Benefits
Lower anxiety ratings in randomized trials
Five randomized, double-blind, placebo-controlled trials of Silexan 80 mg a day for 10 weeks, pooling 1,213 adults with a Hamilton Anxiety Scale score of 18 or more, found larger falls in anxiety scores than placebo. An independent meta-analysis put the average advantage at 2.9 points, while in three of these trials the placebo groups improved by 8.4 to 9.5 points on their own. All five trials were initiated by the manufacturer.
Sleep improves, but as a knock-on effect of reduced anxiety
In the 221-person trial that made the Pittsburgh Sleep Quality Index a co-primary outcome, Silexan 80 mg a day lowered scores by 5.5 points over 10 weeks against 3.8 on placebo. A mediation analysis of 212 participants from that trial found that 98.4 percent of the sleep improvement was explained by the fall in anxiety, with no measurable direct effect, so it is not a sedative sleep aid.
Mood ratings in trials of anxious and low mood
In 318 adults with mixed anxiety and depressive disorder, depression scores fell 9.2 points on Silexan 80 mg a day and 6.1 on placebo over 70 days. In 498 adults with mild or moderate major depression, the same dose beat placebo by 2.17 points over 8 weeks, with sertraline as a reference arm. Both trials were run with the manufacturer in diagnosed populations; this is not a treatment for depression.
Mechanism of action
Not a benzodiazepine-like effect in abuse testing
In laboratory work its investigators compared Silexan's calming profile with pregabalin. In a manufacturer-run five-way crossover study in 34 evaluable recreational users of sedative drugs, single 80 mg and 640 mg doses were rated like placebo for drug liking and caused no sedation, while lorazepam was clearly distinguished from both.
Voltage-gated calcium channel inhibition
In rodent tissue and cell work, lavender oil reduced calcium influx through N-type, P/Q-type and T-type voltage dependent calcium channels at nanomolar concentrations the authors relate to an 80 mg human dose, with the effect in the hippocampus carried mainly by the N-type and P/Q-type channels. This is laboratory and animal evidence for how the oil might work. It has not been shown in the brains of people taking capsules.
A possible serotonin-1A signal, seen on brain imaging
A PET imaging study gave 17 healthy men 160 mg/day of Silexan® or placebo for at least 8 weeks and found reduced serotonin-1A receptor binding potential in the temporal and fusiform gyri, hippocampus, insula and anterior cingulate cortex. The authors describe this as suggesting the serotonin-1A receptor is involved. It is a 17-person imaging study in healthy volunteers, it measured no symptom, and it does not establish partial agonism.
Clinical trials
Randomized, double-blind, multi-centre trial of Silexan 80 mg a day against lorazepam 0.5 mg a day for 6 weeks, with no placebo arm. (Woelk et al. 2010, Phytomedicine)
77 adults with generalized anxiety disorder.
Hamilton Anxiety Scale totals fell by 11.3 points on Silexan and 11.6 points on lorazepam, from a baseline of 25 in both groups. With no placebo group, the trial cannot separate either result from the placebo response, which was 8.4 to 9.5 points in three placebo-controlled Silexan trials. The authors reported no sedative effects with Silexan.
Randomized, double-blind, double-dummy trial in 539 adults meeting DSM-5 criteria for generalized anxiety disorder with a Hamilton Anxiety Scale score of 18 or more. Four arms for 10 weeks: Silexan 160 mg a day, Silexan 80 mg a day, paroxetine 20 mg a day as an active reference, and placebo. Two authors work for the manufacturer. (Kasper et al. 2014, Int J Neuropsychopharmacol)
539 adults with diagnosed generalized anxiety disorder.
Hamilton Anxiety Scale totals fell by 14.1 points on 160 mg, 12.8 points on 80 mg, 11.3 points on paroxetine and 9.5 points on placebo. Both Silexan® doses beat placebo (p < 0.01). The active reference, paroxetine, did not: it reached only p = 0.10 against placebo in the full analysis set, which is a real caution about how well this trial could tell treatments apart. Response rates were 51.9 percent on 80 mg and 37.8 percent on placebo. Adverse event rates on Silexan® were similar to placebo and lower than on paroxetine.