The effects of rilmenidine on cardiac autonomic function in healthy volunteers

Introduction and objectives. Rilmenidine is an antihypertensive drug whose anti hypertensive effect occurs via a sympatholytic action on the central nervous system. However, the effects of rilmenidine on autonomic cardiovascular function are not clear. The aim of this study was to evaluate the acute effect of rilmenidine on autonomic cardiac function by measuring heart rate variability. Subjects and method. A total of 20 healthy men (mean age, 26 3 years) were included in the study; 1 mg of rilmenidine or placebo was given to participants on different days in a double-blind crossover randomized study protocol. After drug administration, time domain and frequency domain parameters of heart rate variability were determined before and after 2 h with the patient in supine decubitus and during the handgrip exercise with 5-min electrocardiographic recordings. Results. Rilmenidine caused an increase in mean RR values after administration when compared to pre-drug administration recordings with the patient in supine decubitus (929 ms vs 860 ms, P<.05), but this effect was not found in the placebo group. However, there were no differences in other time domain parameters or in any of the frequency domain parameters (normalized low frequency unit, normalized high frequency unit and low frequency/high frequency ratio) with the participant in supine position in either group. In addition, neither rilmenidine nor placebo modified heart rate variability parameters during the handgrip exercise. Conclusion. Administration of a single dose of rilmenidine increased vagal tone without affecting vagal modulation in the supine position. The absence of vagal tone increase during the handgrip exercise suggests that this effect of rilmenidine is minimal.