Autonomic dysregulation and phenobarbital in patients with masked primary hypertension

INTRODUCTION: Primary hypertension can be masked and be responsible of a severe impact on the target bodies. The purpose of this study was to see if Phenobarbital at low dose is able to decrease the sympathetic hyperactivity assessed by cardiovascular autonomic reflexes in patients with masked hypertension. MATERIALS AND METHODS: This prospective study was conducted on a total of 91 patients with masked hypertension (average age 52.1 ± 10.3 years old). The cardiovascular autonomic tests performed in this group, before and after 3 months of daily oral administration of Phenobarbital, included deep breathing, hand-grip, mental stress and orthostatic tests. Statistical analysis was done using the Student's t-test, Univariate and Multivariate logistic regression analysis; p is significant if < 0.05. RESULTS: Cardiovascular autonomic reflexes responses before and after 3 months of Phenobarbital oral administration were as follows: Vagal response (XDB) obtained on deep breathing test was of 32.6 ± 5.4% VS 30.4 ± 6.1%, (p = 0.08), alpha peripheral sympathetic response (alpha SP) obtained on hand grip test was of 35.6 ± 8.7% VS 12.0 ± 2.5%, (p < 0.001), alpha central sympathetic response (alpha SC), beta central sympathetic response (beta SC) obtained during mental stress were of respectively 29.3 ± 9.2% VS 11.8 ± 2.4%, (p < 0.001) and 11.0 ± 5.3% VS 10.4 ± 6.1%, (p = 0.2), alpha peripheral adrenergic sympathetic (alpha PAS) obtained during orthostatic test was of 25.3 ± 6.0% VS 13.0 ± 3.4%, (p < 0.001). CONCLUSION: These results demonstrated that Phenobarbital at low dose may have an anti-sympathetic effect in patients with masked hypertension.