Short Communication MULTIPLE NIGHT-TIME DOSES OF VALERIAN (Valeriana officinalis) HAD MINIMAL EFFECTS ON CYP3A4 ACTIVITY AND NO EFFECT ON CYP2D6 ACTIVITY IN HEALTHY VOLUNTEERS

Valerian (Valeriana officinalis) is a popular dietary supplement. The objective of this study was to assess the influence of a valerian extract on the activity of the drug-metabolizing enzymes cytochrome P450 2D6 (CYP2D6) and 3A4. Probe drugs dextromethorphan (30 mg; CYP2D6 activity) and alprazolam (2 mg; CYP3A4 activity) were administered orally to healthy volunteers (n 12) at baseline and again after exposure to two 500-mg valerian tablets (1000 mg) nightly for 14 days. The valerian supplement contained a total valerenic acid content of 5.51 mg/tablet. Dextromethorphan to dextorphan metabolic ratios (DMRs) and alprazolam pharmacokinetics were determined at baseline and after valerian treatment. The DMR was 0.214 0.025 at baseline and 0.254 0.026 after valerian supplementation (p > 0.05). For alprazolam, the maximum concentration in plasma was significantly increased after treatment with valerian (25 7 ng/ml versus 31 8 ng/ml; p < 0.05). There were no significant differences in other pharmacokinetic parameters at baseline and after valerian exposure (all p values >0.05; time to reach maximum concentration in plasma, 3.0 3.2 versus 3.1 2.1 h; area under the plasma concentration versus time curve, 471 183 versus 539 240 h ng ml ; half-life of elimination, 13.5 4.3 versus 12.2 5.6 h). Our results indicate that although a modest increase was observed in the alprazolam Cmax, typical doses of valerian are unlikely to produce clinically significant effects on the disposition of medications dependent on the CYP2D6 or CYP3A4 pathways of metabolism. Valerian (Valeriana officinalis) extracts are marketed as dietary supplements in the United States and were among the top 10 bestselling herbal supplements in the United States in 2002 (Blumenthal, 2003). Although they are currently promoted as a sedative/hypnotic, clinical trials are presently inconclusive with regard to the efficacy for insomnia (Houghton, 1999; Stevinson and Ernst, 2000; Krystal and Ressler, 2001). Valerian supplements contain a complex mixture of chemical constituents (Shohet et al., 2001). The main constituents are valerenic acid and its derivatives contained in the volatile oil (Houghton, 1999). These main constituents are widely thought to contribute to the putative sedative effects, although clinical effects may be a result of synergistic activity from numerous constituents. The valepotriates have also been investigated for pharmacologic activity but are relatively unstable and are often not present in most commercial supplements (Bos et al., 2002). Minor constituents include various alkaloids, furanofuran lignans, and free amino acids (Houghton, 1999). Valerian is well recognized by its unpleasant odor that is attributed to isovaleric acid formation during processing and storage. The widespread use of valerian supplements suggests that use with conventional medications is inevitable, and the potential for drug interactions is undefined (Fugh-Berman and Ernst, 2001; Markowitz et al., 2003b; Huang et al., 2004). The present study was undertaken in healthy volunteers to determine whether a valerian supplement containing known quantities of valerenic acid and its derivatives could alter the activity of two major drug-metabolizing enzymes, cytochrome P450 2D6 (CYP2D6) and CYP3A4 in healthy volunteers. These two enzymes were chosen since, together, they contribute to the metabolism of a substantial number of both prescription and nonprescription medications (Wrighton and Thummel, 2000; Zanger and Eichelbaum, 2000; Burk and Wojnowski, 2004). To our knowledge, this is the first clinical study assessing whether a standardized valerian supplement may participate in drug interactions mediated by any of the P450 enzymes. Materials and Methods Subjects. The study was approved by the Medical University of South Carolina’s Office of Research Integrity, and subjects provided written informed consent before enrollment. Subjects were excluded if they had significant previous medical history or any current medical problems, or if they were taking any prescription or nonprescription medications, including oral contraceptives, herbal medications, or dietary supplements. Subjects were phenotyped with dextromethorphan (DM) before enrollment and excluded from the study if they were determined to be poor metabolizers for CYP2D6 using previously described criteria (Schmid et al., 1985). All subjects enrolled in the This study was made possible by Grant R21 AT00511 from the National Center for Complementary and Alternative Medicine. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the National Center for Complementary and Alternative Medicine, National Institutes of Health. Furthermore, the authors gratefully acknowledge Public Health Service Grant M01 RR01070-18 for the funding of the clinical study at the Medical University of South Carolina General Clinical Research Center. Article, publication date, and citation information can be found at http://dmd.aspetjournals.org. doi:10.1124/dmd.104.001164. ABBREVIATIONS: P450, cytochrome P450; ALPZ, alprazolam; AUC, area under the time versus concentration curve; Cmax, maximum concentration in plasma; DM, dextromethorphan; DMR, dextromethorphan to dextorphan metabolic ratio; Tmax, time to reach maximum concentration in plasma; GCRC, General Clinical Research Center. 0090-9556/04/3212-1333–1336$20.00 DRUG METABOLISM AND DISPOSITION Vol. 32, No. 12 Copyright © 2004 by The American Society for Pharmacology and Experimental Therapeutics 1164/1182116 DMD 32:1333–1336, 2004 Printed in U.S.A. 1333 at A PE T Jornals on Jauary 8, 2018 dm d.aspurnals.org D ow nladed from study were nonsmokers and were determined to be healthy by medical history, physical examination, basic laboratory monitoring indices, and 12-lead electrocardiogram. Subjects abstained from caffeine-containing beverages and ethanol use during the study period. Valerian Product. The valerian supplement used in this study was donated by Dr. Willmar Schwabe GmbH and Co. (Karlsruhe, Germany). This product had been prepared by extraction of valerian roots with 70% ethanol. Each tablet contained 500 mg of the dry valerian root extract derived from a single lot source. The content of valerenic acids was determined as described below before study initiation. Study Design and Drug Administration. This was an open-label, fixed treatment order, crossover study, with each subject serving as his or her own control. The clinical protocol has been extensively used in our laboratory to assess the effects of dietary supplements on P450 activity (Donovan et al., 2003, 2004; Markowitz et al., 2003a,b). Subjects were admitted to the Medical University of South Carolina’s General Clinical Research Center (GCRC) overnight and began the baseline P450 activity assessment the following morning. After an overnight fast and urinary void, each subject was administered a 30-mg oral dose of DM (Robitussin Maxium Strength cough syrup; Whitehall-Robins Healthcare, Madison, NJ) and 2 mg of alprazolam (ALPZ) (Mylan Pharmaceuticals, Inc., Morgantown, WV) with 30 to 60 ml of water. To eliminate any influence of food on the absorption of probe drugs, subjects did not eat breakfast but were fed a standard lunch 4 h after drug administration. An 8-h urine collection for the purpose of determining DM to dextrorphan metabolic ratios (DMRs) began immediately after probe drug administration, as well as collection of multiple blood samples for ALPZ analysis. Blood samples (10 ml) were obtained immediately before (0 h) and after the administration of ALPZ at 0.5, 1, 1.5, 2, 3, 4, 6, 8, 12, 24, 36, 48, and 60 h. Subjects were discharged from the GCRC at the 12-h time point and returned for outpatient visits for each of the final four blood draws. Heparinized 10-ml Vacutainer (BD Biosciences, Franklin Lakes, NJ) blood collection tubes were used for sampling. Collected blood samples were stored on ice until plasma separation, after which plasma was immediately stored at 70°C until analysis. After a minimum 7 day wash-out period, subjects were provided a 14-day supply of the valerian extract. The subjects were instructed to take two 500-mg tablets (1000 mg) nightly at bedtime between 9:00 PM and 12:00 AM. Valerian tablets were dispensed in preloaded medication organizers embossed with the days of the week (Mediset; Health Care Logistics Inc., Circleville, OH) in an effort to enhance subject compliance with dosing schedule and duration (Park et al., 1991). After 14 days of nightly exposure to 1000 mg of valerian extract, the subjects were readmitted to the GCRC for a second overnight stay. The following morning, subjects were administered 30 mg of DM and 2 mg of ALPZ as occurred in the baseline phase with identical specimen collection times. The preadmission nightly valerian dosing regimen continued for an additional 48 h during sample collection. Four hours after probe drug administration, each subject was served the same standard lunch they consumed during the baseline phase. Analytical Methods. DM, dextorphan, and ALPZ were determined using previously described high-performance liquid chromatography methods (Miller and DeVane, 1988; Hoskins et al., 1997). The pharmacokinetic software program WinNonlin (Pharsight, Mountain View, NC) was used to estimate ALPZ pharmacokinetics. Mean pharmacokinetic parameters, and the dextromethorphan to DMR at baseline and after valerian administration were analyzed using the paired t test. The level of significance was set at p 0.05. Laboratory analysis of the valerian supplement was undertaken before study initiation (ChromaDex Research and Development, Clearwater, FL). Analysis of tablets for valerenic acid, hydroxyvalerenic acid, and acetoxyvalerenic acid was performed using 10 tablets from the same lot used in the clinical study. The tablets were ground to a fine powder, and 1.6 g was dissolved in 60:40 acetonitrile/water. Samples were analyzed in duplicate using a Dionex Summit HPLC System (Dionex Corporation, Sunnyvale, CA). A linear gradient of 40 to 80% acetonitrile in an aqueous solution of 0.1% H3PO4 was performed over 20 min with a flow rate of 1.5 ml/min. The analytical column was a Luna C18 (2) 150 4.6 mm, 5m reversed phase column maintained at 25°C (Phenomenex, Torrance, CA). Detection was performed by UV absorption at 218 nm.