A study published in the British Journal of Clinical Pharmacology assessed the effects of cilnidipine on autonomic function, ambulatory BP and heart rate in patients with essential hypertension. Ten inpatients with mild to moderate essential hypertension (age 44-64 years) underwent a drug-free period for 7 days and a treatment period with cilnidipine 10 mg orally for another 7 days. On the sixth day of each period, patients were subjected to autonomic function tests (mental arithmetic test, a cold pressor test and a Valsalva manoeuvre). Following these tests, 24 h ambulatory BP, heart rate, and the electrocardiogram R-R intervals were monitored at 30 min intervals. A power spectral analysis of R-R intervals was performed to obtain the low-and high-frequency components. Cilnidipine was noted to significantly reduce 24 h BP by 6.5 +/- 1.7 mmHg systolic and 5.0 +/- 1.1 mmHg diastolic. During the cold pressor test, the maximum change in SBP and percentage changes in both systolic and diastolic BPs were significantly lower during the treatment period with cilnidipine as compared to the drug-free period. The baroreflex sensitivity, measured from the overshoot phase of the Valsalva manoeuvre, was not significantly different between the two periods. Cilnidipine was thus found to be effective as a once-daily antihypertensive agent and caused little influence on heart rate and the autonomic nervous system in patients with mild to moderate essential hypertension. Cilnidipine had an added benefit in the inhibition of the pressor response induced by acute cold stress.