Lavender, Lavandula angustifolia, ext.

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2013

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

2013

Materials and methods

Objective of study:

distribution

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

In a double-blind, randomized, 2-fold crossover study, 16 healthy male or female Caucasians were administered 160 mg silexan (contains 160 mg of an essential oil produced from Lavandula angustifolia) orally once daily for 11 days and the plasma samples were analysed for concentrations of Linalool and Linalyl Acetate. Further, potential effects of silexan on the activity of major P450s in humans were studied.

GLP compliance:

no

Test material

Test material information

Test material form:

not specified

Specific details on test material used for the study:

TEST MATERIAL
160 mg silexan (one soft gelatin capsule) preparation contains 160 mg of an essential oil produced from L. angustifolia flowers by steam distillation.

Radiolabelling:

no

Test animals

Species:

other: Human

Sex:

male/female

Administration / exposure

Route of administration:

other: oral

Vehicle:

unchanged (no vehicle)

Duration and frequency of treatment / exposure:

11 days

Doses / concentrations

Dose / conc.:

160 other: mg

No. of animals per sex per dose / concentration:

Sixteen healthy male or female Caucasians completed this double-blind, randomized, 2-fold crossover study.

Details on study design:

Study Population and Study Design:
The study protocol was approved by the Ethics Committee of the North Rhine Medical Association, Germany, and the study carried out in accordance with German laws, the Declaration of Helsinki, and other international guidelines. All study subjects provided written informed consent. Healthy male and female caucasians aged between 18 and 55 years were included in a single center, double-blind, randomized, placebo controlled, two-period crossover design.

Administration of Silexan (160 mg) or placebo:
- In the test period, 160 mg silexan (one soft gelatin capsule) was administered orally once daily on days 1–11. This preparation contains 160 mg of an essential oil produced from L. angustifolia flowers by steam distillation. In the reference period, placebo capsules were administered instead. For each drug intake, the volunteers reported to the study ward.

Drug Cocktail Interaction Study:
- In both study periods, administrations on day 11 were performed together with the five-probe phenotyping cocktail. The volunteers were hospitalized 12 h before cocktail administration until 24 h thereafter. Solid oral preparations of four cocktail drugs (150 mg caffeine, 125 mg tolbutamide, 20 mg omeprazole and 30 mg dextromethorphan-HBr) were administered orally together with silexan or placebo to evaluate the in vivo CYP1A2, 2C9, 2C19, and 2D6 activities, respectively.
- For the assessment of the total (liver and intestine) CYP3A4 activity, 2 mg midazolam were administered 1 minute thereafter. Intake of food and beverages was standardized for the in-house phase. On day 11, the fasting period lasted from at least 9 h before until 6 h after dosing, and fluid intake regularization was applied from 1 h before until 6 h after dosing. During the ambulant periods (days 1–10 in both study periods and the washout phase of 21 days between cocktail administrations), nonalcoholic and noncaffeinated food and beverages without quinine or grapefruit could be consumed ad libitum. Alcohol and grapefruit juice were prohibited from 1 week prior to the study until the follow up examination performed 4–10 days after last dosing.
- From 1 h before administration of phenotyping cocktail until 4 h post-dose, subjects remained in a recumbent position, which was continuously supervised by study personnel.
- The study subjects were closely surveyed throughout the study for evidence of clinical or laboratory adverse events (AEs).

Details on dosing and sampling:

Determination of constituents of silexan:
- Tissues and body fluids sampled: Blood
- Time and frequency of sampling: Blood (10 mL per sample) for the determination of constituents of silexan was sampled approximately 10 minutes prior to the 5th, 10th, and 11th dosing to quantify exposure.
- The blood samples were collected into Sarstedt Monovette citrate tubes (Sarstedt AG and Co., Nümbrecht, Germany) and then centrifuged (2000g, room temperature, 10 minutes). The resulting plasma was transferred into two polypropylene tubes, immediately frozen, and stored in a freezer at –20 °C or below until assayed.

Determination of the phenotyping substances
- For determination of the phenotyping substances and calculation of the primary phenotyping metrics, 9 mL blood samples were drawn approximately 10 minutes prior to dosing and 10, 20, 30, 45 minutes, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, 16, and 24 h post-dose. For determination of secondary phenotyping metrics with the purpose of further validation of the phenotyping results, additional blood sampling was carried out approximately 10 minutes prior to dosing and 3 and 6 h post-dose. The blood samples were collected into Sarstedt Monovette lithium heparin tubes, immediately cooled in ice water, and then centrifuged (2000g, +4 °C, 10 minutes). The supernatant plasma was transferred into four polypropylene tubes, immediately frozen, and stored deep-frozen at a temperature below –65 °C.

Analytical methods
Quantification of phenotyping substrates:
- The quantification of phenotyping substrates (caffeine, tolbutamide, omeprazole, dextromethorphan, and midazolam) in plasma was performed using specific and sensitive liquid chromatography/tandem mass spectrometry method.
Silexan constituents:
- For the silexan constituents linalool (3,7-dimethylocta-1,6-dien-3-ol) and linalyl acetate (3,7-dimethylocta-1,6-dien-3-yl acetate), samples were analyzed by headspace gas chromatography-mass spectrometry with electron ionization mode using a headspace autosampler G1888 (Agilent Technologies, Santa Clara, CA), gas chromatograph 7890A (Agilent Technologies; from 80 °C to 230 °C with 10 °C/min, helium, flow 1.5 mL/min), mass selective detector 5975C (Agilent Technologies), software MSDCHEM Station (Agilent Technologies), and a capillary column (J&W) DB WAXetr (60 m x 0.32 mm, 0.5 mm; Agilent Technologies). Dimethylsulfoxide was used as solvent for test and calibration solutions. Extraction and purification of reference substances was done in-house by Dr. Willmar Schwabe GmbH & Co. KG, Karlsruhe, Germany, achieving 97.6% purity of linalool and 97.7% purity for linalyl acetate. Quantification of both substances was performed by linear regression with the primary reference standard linalool (ion 93.1 m/z) and internal standard. Lower limit of quantification (LLOQ) for linalool and linalyl acetate was 2 ng/mL, working range was 2–2000 ng/mL.
- Interday precision for linalool was between 0.1 and 7.0% and for linalyl acetate between 0.4 and 12.0%, with interday accuracy between –6.0 and 1.6%, and –7.2 and 5.6%, respectively.

Statistics:

- Pharmacokinetic parameters of phenotyping drugs were determined from actual blood sampling times (relative to drug administration) for post-dose samples, and assayed drug plasma concentrations at these times using standard noncompartmental methods (WinNonlin Professional, version 5.2; Pharsight Corporation, Palo Alto, CA).
- Plasma concentrations and all phenotyping metrics were assumed to arise from a log-normal distribution (multiplicative model).
- For all probe substances of the cocktail, the main phenotyping metric was the area under the plasma concentration-time curve between administration and time of last quantifiable concentration (AUC0–t) of the parent compound. The treatments were compared using standard average bioequivalence procedures for the respective phenotyping metrics obtained following silexan (test) and placebo (reference) treatments. There was no adjustment for multiple comparisons because all assessments were considered as separate tests for the respective enzyme. Linear correlation was used to assess the relationship between primary and secondary phenotyping parameters.
- Sample Size Determination: Intraindividual CVs were assumed not to exceed 25% for any phenotyping metric. Lack of interaction was assumed if the 90% CI for estimated ratio µ test/µ reference did not exceed a tolerance zone of 0.70–1.43 for phenotyping metrics. For 0.95 ≤ true ratio µ test/µ reference ≤ 1.05, N = 14 would allow rejection of each null hypothesis “interaction present” with α = 0.05 (two-sided) and a power of at least 90%. Two additional subjects were included to account for eventual drop-outs as a safety margin, resulting in a sample size of N = 16.

Results and discussion

Main ADME results

Type:

distribution

Toxicokinetic / pharmacokinetic studies

Details on distribution in tissues:

Concentrations of Linalool and Linalyl Acetate in Plasma:
Following administration of silexan, concentrations of linalyl acetate were unquantifiably low (<2 ng/mL) in all samples, whereas the presence of linalool (concentrations ranged from 2.2 to 9.0 ng/mL, LLOQ 2 ng/mL) confirmed compliance in all cases. Mean values for the linalool concentrations were 2.02 ng/mL, 3.30 ng/mL, and 2.95 ng/mL prior to the 5th, 10th, and 11th dose of silexan, respectively, indicating that steady state has been reached on the phenotyping day.

Any other information on results incl. tables

Demographic data:

In total, 17 white Caucasian subjects (8 males, 9 females) participated in this study. The respective means and ranges for age and body mass index were 37 (21–52) years and 23.5 (19.7–26.9) kg/m². All subjects were nonsmokers at the time of the study, three subjects (17.6%) had smoked in the past. Six of the female subjects used oral contraceptives prior to and during the study. All subjects were healthy as confirmed by an extensive prestudy examination. After completion of the first study period, one subject withdrew due to AEs. Sixteen subjects completed the study and were included in the analysis.

 

Pharmacokinetic parameters for phenotyping substrates:

Mean C_max, AUC_0–t, and Area under the plasma concentration time curve extrapolated to infinity (AUC_0-∞) (reflecting the extent of drug absorption and exposure) as well as median t_max (indicating the rate of drug absorption) and mean t_1/2 (reflecting drug elimination) values of the probe substances were in most cases very similar after both treatments, with a few apparent exceptions. Median t_max of a CYP1A2 probe drug caffeine occurred later after silexan (0.76 h) than after placebo (0.55 h) administration. Mean AUC_0–t of the CYP2C19 probe substrate omeprazole was slightly increased after treatment with silexan (1164 h*nM) compared with the value observed after placebo treatment (1018 h*nM). For the CYP3A4 probe substrate midazolam, mean t_1/2 was shorter after silexan administration (3.53 h) compared with placebo administration (4.33 h).

 

Phenotyping metrics and effect of silexan on the activity of P450 enzymes:

For CYP1A2, 2C9, 2D6, and 3A4 metrics, the 90% CIs for the ratios (silexan/placebo) of the primary and secondary phenotyping metrics were well within the predefined acceptance range of 0.70–1.43. According to the _AUC0–t comparisons, silexan had no relevant effect on CYP1A2, 2C9, 2D6, and 3A4 activity. Secondary phenotyping metrics confirmed this result. Mean ratios for all omeprazole-derived metrics were close to unity. The 90% CI for the AUC_0–t ratio of omeprazole but not for omeprazole/5-OH-omeprazole plasma ratio 3 h post-dose or omeprazole/5-OH-omeprazole AUC_0–t ratio (secondary CYP2C19 metrics) was above the predefined threshold of 1.43, probably caused by the inherent high variability of omeprazole pharmacokinetics. Therefore, a clinically relevant pharmacokinetic interaction between silexan and CYP2C19 substrates is not expected.

Repeated silexan (160 mg/day) administration has no clinically relevant inhibitory or inducing effects on the CYP1A2, 2C9, 2C19, 2D6, and 3A4 enzymes in vivo.

 

Safety and tolerability:

Eleven adverse effects (AEs) were observed in 5/16 (31.3%) subjects and 30 AEs in 15/17 (88.2%) subjects during and until 7 days after last placebo or silexan administration.

Mild eructation occurred shortly after drug intake and was the most frequently reported AE, which was experienced by 10 (58.8%) subjects (in five subjects as a single event) after treatment with silexan and by no subject after placebo.

With respect to the double-blind treatment, the causal relationship with silexan was considered as probable for five AEs (five cases of eructation, silexan), as possible for eight AEs [eructation (five cases, silexan), diarrhea (one case, silexan), nausea (one case each, silexan and placebo)], and as unlikely for 27 AEs.

With respect to the phenotyping cocktail, the causal relationship was considered as possible for three AEs (nausea, dizziness, and vomiting) in two subjects and as unlikely for three AEs (cold, increased hematocrit, and increased erythrocytes count) in two subjects.

No severe or serious AEs occurred during the study. One subject dropped out due to moderate AEs (nausea before intake of study drug and vomiting after administration of the phenotyping cocktail) in the study period with silexan treatment.

Mean vital signs, ECG, and laboratory parameters showed no clinically relevant changes during the study.

Thus, repeated administration of silexan (160 mg/day) alone or together with the probe substrates were well tolerated by healthy subjects in this study.

Applicant's summary and conclusion

Conclusions:

Following administration of silexan, concentrations of linalyl acetate were unquantifiably low (<2 ng/mL). Mean values for the linalool concentrations were 2.02, 3.30 and 2.95 ng/mL prior to the 5th, 10th, and 11th dose of silexan, respectively, indicating that steady state has been reached on the phenotyping day.
Repeated silexan (160 mg/day) administration has no clinically relevant inhibitory or inducing effects on the CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4 enzymes either by indirect measurement of the pharmacokinetics of representative substances or by phenotyping metrics.

Executive summary:

In a double-blind, randomized, 2-fold crossover study, 16 healthy male or female Caucasians were administered 160 mg silexan (160 mg of an essential oil produced from Lavandula angustifolia) or placebo were administered once daily for 11 days. Additionally, on day 11 of both study periods, 150 mg caffeine (CYP1A2), 125 mg tolbutamide (CYP2C9), 20 mg omeprazole (CYP2C19), 30 mg dextromethorphan-HBr (CYP2D6), and 2 mg midazolam (CYP3A4) were administered orally. Plasma samples were analysed for concentrations of Linalool and Linalyl Acetate. Further, this cocktail study evaluated the interaction potential of the oral lavender oil preparation silexan with major P450 (cytochrome P450) enzymes.

Following administration of silexan, concentrations of linalyl acetate were unquantifiably low (<2 ng/mL) in all samples, whereas the presence of linalool (concentrations ranged from 2.2 to 9.0 ng/mL, LLOQ 2 ng/mL) confirmed compliance in all cases. Mean values for the linalool concentrations were 2.02 ng/mL, 3.30 ng/mL, and 2.95 ng/mL prior to the 5th, 10th, and 11th dose of silexan, respectively, indicating that steady state has been reached on the phenotyping day.

Silexan and the phenotyping drugs were well tolerated. Repeated silexan (160 mg/day) administration has no clinically relevant inhibitory or inducing effects on the CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4 enzymes either by indirect measurement of the pharmacokinetics of representative substances or by phenotyping metrics.