Cerebral Bioavailability of Silexan—A Quantitative EEG Study in Healthy Volunteers

Background: A quantitative EEG (qEEG) study was performed to investigate the cerebral bioavailability of Silexan. Method: Twenty-four male and female healthy volunteers between 20 and 62 years of age were eligible for participation and received 160 or 80 mg/day Silexan or placebo in randomised order according to a 3-way crossover design. Treatment phases of 14 days were separated by 14-day washout periods. qEEG recordings in conditions “eyes open”, “eyes closed”, as well as during performance of 3 different cognitive tasks, were performed at 0, 1, 2, 3, and 4 h after drug administration on the first (single-dose assessment) and last day of each treatment period (repetitive dose assessment). Result: Compared with placebo, qEEG analysis revealed a significant increase of spectral power within two hours in the alpha1 range (7.0 9.5 Hz), particularly in the fronto-temporal region, where it was more pronounced after administration of Silexan 160 mg/day than after the 80 mg/day dose. Changes in other frequency bands were mainly attributable to circadian rhythm. No EEG changes typically seen during the investigation of sedative drugs (general theta increase) were observed. Cognitive task performance under both doses of Silexan was not inferior compared with that in the placebo period. Conclusions: The study provides evidence that ingredients of the anxiolytic lavender oil preparation Silexan penetrate the blood-brain barrier and induce functional changes in the CNS. The types of changes observed in the qEEG are consistent with the anxiolytic clinical effect of the drug represented by increases of alpha1 spectral power. No sedative effects were observed. Silexan was well tolerated during repetitive administration of doses up to twice the marketed dose.