No Interacting Influence of Lavender Oil Preparation Silexan on Oral Contraception Using an Ethinyl Estradiol/Levonorgestrel Combination

PURPOSE: Silexan is an oral Lavender oil preparation with proven anxiolytic efficacy. Given the high prevalence of anxiety and restlessness in younger women, oral contraceptives and Silexan will likely be co-administered. METHODS: A double-blind, randomised, 2-period crossover study was performed to investigate the effects of Silexan on the pharmacokinetics and pharmacodynamics of Microgynon(®), a combination oral contraceptive containing ethinyl estradiol 0.03 mg (EE) and levonorgestrel 0.15 mg (LNG) in healthy, fertile, adult females. During 2 consecutive cycles of 28 days, oral contraception was given for 21 days combined with 1 × 160 mg/day Silexan or placebo. Plasma concentration–time profiles of EE and LNG were obtained on day 18 ± 1 up to 24 h after dosing. The primary outcome measure was the area under the concentration–time curve over a dosing interval of τ = 24 h (AUCτ) for EE and LNG plasma levels. An interaction with Silexan was formally excluded if the 90 % confidence interval for the AUCτ ratio during co-administration with Silexan or placebo was included within the range of 0.80–1.25. Secondary outcomes included EE and LNG peak concentration (C (max)) and time to C (max) (t (max)), follicle size, endometrial thickness, the Hoogland score, and serum levels of estradiol, progesterone, and sex hormone-binding globulin. RESULTS: A total of 24 women (mean age 27.3 years; mean body mass index 22.2 kg/m(2)) participated. The confidence intervals for the EE and LNG AUCτ and C (max) ratios fell within the pre-specified limits, indicating no interaction (point estimates [Silexan/placebo] AUCτ EE 0.97, LNG 0.94; C (max) EE 0.99, LNG 0.96). For LNG, t (max) was slightly delayed. No secondary outcome indicated any impairment of contraceptive efficacy. CONCLUSIONS: Co-administration of Silexan did not affect the efficacy of a combination oral contraceptive containing EE and LNG and was well tolerated.