Electrophysiological effects of intravenous rilmenidine in man

Ten patients (44 y), 6 with the Wolff-Parkinson-White syndrome, and none with hypertensive disease, underwent electrophysiological studies before and after intravenous infusion of a single dose of 1 mg rilmenidine administered over 15 min. The regimen produced a mean plasma rilmenidine concentration of 3.16 ng.ml-1 at the end of the infusion. There was no significant change in sinus cycle length, PR interval, QRS, QT duration or in PA, AH and HV intervals. Estimated sinoatrial conduction time and corrected sinus node recovery time did not significantly change. In one patient, however, an abnormal pause was noted after termination of rapid atrial pacing. The right atrial effective refractory period decreased from 209 to 194 ms. There was no significant change in the anterograde and retrograde block cycle length or in the refractoriness of the nodal, ventricular and accessory pathways. The cycle length of induced reciprocating tachycardia decreased slightly from 374 to 351 ms. No patient exhibited an abnormal response to the carotid sinus massage. The findings indicate that intravenous administration of 1 mg rilmenidine exerts modest effects on the electrophysiological parameters of the human heart.