Rilmenidine is a novel oxazoline derivative that is effective in the treatment of
hypertension. Studies in animals have indicated that
rilmenidine 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),
clonidine (150 or 300 micrograms), and
lorazepam (2.5 mg) in 12 healthy male volunteers.
Drug effects were assessed with a test battery composed of resting electroencephalogram, auditory evoked responses (AERs), saccadic eye movements, psychomotor performance, and subjective ratings as well 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 (150 micrograms) treatment. Peak saccadic velocity was impaired by all drugs except
rilmenidine (1 mg), which was indistinguishable from placebo. The electroencephalographic spectral analysis also demonstrated greater sedation 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 micrograms) relative to placebo,
rilmenidine (1 mg), and
clonidine (150 micrograms). These results are consistent with the hypothesis that at lower doses,
rilmenidine may act preferentially through
imidazoline receptors, whereas at higher doses, alpha 2-adrenoceptors may become activated.