EFFECTS OF RILMENIDINE AND CLONIDINE ON THE ELECTROENCEPHALOGRAM, SACCADIC EYE-MOVEMENTS, AND PSYCHOMOTOR FUNCTION

Rilmenidine is a novel oxazoline derivative that is effective in the t reatment of hypertension. Studies in animals have indicated that rilme nidine may reduce blood pressure without the associated central alpha( 2) side effects of clonidine. The aim of this double-blind, crossover, placebo-controlled study was to evaluate the hypotensive and central sedative effects of single oral doses of rilmenidine (1 or 2 mg), clon idine (150 or 300 mu g), and lorazepam (2.5 mg) in 12 healthy male vol unteers. Drug effects were assessed with a test battery composed of re sting electroencephalogram, auditory evoked responses (AERs), saccadic eye movements. psychomotor performance, and subjective ratings as wel l as blood pressure and heart rate. Rilmenidine and clonidine produced similar dose-dependent reductions in blood pressure without an effect on heart rate. Saccadic eye movements were not significantly impaired after rilmenidine (1 mg) treatment in contrast to after clonidine (15 0 mu g) treatment. Peak saccadic velocity was impaired by all drugs ex cept rilmenidine (1 mg), which was indistinguishable from placebo. The electroencephalographic spectral analysis also demonstrated greater s edation with lorazepam than with the other drugs and greater vigilance with placebo and rilmenidine (1 mg) than with lorazepam. AERs showed a differentiation in sedative effects between lorazepam and clonidine (300 mu g) relative to placebo, rilmenidine (1 mg), and clonidine (150 mu g). These results are consistent with the hypothesis that at lower doses, rilmenidine may act preferentially through imidazoline recepto rs, whereas at higher doses, alpha(2)-adrenoceptors may became activat ed.