Dose and concentration-effect relations for rilmenidine.

The dose-effect and concentration-effect relations of rilmenidine, a new alpha 2 agonist, were evaluated for the hemodynamic and side-effect responses to single oral doses. Two studies were performed in a double-blind manner: study I in 8 healthy subjects and study II in 10 hypertensive patients. In the course of five 24-hour periods, each separated by at least 1 week, the following 5 treatments were administered in a random order: placebo, rilmenidine (0.5, 1, 2 and 3 mg). Blood pressure was measured with a Roche arteriosonde (study I) or a sphygmomanometer (study II). Sedation was measured using a visual analog scale. Dry mouth was assessed by measuring the salivary flow (study I) or by visual analog scale (study II). Plasma concentration of rilmenidine was assayed by gas chromatography linked with mass spectrometry. The antihypertensive and sedative effects (area under curve) were directly related to the dose and to the log of the plasma concentration of rilmenidine. In contrast to the 2- and 3-mg doses, rilmenidine (0.5 and 1 mg) did not induce orthostatic hypotension, a significant decrease in heart rate or a significant dryness of mouth. At doses of 0.5 and 1 mg, the effects of rilmenidine on sedation were not consistent in both studies: sedation was significant in study I but did not differ from placebo in study II. These studies show that rilmenidine, in common with other alpha 2 agonists, decreases blood pressure in a dose-dependent manner, in normotensive as well as in hypertensive subjects.(ABSTRACT TRUNCATED AT 250 WORDS)