115 mmHg), rilmenidine 1 mg was administered in order to evaluate its efficacy and hemodynamic effects (bioimpedance and radionuclide ventriculography), at rest and during a lying cycloergometer effort test. The drug induced a significant decrease in blood pressure at rest and on exertion four hours after drug intake. This effect was due to a reduction (p = 0.05) in systemic vascular resistance, whereas cardiac output and heart rate remained unchanged. Our results show that the reduction in systolic/diastolic blood pressure induced by rilmenidine 1 mg is comparable with that induced by the well-known antihypertensive drug hydrochlorothiazide in mild hypertension. In moderate hypertension, the 1-mg dose appears to be insufficient in controlling the blood pressure in all patients. The drug exerts its antihypertensive effect through the normalization of the altered hemodynamic parameters of hypertension (high cardiac output and/or increased systemic vascular resistance). Rilmenidine also respects the physiologic increase in blood pressure and cardiac output on exertion.