SPECIFICITY OF THE HYPOTENSIVE EFFECT OF CALCIUM-ANTAGONISTS IN PATIENTS WITH LOW-RENIN VARIANTS OF ESSENTIAL-HYPERTENSION
The purpose of the study was to define prognostic criteria that determine individual sensitivity to the hypotensive effect of slow calcium channel blockers. After two weeks of placebo therapy 45 patients suffering from essential hypertension underwent an acute pharmacological test (APT) with nifedipine in a dose of 30 mg. Then the patients received monotherapy with nitrendipine in the increasing doses for 12 weeks. The drug effect on the renin-angiotensin-aldosterone system and the level of ionized calcium in the blood serum was estimated. In 17 patients who responded to the APT by a decrease of the mean arterial pressure (MAP) by not less than 20%, arterial pressure was corrected with nitrendipine administered in a dose not exceeding 20 mg. 28 patients whose MAP dropped by 10 to 20 % in response to the APT required higher drug doses (40 mg). 7 patients in whom the MAP dropped less than 10 % were practically refractory to the monotherapy with nitrendipine. A close negative correlation was found between the degree of the MAP lowering in response to the APT during nitrendipine monotherapy and plasma renin activity as well as the concentration of ionized calcium in the blood serum. The low content (less than 1.0 mmol/l) of ionized calcium in the blood serum of patients suffering from essential hypertension appeared the most valuable predictor for the hypotensive effect of the slow calcium channel blockers.