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

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.

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.

A total of 24 women (mean age 27.3 years; mean body mass index 22.2 kg/m²) 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.

Co-administration of Silexan did not affect the efficacy of a combination oral contraceptive containing EE and LNG and was well tolerated.