Cardiovascular effects of melatonin in hypertensive patients well controlled by nifedipine: a 24-hour study

Aims As melatonin has been found to play a role in the mechanisms of cardio vascular regulation, we designed the present study to evaluate whether the evening ingestion of the pineal hormone might interfere with the antihypert ensive therapy in hypertensive patients well-controlled by nifedipine monot herapy. Methods Forty-seven mild to moderate essential hypertensive outpatients tak ing nifedipine GITS 30 or 60 mg monotherapy at 08.30 h for at least 3 month s, were given placebo or melatonin 5 mg at 22.30 h for 4 weeks according to a double-blind cross-over study. At the end of each treatment period patie nts underwent a 24 h noninvasive ambulatory blood pressure monitoring (ABPM ) during usual working days; sleeping period was scheduled to last from 23. 00 to 07.00 h. Results The evening administration of melatonin induced an increase of bloo d pressure and heart rate throughout the 24 h period (Delta SBP = + 6.5 mmH g, P< 0.001; Delta DBP = + 4.9 mmHg, P < 0.01; Delta HR = + 3.9 beats min ( -1), P< 0.01). The DBP as well as the HR increase were particularly evident during the morning and the afternoon hours. Conclusions We hypothesize that competition between melatonin and nifedipin e, is able to impair the antihypertensive efficacy of the calcium channel b locker. This suggests caution in uncontrolled use of melatonin in hypertens ive patients. As the pineal hormone might interfere with calcium channel bl ocker therapy, it cannot be considered simply a dietary supplement.