Pharmacokinetic Interactions of a Licorice Dietary Supplement with Cytochrome P450 Enzymes in Female Participants

Licorice, the roots and rhizomes of Glycyrrhiza glabra L., has been used as a medicinal herb, herbal adjuvant, and flavoring agent since ancient times. Recently, licorice extracts have become popular as dietary supplements used by females to alleviate menopausal symptoms. Exposure to licorice products containing high levels of glycyrrhizic acid can cause hypokalemia, but independent from this effect, preclinical data indicate that licorice can inhibit certain cytochrome P450 (P450) enzymes. To evaluate whether clinically relevant pharmacokinetic interactions of licorice with P450 enzymes exist, a phase 1 clinical investigation was carried out using a licorice extract depleted in glycyrrhizic acid (content <1%) and a cocktail containing caffeine, tolbutamide, alprazolam, and dextromethorphan, which are probe substrates for the enzymes CYP1A2, CYP2C9, CYP3A4/5, and CYP2D6, respectively. The botanically authenticated and chemically standardized extract of roots from G. glabra was consumed by 14 healthy menopausal and postmenopausal female participants twice daily for 2 weeks. The pharmacokinetics of each probe drug were evaluated immediately before and after supplementation with the licorice extract. Comparison of the average areas under the time-concentration curves (AUCs) for each probe substrate in serum showed no significant changes from licorice consumption, whereas time to reach peak concentration for caffeine and elimination half-life for tolbutamide showed small changes. According to the US Food and Drug Administration guidance, which is based on changes in the AUC of each probe substrate drug, the investigated licorice extract should not cause any clinically relevant pharmacokinetic interactions with respect to CYP3A4/5, CYP2C9, CYP2D6, or CYP1A2. SIGNIFICANCE STATEMENT: Despite generally-recognized-as-safe status, the licorice species Glycyrrhiza glabra has been associated with some toxicity. Preclinical studies suggest that G. glabra might cause pharmacokinetic drug interactions by inhibiting several cytochrome P450 enzymes. This phase 1 clinical study addressed these concerns by evaluating clinically relevant effects with respect to CYP3A4/5, CYP2C9, CYP2D6, and CYP1A2. These results showed that a standardized G. glabra extract did not cause any clinically relevant pharmacokinetic drug interactions with four major cytochrome P450 enzymes.

No Clinically Relevant Pharmacokinetic Interactions of a Red Clover Dietary Supplement with Cytochrome P450 Enzymes in Women

Extracts of red clover (Trifolium pratense L.), containing estrogenic isoflavones like genistein and daidzein and the proestrogenic isoflavones formononetin and biochanin A, are used by women as dietary supplements for the management of menopausal symptoms. Although marketed as a safer alternative to hormone therapy, red clover isoflavones have been reported to inhibit some cytochrome P450 (CYP) enzymes involved in drug metabolism. To evaluate the potential for clinically relevant drug-red clover interactions, we tested a standardized red clover dietary supplement (120 mg isoflavones per day) for interactions with the pharmacokinetics of four FDA-approved drugs (caffeine, tolbutamide, dextromethorphan, and alprazolam) as probe substrates for the enzymes CYP1A2, CYP2C9, CYP2D6, and CYP3A4/5, respectively. Fifteen peri- and postmenopausal women completed pharmacokinetic studies at baseline and 2 weeks after consuming red clover. The averaged pharmacokinetic profiles of probe substrates in serum showed no significant alterations and no changes in the areas under the curve (AUC) over 96 h. Subgroup analysis based on the demographic characteristics (BMI, menopausal status, race, and age) also showed no differences in AUC for each probe substrate. Analysis of red clover isoflavones in serum showed primarily conjugated metabolites that explain, at least in part, the red clover pharmacokinetic safety profile.

Pharmacokinetic Interactions of a Hop Dietary Supplement with Drug Metabolism in Perimenopausal and Postmenopausal Women

Botanical dietary supplements produced from hops (Humulus lupulus) containing the chemopreventive compound xanthohumol and phytoestrogen 8-prenylnaringenin are used by women to manage menopausal symptoms. Because of the long half-lives of prenylated hop phenols and reports that they inhibit certain cytochrome P450 enzymes, a botanically authenticated and chemically standardized hop extract was tested for Phase I pharmacokinetic drug interactions. Sixteen peri- and postmenopausal women consumed the hop extract twice daily for 2 weeks, and the pharmacokinetics of tolbutamide, caffeine, dextromethorphan, and alprazolam were evaluated before and after supplementation as probe substrates for the enzymes CYP2C9, CYP1A2, CYP2D6, and CYP3A4/5, respectively. The observed area under the time-concentration curves were unaffected, except for alprazolam which decreased 7.6% (564.6 ± 46.1 h·μg/L pre-hop and 521.9 ± 36.1 h·μg/L post-hop; p-value 0.047), suggesting minor induction of CYP3A4/5. No enzyme inhibition was detected. According to FDA guidelines, this hop dietary supplement caused no clinically relevant pharmacokinetic interactions with respect to CYP2C9, CYP1A2, CYP2D6, or CYP3A4/5. The serum obtained after consumption of the hop extract was analyzed using ultra-high performance liquid chromatography-tandem mass spectrometry to confirm compliance. Abundant Phase II conjugates of the hop prenylated phenols were observed including monoglucuronides and monosulfates as well as previously unreported diglucuronides and sulfate-glucuronic acid diconjugates.

Stellate ganglion blockade and verbal memory in midlife women: Evidence from a randomized trial

OBJECTIVES

In a pilot randomized clinical trial of active stellate ganglion blockade (SGB) versus sham control, SGB significantly reduced the frequency of reported moderate to severe vasomotor symptoms (VMS) and the frequency of physiologic VMS measured using ambulatory skin conductance monitors. Here we examine secondary effects of SGB on verbal learning and memory.

STUDY DESIGN

In a randomized, sham-controlled study, 36 women met eligibility criteria for cognitive assessments, of whom 17 were randomized to receive fluoroscopy-guided SGB and 19 to sham control.

MAIN OUTCOME MEASURES

At baseline and three months post-treatment, women completed tests of verbal learning and memory (primary outcome) and other cognitive measures and also wore an ambulatory monitor for 24h to measure physiologic VMS and VMS reported in real time.

RESULTS

Verbal learning improved following active SGB (p<0.05) but not sham treatment; however, the interaction between group and time was not significant (p values 0.13-0.20). Two secondary cognitive measures improved only in the sham group. Improvements in physiologic VMS correlated significantly with improvements in verbal learning (r=0.51, p<0.05).

CONCLUSIONS

SGB might confer benefits to memory in relation to the magnitude of improvement in physiologic VMS. Broadly these findings suggest a possible link between physiologic VMS and memory problems in midlife women.

Pharmacokinetics of prenylated hop phenols in women following oral administration of a standardized extract of hops

SCOPE

Women seeking alternatives to hormone-replacement therapy for menopausal symptoms often try botanical dietary supplements containing extracts of hops (Humulus lupulus L.). Hops contain 8-prenylnaringenin (8-PN), a potent phytoestrogen, the related flavanones 6-prenylnaringenin and isoxanthohumol (IX), and the prenylated chalcone xanthohumol (XN).

METHODS AND RESULTS

After chemically and biologically standardizing an extract of spent hops to these marker compounds, an escalating dose study was carried out in menopausal women to evaluate safety and pharmacokinetics. 8-PN, 6-prenylnaringenin, IX, and XN, sex hormones, and prothrombin time were determined in blood samples and/or 24 h urine samples. There was no effect on sex hormones or blood clotting. The maximum serum concentrations of the prenylated phenols were dose-dependent and were reached from 2 to 7 h, indicating slow absorption. The marker compounds formed glucuronides that were found in serum and urine. Secondary peaks at 5 h in the serum concentration-time curves indicated enterohepatic recirculation. The serum concentration-time curves indicated demethylation of IX to form 8-PN and cyclization of XN to IX. Slow absorption and enterohepatic recirculation contributed to half-lives exceeding 20 h.

CONCLUSION

This human study indicated long half-lives of the estrogenic and proestrogenic prenylated phenols in hops but no acute toxicity.

Discussion of a well-designed clinical trial which did not demonstrate effectiveness: UIC center for botanical dietary supplements research study of black cohosh and red clover

The performance of a clinical trial for pharmaceutical agents is usually undertaken only after there is likely benefit demonstrated from the use of the putative agent. The consideration of botanical products as pharmaceutical agents must similarly go through a rigorous evaluation process. The present work reviews the recently published phase II study evaluating the effectiveness of black cohosh and red clover in a randomized trial with conjugated equine estradiol/medroxyprogesterone acetate and placebo for the treatment of menopausal symptoms. We analyze the possible reasons why this study failed to show benefit for either botanical product in reducing menopause-related vasomotor symptoms.

Effects of botanicals and combined hormone therapy on cognition in postmenopausal women

OBJECTIVE

The aim of this study was to characterize the effects of red clover, black cohosh, and combined hormone therapy on cognitive function in comparison to placebo in women with moderate to severe vasomotor symptoms.

METHODS

In a phase II randomized, double-blind, placebo-controlled study, 66 midlife women (of 89 from a parent study; mean age, 53 y) with 35 or more weekly hot flashes were randomized to receive red clover (120 mg), black cohosh (128 mg), 0.625 mg conjugated equine estrogens plus 2.5 mg medroxyprogesterone acetate (CEE/MPA), or placebo. Participants completed measures of verbal memory (primary outcome) and other cognitive measures (secondary outcomes) before and during the 12th treatment month. A subset of 19 women completed objective, physiological measures of hot flashes using ambulatory skin conductance monitors.

RESULTS

Neither of the botanical treatments had an impact on any cognitive measure. Compared with placebo, CEE/MPA led to a greater decline in verbal learning (one of five verbal memory measures). This effect just missed statistical significance (P = 0.057) in unadjusted analyses but reached significance (P = 0.02) after adjusting for vasomotor symptoms. Neither of the botanical treatment groups showed a change in verbal memory that differed from the placebo group (Ps > 0.28), even after controlling for improvements in hot flashes. In secondary outcomes, CEE/MPA led to a decrease in immediate digit recall and an improvement in letter fluency. Only CEE/MPA significantly reduced objective hot flashes.

CONCLUSIONS

Results indicate that a red clover (phytoestrogen) supplement or black cohosh has no effects on cognitive function. CEE/MPA reduces objective hot flashes but worsens some aspects of verbal memory.

Information preferences of high literacy pregnant women regarding informed consent models for genetic carrier screening

OBJECTIVE

With the increasing carrier screening options being offered to pregnant women, it is critical to consider what information women want in an informed consent process, and how they make decisions regarding screening.

METHODS

We surveyed 201 pregnant women.

RESULTS

Subjects prefer "to have as much information as possible" (84%), and valued their physician's recommendations (82%) regarding screening. After reviewing two hypothetical scenarios, 71% of participants preferred more information about genetic carrier screening; however, some participants expressed concern that too much information can also lead to anxiety. When specifically asked about components of a potential informed consent process, the highest preferences were to include: the chance of having a child with the disorder (97%), the options for carriers (93%), the value and purpose of testing (91%), and the prognosis if a child has the disease (94%); preference for "symptoms" information differed based on scenario preference (p<0.001).

CONCLUSION

This study is the first to document variation in patients' views regarding the information desired as part of the informed consent process.

PRACTICE IMPLICATIONS

Providers should consider ways to ascertain their patients' preferred informational style, and how to provide information in the amount and style that patients find useful in making decisions.

Clinical studies of red clover (Trifolium pratense) dietary supplements in menopause: a literature review

Red clover (Trifolium pratense L., Fabaceae) botanical dietary supplements have received much attention recently for their potential use in the treatment of menopause symptoms, maintenance/improvement of bone and cardiovascular health, and reported benign effects on the breast and endometrium. Literature searches of four computerized databases were run to identify clinical studies of red clover botanical dietary supplements. The manufacturer of the red clover products used in the majority of the studies was contacted for unpublished information and/or clarification regarding the chemical content of their products. Red clover studies were reviewed that pertained to women's health or menopause. Clinical evidence is presently lacking to support the efficacy of semipurified red clover isoflavone extracts for alleviation of climacteric vasomotor symptoms or reduction of low-density lipoprotein levels in the blood. Furthermore, the safety of use of red clover isoflavone supplements in patients with breast or endometrial cancer has not been established. Limited evidence suggests possible efficacy in maintenance of bone health and improvement of arterial compliance, a risk factor for atherosclerosis. This literature review covers red clover botanical dietary supplement clinical studies having a possible impact on the health care of mature and menopausal women, and provides historical perspective regarding the traditional uses of red clover.

What do patients prefer: informed consent models for genetic carrier testing

The recent increased number of conditions for which patients can undergo genetic carrier testing raises the question of how best to obtain pre-test informed consent. Clinical approaches vary from a minimalist model to a model where patients are given detailed information about all conditions to be screened for. Few data exist as to patient preferences, or how information impacts decision-making. Eight high-literacy focus groups were conducted to assess the knowledge and preferences of pregnant patients and their male partners. Most groups indicated that some balance between details and brevity was optimal, recognizing that anxiety can occur when patients are provided with too much information and that the wide range of tests offered during pregnancy often led to confusion. Critical areas for the informed consent process included (1) details about the conditions and risk of being a carrier, (2) logistics of testing, (3) next steps if the test is positive, and (4) prognosis, options and resources if the child were to be affected with a disorder. It will be useful to develop model consent programs and prospectively assess their impact on informed consent and patient satisfaction, both when positive and negative results are received.

Chemical and Biological Characterization and Clinical Evaluation of Botanical Dietary Supplements: A Phase I Red Clover Extract as a Model

Botanical dietary supplements, as compared with nutritional supplements or single-component pharmaceutical drugs, are typically less-refined preparations derived from bulk plant material and, as such, require a modified approach to their development, production, and evaluation. An integrated, multidisciplinary team of scientific and clinical investigators is required in order to develop high quality phytomedicines and rigorously evaluate their safety and efficacy. Research on botanicals involves unique challenges as plant source materials frequently vary in chemical content and may contain unwanted pesticides, heavy metals, contaminant plant species, or other adulterants. Ideally, a botanical formulation should be standardized, both chemically and biologically, by a combination of analytical techniques and bioassays. This combination approach provides multiple measures by which reproducible quality and efficacy of botanical supplements may be achieved, and is particularly useful for botanical products for which the active compound(s) have not yet been identified. Safety and toxicity should be evaluated during the supplement development process in both in vitro and in vivo systems. A number of liquid chromatography-mass spectrometry methods can aid in the assessment of purity, bioavailability, toxicity, metabolism, and molecular target profiling of botanical extracts. Clinical investigators must appreciate the complexity of multi-component phytomedicines and adjust trial protocols accordingly. This review highlights practical considerations of value to basic science and clinical investigators engaged in the study of botanical supplements. Lessons and examples are drawn from the authors' experience in designing and developing a red clover (Trifolium pratense L.) standardized extract for evaluation in Phase I and Phase II clinical trials.