No relevant interaction with alprazolam, caffeine, tolbutamide, and digoxin by treatment with a low-hyperforin St John's wort extract

A Systematic Review and Classification of the Effects of P-glycoprotein Inhibitors and Inducers in Humans, Using Digoxin, Fexofenadine, and Dabigatran as Probe Drugs

P-glycoprotein is a critical efflux transporter that may significantly affect the pharmacokinetics of various drugs by influencing their absorption, distribution and elimination. While European and American regulatory guidelines provide lists of P-glycoprotein modulators, they lack specificity concerning in vivo studies and clear guidance on inducers, creating uncertainty in their clinical relevance. A systematic search on in vivo clinical studies involving healthy volunteers using fexofenadine, dabigatran and digoxin as P-glycoprotein substrates has been performed in accordance with the PRISMA guidelines. A total of 151 studies assessing the impact of P-glycoprotein modulators on the concentration-time profile of P-glycoprotein substrates were retrieved. Additionally, data on the P-glycoprotein modulators' effect on cytochrome P450 3A4 induction or inhibition were also collected. P-gp modulators were classified as potent, moderate, weak or non-interactors for P-glycoprotein, with or without cytochrome P450 3A4 impact, on the basis of the area under the concentration-time curve ratio. This classification was adapted from the Food and Drug Administration criteria for cytochrome interactions. This systematic review identified 49 area under the plasma concentration-time curve ratio values corresponding to P-glycoprotein inhibitors, 23 to P-glycoprotein inducers and 131 to non-interactors. Of these, only 32.5% and 41.1% were classified as weak to potent, respectively. Only 0.7% of inhibitors and no inducers were classified as potent. This suggests that most P-glycoprotein modulators have a limited impact on drug exposure. The potential for interaction increases when P-glycoprotein modulators also affect cytochrome P450 3A4, which is the case for 59.9% of P-glycoprotein modulators. However, some moderate P-glycoprotein modulators may have clinically significant effects depending on the therapeutic margin of the substrate and the clinical context.

Herb-drug interactions: A short review on central and peripheral nervous system drugs

Herbal medicines are widely perceived as natural and safe remedies. However, their concomitant use with prescribed drugs is a common practice, often undertaken without full awareness of the potential risks and frequently without medical supervision. This practice introduces a tangible risk of herb-drug interactions, which can manifest as a spectrum of consequences, ranging from acute, self-limited reactions to unpredictable and potentially lethal scenarios. This review offers a comprehensive overview of herb-drug interactions, with a specific focus on medications targeting the Central and Peripheral Nervous Systems. Our work draws upon a broad range of evidence, encompassing preclinical data, animal studies, and clinical case reports. We delve into the intricate pharmacodynamics and pharmacokinetics underpinning each interaction, elucidating the mechanisms through which these interactions occur. One pressing issue that emerges from this analysis is the need for updated guidelines and sustained pharmacovigilance efforts. The topic of herb-drug interactions often escapes the attention of both consumers and healthcare professionals. To ensure patient safety and informed decision-making, it is imperative that we address this knowledge gap and establish a framework for continued monitoring and education. In conclusion, the use of herbal remedies alongside conventional medications is a practice replete with potential hazards. This review not only underscores the real and significant risks associated with herb-drug interactions but also underscores the necessity for greater awareness, research, and vigilant oversight in this often-overlooked domain of healthcare.

Clinically Relevant Herb-Drug Interactions: A 30-Year Historical Assessment

The Dietary Supplement Health and Education Act, a legislative measure ushering in a novel class of complementary healthcare products known as dietary supplements, will mark its 30th anniversary in October 2024. Over this 30-year period, dietary supplement usage evolved from a few hundred products made up mostly of vitamins, minerals, and select botanical extracts to more than 75,000 single- and multi-ingredient products that are now regular staples in the American healthcare system and used by half of all U.S. consumers. One of the fastest-growing segments of the dietary supplement market during this 3-decade interval has been those products formulated with botanical extracts. Coincident with the growing popularity of botanical dietary supplements (BDS) has been their concomitant ingestion with conventional prescription medications. BDS are complex mixtures of phytochemicals oftentimes exhibiting complex pharmacology. Formulated as concentrated phytochemical extracts, BDS are vehicles for a host of plant secondary metabolites rarely encountered in the typical diet. When taken with prescription drugs, BDS may give rise to clinically significant herb-drug interactions (HDI). Pharmacodynamic HDI describe interactions between phytochemicals and conventional medications at the drug receptor level, while pharmacokinetic HDI stem from phytochemical-mediated induction and/or inhibition of human drug metabolizing enzymes and/or transporters. This review summarizes BDS identified over the last 30 years that pose clinically relevant HDI and whose mechanisms are either pharmacodynamically or pharmacokinetically mediated.

St. John's Wort Formulations Induce Rat CYP3A23-3A1 Independent of Their Hyperforin Content

The pregnane X receptor (PXR) is a ligand-activated regulator of cytochrome P450 (CYP)3A enzymes. Among the ligands of human PXR is hyperforin, a constituent of St John's wort (SJW) extracts and potent inducer of human CYP3A4. It was the aim of this study to compare the effect of hyperforin and SJW formulations controlled for its content on CYP3A23-3A1 in rats. Hyperiplant was used as it contains a high hyperforin content and Rebalance because it is controlled for a low hyperforin content. In silico analysis revealed a weak hyperforin-rPXR binding affinity, which was further supported in cell-based reporter gene assays showing no hyperforin-mediated reporter activation in presence of rPXR. However, cellular exposure to Hyperiplant and Rebalance transactivated the CYP3A reporter 3.8-fold and 2.8-fold, respectively, and they induced Cyp3a23-3a1 mRNA expression in rat hepatoma cells compared with control 48-fold and 18-fold, respectively. In Wistar rats treated for 10 days with 400 mg/kg of Hyperiplant, we observed 1.8 times the Cyp3a23-3a1 mRNA expression, a 2.6-fold higher CYP3A23-3A1 protein amount, and a 1.6-fold increase in activity compared with controls. For Rebalance we only observed a 1.8-fold hepatic increase of CYP3A23-3A1 protein compared with control animals. Even though there are differing effects on rCyp3a23-3a1/CYP3A23-3A1 in rat liver reflecting the hyperforin content of the SJW extracts, the modulation is most likely not linked to an interaction of hyperforin with rPXR. SIGNIFICANCE STATEMENT: Treatment with St John's wort (SJW) has been reported to affect CYP3A expression and activity in rats. Our comparative study further supports this finding but shows that the pregnane X receptor-ligand hyperforin is not the driving force for changes in rat CYP3A23-3A1 expression and function in vivo and in vitro. Importantly, CYP3A induction mimics findings in humans, but our results suggest that another so far unknown constituent of SJW is responsible for the expression- and function-modifying effects in rat liver.

Phytochemicals That Interfere With Drug Metabolism and Transport, Modifying Plasma Concentration in Humans and Animals

Phytochemicals (Pch) present in fruits, vegetables and other foods, are known to inhibit or induce drug metabolism and transport. An exhaustive search was performed in five databases covering from 2000 to 2021. Twenty-one compounds from plants were found to modulate CYP3A and/or P-gp activities and modified the pharmacokinetics and the therapeutic effect of 27 different drugs. Flavonols, flavanones, flavones, stilbenes, diferuloylmethanes, tannins, protoalkaloids, flavans, hyperforin and terpenes, reduce plasma concentration of cyclosporine, simvastatin, celiprolol, midazolam, saquinavir, buspirone, everolimus, nadolol, tamoxifen, alprazolam, verapamil, quazepam, digoxin, fexofenadine, theophylline, indinavir, clopidogrel. Anthocyanins, flavonols, flavones, flavanones, flavonoid glycosides, stilbenes, diferuloylmethanes, catechin, hyperforin, alkaloids, terpenes, tannins and protoalkaloids increase of plasma concentration of buspirone, losartan, diltiazem, felodipine, midazolam, cyclosporine, triazolam, verapamil, carbamazepine, diltiazem, aripiprazole, tamoxifen, doxorubicin, paclitaxel, nicardipine. Interactions between Pchs and drugs affect the gene expression and enzymatic activity of CYP3A and P-gp transporter, which has an impact on their bioavailability; such that co-administration of drugs with food, beverages and food supplements can cause a subtherapeutic effect or overdose. Therefore, it is important for the clinician to consider these interactions to obtain a better therapeutic effect.

The Challenge and Importance of Integrating Drug-Nutrient-Genome Interactions in Personalized Cardiovascular Healthcare

Despite the rich armamentarium of available drugs against different forms of cardiovascular disease (CVD), major challenges persist in their safe and effective use. These include high rates of adverse drug reactions, increased heterogeneity in patient responses, suboptimal drug efficacy, and in some cases limited compliance. Dietary elements (including food, beverages, and supplements) can modulate drug absorption, distribution, metabolism, excretion, and action, with significant implications for drug efficacy and safety. Genetic variation can further modulate the response to diet, to a drug, and to the interaction of the two. These interactions represent a largely unexplored territory that holds considerable promise in the field of personalized medicine in CVD. Herein, we highlight examples of clinically relevant drug–nutrient–genome interactions, map the challenges faced to date, and discuss their future perspectives in personalized cardiovascular healthcare in light of the rapid technological advances.

Pharmacokinetics of Caffeine: A Systematic Analysis of Reported Data for Application in Metabolic Phenotyping and Liver Function Testing

Caffeine is by far the most ubiquitous psychostimulant worldwide found in tea, coffee, cocoa, energy drinks, and many other beverages and food. Caffeine is almost exclusively metabolized in the liver by the cytochrome P-450 enzyme system to the main product paraxanthine and the additional products theobromine and theophylline. Besides its stimulating properties, two important applications of caffeine are metabolic phenotyping of cytochrome P450 1A2 (CYP1A2) and liver function testing. An open challenge in this context is to identify underlying causes of the large inter-individual variability in caffeine pharmacokinetics. Data is urgently needed to understand and quantify confounding factors such as lifestyle (e.g., smoking), the effects of drug-caffeine interactions (e.g., medication metabolized via CYP1A2), and the effect of disease. Here we report the first integrative and systematic analysis of data on caffeine pharmacokinetics from 141 publications and provide a comprehensive high-quality data set on the pharmacokinetics of caffeine, caffeine metabolites, and their metabolic ratios in human adults. The data set is enriched by meta-data on the characteristics of studied patient cohorts and subjects (e.g., age, body weight, smoking status, health status), the applied interventions (e.g., dosing, substance, route of application), measured pharmacokinetic time-courses, and pharmacokinetic parameters (e.g., clearance, half-life, area under the curve). We demonstrate via multiple applications how the data set can be used to solidify existing knowledge and gain new insights relevant for metabolic phenotyping and liver function testing based on caffeine. Specifically, we analyzed 1) the alteration of caffeine pharmacokinetics with smoking and use of oral contraceptives; 2) drug-drug interactions with caffeine as possible confounding factors of caffeine pharmacokinetics or source of adverse effects; 3) alteration of caffeine pharmacokinetics in disease; and 4) the applicability of caffeine as a salivary test substance by comparison of plasma and saliva data. In conclusion, our data set and analyses provide important resources which could enable more accurate caffeine-based metabolic phenotyping and liver function testing.

Clinical relevance of St. John's wort drug interactions revisited

The first clinically relevant reports of preparations of St. John's wort (SJW), a herbal medicine with anti‐depressant effects, interacting with other drugs, altering their bioavailability and efficacy, were published about 20 years ago. In 2000, a pharmacokinetic interaction between SJW and cyclosporine caused acute rejection in two heart transplant patients. Since then, subsequent research has shown that SJW altered the pharmacokinetics of drugs such as digoxin, tacrolimus, indinavir, warfarin, alprazolam, simvastatin, or oral contraceptives. These interactions were caused by pregnane‐X‐receptor (PXR) activation. Preparations of SJW are potent activators of PXR and hence inducers of cytochrome P450 enzymes (most importantly CYP3A4) and P‐glycoprotein. The degree of CYP3A4 induction correlates significantly with the hyperforin content in the preparation. Twenty years after the first occurrence of clinically relevant pharmacokinetic drug interactions with SJW, this review revisits the current knowledge of the mechanisms of action and on how pharmacokinetic drug interactions with SJW could be avoided.

Linked Articles

This article is part of a themed section on The Pharmacology of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.6/issuetoc

Pharmacokinetic Interactions between Cardiovascular Medicines and Plant Products

The growing use of plant products among patients with cardiovascular pharmacotherapy raises the concerns about their potential interactions with conventional cardiovascular medicines. Plant products can influence pharmacokinetics or/and pharmacological activity of coadministered drugs and some of these interactions may lead to unexpected clinical outcomes. Numerous studies and case reports showed various pharmacokinetic interactions that are characterized by a high degree of unpredictability. This review highlights the pharmacokinetic clinically relevant interactions between major conventional cardiovascular medicines and plant products with an emphasis on their putative mechanisms, drawbacks of herbal products use, and the perspectives for further well-designed studies.

No Clinically Relevant Interactions of St. John's Wort Extract Ze 117 Low in Hyperforin With Cytochrome P450 Enzymes and P-glycoprotein

Hypericum perforatum L. (St. John's wort) is used to treat mild-to-moderate depression. Its potential safety risks are pharmacokinetic drug interactions via cytochrome P450 (CYP) enzymes and P-glycoprotein, presumably caused by hyperforin. In a phase I, open-label, nonrandomized, single-sequence study, the low-hyperforin Hypericum extract Ze 117 was investigated using a drug cocktail in 20 healthy volunteers. No pharmacokinetic interactions of Ze 117 were observed for CYP1A2, CYP2B6, CYP2C9, CYP2C19, CYP3A4, and P-glycoprotein. Area under the curve (AUC) and peak plasma concentration (C_max ) of the used probe drugs showed 90% confidence intervals (CIs) of the geometric mean ratios of the drugs taken together with Ze 117 vs. probe drug alone, well within the predefined bioequivalence range of 80-125%. Though Ze 117 did not induce dextromethorphan metabolism by CYP2D6, it weakly increased dextromethorphan AUC ratio (mean 147.99, 95% CI 126.32-173.39) but not the corresponding metabolic ratio. Ze 117 does not show clinically relevant pharmacokinetic interactions with important CYPs and P-glycoprotein.

Interaction of herbal products with prescribed medications: A systematic review and meta-analysis

Although several studies on pharmacokinetic and/or pharmacodynamic herb-drug interactions (HDI) have been conducted in healthy volunteers, there is large uncertainty on the validity of these studies. A qualitative review and a meta-analysis were performed to establish the clinical evidence of these interaction studies. Out of 4026 screened abstracts, 32 studies were included into the qualitative analysis. The meta-analysis was performed on eleven additional studies. St. John's wort (SJW) significantly decreased the AUC (p < 0.0001) and clearance (p = 0.007) of midazolam. Further subgroup analysis identified age to affect C_max of midazolam (p < 0.01) in the presence of SJW. Echinacea purpurea (EP) significantly increased the clearance of midazolam (p = 0.01). Evidence of publication bias (p > 0.001) was shown on the effect of the herbal products o half-life of midazolam. Green tea (GT) showed significant 85% decrease in plasma concentration of nadolol. The study findings suggest that GT, SJW and EP perpetuate significant interactions with prescribed medications via CYP3A4 or OATP1A2. Our studies show that meta-analyses are important in the area of natural products to provide necessary information on their use in overall medication plans in order to avoid unintended interactions.

Interindividual Differences in Caffeine Metabolism and Factors Driving Caffeine Consumption

Most individuals adjust their caffeine intake according to the objective and subjective effects induced by the methylxanthine. However, to reach the desired effects, the quantity of caffeine consumed varies largely among individuals. It has been known for decades that the metabolism, clearance, and pharmacokinetics of caffeine is affected by many factors such as age, sex and hormones, liver disease, obesity, smoking, and diet. Caffeine also interacts with many medications. All these factors will be reviewed in the present document and discussed in light of the most recent data concerning the genetic variability affecting caffeine levels and effects at the pharmacokinetic and pharmacodynamic levels that both critically drive the level of caffeine consumption. The pharmacokinetics of caffeine are highly variable among individuals due to a polymorphism at the level of the CYP1A2 isoform of cytochrome P450, which metabolizes 95% of the caffeine ingested. Moreover there is a polymorphism at the level of another critical enzyme, N-acetyltransferase 2. At the pharmacodynamic level, there are several polymorphisms at the main brain target of caffeine, the adenosine A2A receptor or ADORA2. Genetic studies, including genome-wide association studies, identified several loci critically involved in caffeine consumption and its consequences on sleep, anxiety, and potentially in neurodegenerative and psychiatric diseases. We start reaching a better picture on how a multiplicity of biologic mechanisms seems to drive the levels of caffeine consumption, although much more knowledge is still required to understand caffeine consumption and effects on body functions.

Understanding drug interactions with St John's wort (Hypericum perforatum L.): impact of hyperforin content

Objective

The aim of this study was to review herb–drug interaction studies with St John's wort (Hypericum perforatum L.) with a focus on the hyperforin content of the extracts used in these studies.

Methods

PUBMED was systematically searched to identify studies describing pharmacokinetic interactions involving St John's wort. Data on study design and the St John's wort extract or product were gathered to extract hyperforin content and daily dose used in interaction studies.

Key findings

This analysis demonstrates that significant herb–drug interactions (resulting in a substantial change in systemic exposure) with St John's wort products were associated with hyperforin daily dosage. Products that had a daily dose of &lt;1 mg hyperforin were less likely to be associated with major interaction for drugs that were CYP3A4 or p-glycoprotein substrates. Although a risk of interactions cannot be excluded even for low-dose hyperforin St. John's wort extracts, the use of products that result in a dose of not more than 1 mg hyperforin per day is recommended to minimise the risk of interactions.

Conclusions

This review highlights that the significance of herb–drug interactions with St John's wort is influenced by the nature of the herbal medicines product, particularly the hyperforin content.

Therapeutic Risk and Benefits of Concomitantly Using Herbal Medicines and Conventional Medicines: From the Perspectives of Evidence Based on Randomized Controlled Trials and Clinical Risk Management

Despite increased awareness of the potential of herb-drug interactions (HDIs), the lack of rigorous clinical evidence regarding the significance provides a challenge for clinicians and consumers to make rational decisions about the safe combination of herbal and conventional medicines. This review addressed HDIs based on evidence from randomized controlled trials (RCTs). Literature was identified by performing a PubMed search till January 2017. Risk description and clinical risk management were described. Among 74 finally included RCTs, 17 RCTs (22.97%) simply addressed pharmacodynamic HDIs. Fifty-seven RCTs (77.03%) investigated pharmacokinetic HDIs and twenty-eight of them showed potential or actual clinical relevance. The extent of an HDI may be associated with the factors such as pharmacogenomics, dose of active ingredients in herbs, time course of interaction, characteristics of the object drugs (e.g., administration routes and pharmacokinetic profiles), modification of herbal prescription compositions, and coexistence of inducers and inhibitors. Clinical professionals should enhance risk management on HDIs such as increasing awareness of potential changes in therapeutic risk and benefits, inquiring patients about all currently used conventional medicines and herbal medicines and supplements, automatically detecting highly substantial significant HDI by computerized reminder system, selecting the alternatives, adjusting dose, reviewing the appropriateness of physician orders, educating patients to monitor for drug-interaction symptoms, and paying attention to follow-up visit and consultation.

Effects of Hypericum perforatum extract and its main bioactive compounds on the cytotoxicity and expression of CYP1A2 and CYP2D6 in hepatic cells

AIMS

Hypericum perforatum (H. perforatum) is one of the most used medicinal plants. However, it has been associated with relevant interactions with several drugs. This situation is probably mediated by cytochrome P450 enzymes (CYP450), namely the 1A2 (CYP1A2) and 2D6 (CYP2D6) isoforms This study aims to assess the cytotoxic and CYP1A2 and CYP2D6 inductive and/or inhibitory effects of a H. perforatum extract and its main bioactive components in hepatic cell lines.

MAIN METHODS

A MTT proliferation assay was performed in WRL-68, HepG2 and HepaRG cells after exposition to different concentrations of H. perforatum extract, hypericin and hyperforin for 24 and 72 h. Then, a real-time PCR analysis was accomplished after incubating the cells with these products evaluating the relative CYP1A2 and CYP2D6 expression.

KEY FINDINGS

These products have relevant cytotoxicity at a 10 μM concentration and it was also demonstrated for the first time that H. perforatum can lead to a significant CYP1A2 and CYP2D6 induction in all cell lines. Moreover, hypericin seems to induce CYP1A2 in HepG2 cells and to inhibit its expression in HepaRG cells while hyperforin induced CYP1A2 in HepG2 and in WRL-68 cells. Additionally, hypericin and hyperforin induce CYP2D6 in HepG2 cells but inhibits its expression in HepaRG and in WRL-68 cells.

SIGNIFICANCE

This study not only evidenced that H. perforatum extract and two of its bioactive components can have toxic effects in hepatic cell lines but also emphasized the potential risk of the consumption of H. perforatum with CYP1A2- and CYP2D6-metabolized drugs.

Influence of energy drink ingredients on mood and cognitive performance

Sales of energy products have grown enormously in recent years. Manufacturers claim that the products, in the form of drinks, shots, supplements, and gels, enhance physical and cognitive performance, while users believe the products promote concentration, alertness, and fun. Most of these products contain caffeine, a mild psychostimulant, as their foremost active ingredient. However, they also contain additional ingredients, e.g., carbohydrates, amino acids, herbal extracts, vitamins, and minerals, often in unspecified amounts and labeled as an "energy blend." It is not clear whether these additional ingredients provide any physical or cognitive enhancement beyond that provided by caffeine alone. This article reviews the available empirical data on the interactive effects of these ingredients and caffeine on sleep and cognitive performance and suggests objectives for future study.

Effects of notoginsenoside R1 on CYP1A2, CYP2C11, CYP2D1, and CYP3A1/2 activities in rats by cocktail probe drugs

CONTEXT

Notoginsenoside R1 (NGR1) is the main component with cardiovascular activity in Panax notoginseng (Burk.) F. H. Chen, an herbal medicine that is widely used to enhance blood circulation and dissipate blood stasis.

OBJECTIVE

The objective of this study is to investigate NGR1's effects on CYP1A2, CYP2C11, CYP2D1, and CYP3A1/2 activities in rats in vivo through the use of the Cytochrome P450 (CYP450) probe drugs.

MATERIALS AND METHODS

After pretreatment with NGR1 or physiological saline, the rats were administered intraperitoneally with a mixture solution of cocktail probe drugs containing caffeine (10 mg/kg), tolbutamide (15 mg/kg), metoprolol (20 mg/kg), and dapsone (10 mg/kg). The bloods were then collected at a set of time-points for the ultra-performance liquid chromatography/tandem mass spectrometry (UPLC-MS/MS) analysis.

RESULTS

NGR1 was shown to exhibit an inhibitory effect on CYP1A2 by increased caffeine Cmax (43.13%, p < 0.01) and AUC0 - ∞ (40.57%, p < 0.01), and decreased CL/F (62.16%, p < 0.01) in the NGR1-treated group compared with those of the control group, but no significant changes in pharmacokinetic parameters of tolbutamide, metoprolol, and dapsone were observed between the two groups, indicating that NGR1 had no effects on rat CYP2C11, CYP2D1, and CYP3A1/2.

DISCUSSION AND CONCLUSION

When NGR1 is co-administered with drugs that are metabolized by CYP1A2, the pertinent potential herb-drug interactions should be monitored.

Interactions between herbs and antidiabetics: an overview of the mechanisms, evidence, importance, and management

Complementary and alternative therapies are quickly gaining importance because they are perceived to be free of side effects due to their natural origin. However, herbal remedies are complex mixtures of bioactive entities, which may interact with prescription drugs through pharmacokinetic or pharmacodynamic mechanisms and sometimes result in life-threatening consequences. In particular, diabetes patients are often treated with multiple medications due to different comorbidities, and such patients use antidiabetic medications for their entire lives; thus, it is important to make the public aware of herb interactions with antidiabetic drugs. In this paper, we summarize the reports available on the interaction of herbal remedies with oral hypoglycemic agents and describe mechanisms, preclinical or clinical evidence, importance, and management strategies.

Interactions between herbs and conventional drugs: overview of the clinical data

This article provides an overview of the clinical evidence of interactions between herbal and conventional medicines. Herbs involved in drug interactions--or that have been evaluated in pharmacokinetic trials--are discussed in this review. While many of the interactions reported are of limited clinical significance and many herbal products (e.g. black cohosh, saw palmetto, echinacea, hawthorn and valerian) seem to expose patients to minor risk under conventional pharmacotherapy, a few herbs, notably St. John's wort, may provoke adverse events sufficiently serious to endanger the patients' health. Healthcare professionals should remain vigilant for potential interactions between herbal medicines and prescribed drugs, especially when drugs with a narrow therapeutic index are used.

Effect of Natural Products on Commercial Oral Antidiabetic Drugs in Enhancing 2-Deoxyglucose Uptake by 3T3-L1 Adipocytes

OBJECTIVE

The management of diabetes with insulin and synthetic oral hypoglycemic drugs (OHDs) can produce serious side effects and in addition fails to prevent diabetes-related complications in many patients. A new diabetes management strategy is needed that is more effective and has fewer side effects.

METHODS

This paper analyzes the dose- and time-dependent effect of three phytochemicals: berberine, arecoline and vanillic acid, and two antidiabetic drugs: 2,4-thiazolidinedione (TZD) and metformin, on the uptake of 2-deoxyglucose (2DG) by 3T3-L1 adipocytes. The interactions of the phytochemicals with the OHDs were analyzed with isobolograms and the combination index.

RESULTS

TZD and berberine increased 2DG uptake by 3.3-fold (with respect to control) at 15 μM and 25 μM, respectively. The same concentrations of arecoline and vanillic acid increased 2DG uptake by 3.2-and 2.9-fold, respectively, when compared with the basal level. Berberine and arecoline acted synergistically with both the OHDs, whereas vanillic acid had an additive interaction with TZD and an antagonistic interaction with metformin. Arecoline significantly increased the translocation of GLUT4 via the PPAR(γ) pathway, whereas berberine and vanillic acid did this via the AMPK-dependent pathway.

CONCLUSIONS

These phytochemicals significantly reduced the expression of the enzymes involved in fatty acid and cholesterol synthesis, indicating that they might help prevent the secondary complications of diabetes. The current study suggests that berberine and arecoline could allow dosage reduction of OHDs, which could also lead to a reduction in the toxicity and side effects caused by OHDs.

Pharmacokinetics and metabolism of natural methylxanthines in animal and man

Caffeine, theophylline, theobromine, and paraxanthine administered to animals and humans distribute in all body fluids and cross all biological membranes. They do not accumulate in organs or tissues and are extensively metabolized by the liver, with less than 2% of caffeine administered excreted unchanged in human urine. Dose-independent and dose-dependent pharmacokinetics of caffeine and other dimethylxanthines may be observed and explained by saturation of metabolic pathways and impaired elimination due to the immaturity of hepatic enzyme and liver diseases. While gender and menstrual cycle have little effect on their elimination, decreased clearance is seen in women using oral contraceptives and during pregnancy. Obesity, physical exercise, diseases, and particularly smoking and the interactions of drugs affect their elimination owing to either stimulation or inhibition of CYP1A2. Their metabolic pathways exhibit important quantitative and qualitative differences in animal species and man. Chronic ingestion or restriction of caffeine intake in man has a small effect on their disposition, but dietary constituents, including broccoli and herbal tea, as well as alcohol were shown to modify their plasma pharmacokinetics. Using molar ratios of metabolites in plasma and/or urine, phenotyping of various enzyme activities, such as cytochrome monooxygenases, N-acetylation, 8-hydroxylation, and xanthine oxidase, has become a valuable tool to identify polymorphisms and to understand individual variations and potential associations with health risks in epidemiological surveys.

[Pharmacokinetic drug interactions by herbal drugs: Critical evaluation and clinical relevance]

Pharmacokinetic herb-drug interactions are caused by an induction or inhibition of cytochrome P450 (CYP) enzymes or transporters e.g. P-glycoprotein. St. John's wort extracts containing hyperforin increase the expression of CYP-enzymes and P-glycoprotein mainly in the gut and liver which leads to a clinically relevant decrease of the bioavailability of CYP and P-glycoprotein substrates. Contrarily, the bioactivation of the prodrug losartan is reduced by milk thistle extracts which is due to an inhibition of CYP2C9. However, the 15 % reduction of the bioavailability of the active metabolite E-3174 is clinically not relevant. Also, minor changes in drug bioavailability observed in clinical studies for valerian, echinacea, ginkgo and hawthorne are clinically not relevant, although in vitro studies point to drug interactions in vivo. Since for herbal extracts a positive in vitro - in vivo correlation regarding the impact on drug bioavailability is rare, results from in vitro studies should be carefully interpreted.

Evaluation of in vivo P-glycoprotein phenotyping probes: a need for validation

Drug transporters are involved in clinically relevant drug-drug interactions. P-glycoprotein (P-gp) is an efflux transporter that displays genetic polymorphism. Phenotyping permits evaluation of real-time, in vivo P-gp activity and P-gp-mediated drug-drug interactions. Digoxin, fexofenadine, talinolol and quinidine are commonly used probe drugs for P-gp phenotyping. Although current regulatory guidance documents highlight methodologies for evaluating transporter-based drug-drug interactions, whether current probe drugs are suitable for phenotyping has not been established, and validation criteria are lacking. This review proposes validation criteria and evaluates P-gp probes to determine probe suitability. Based on these criteria, digoxin, fexofenadine, talinolol and quinidine have limitations to their use and are not recommended for P-gp phenotyping.

Drug-botanical interactions: a review of the laboratory, animal, and human data for 8 common botanicals

Many Americans use complementary and alternative medicine (CAM) to prevent or alleviate common illnesses, and these medicines are commonly used by individuals with cancer.These medicines or botanicals share the same metabolic and transport proteins, including cytochrome P450 enzymes (CYP), glucuronosyltransferases (UGTs), and P-glycoprotein (Pgp), with over-the-counter and prescription medicines increasing the likelihood of drug-botanical interactions.This review provides a brief description of the different proteins, such as CYPs, UGTs, and Pgp.The potential effects of drug-botanical interactions on the pharmacokinetics and pharmacodynamics of the drug or botanical and a summary of the more common models used to study drug metabolism are described.The remaining portion of this review summarizes the data extracted from several laboratory, animal, and clinical studies that describe the metabolism, transport, and potential interactions of 8 selected botanicals. The 8 botanicals include black cohosh, Echinacea, garlic, Gingko biloba, green tea, kava, milk thistle, and St John's wort; these botanicals are among some of the more common botanicals taken by individuals with cancer.These examples are included to demonstrate how to interpret the different studies and how to use these data to predict the likelihood of a clinically significant drug-botanical interaction.

Herb-drug interactions with St John's wort (Hypericum perforatum): an update on clinical observations

St John's wort (SJW) extracts, prepared from the aerial parts of Hypericum perforatum, contain numerous pharmacologically active ingredients, including naphthodianthrones (e.g., hypericin and its derivatives), phloroglucinols derivatives (e.g., hyperforin, which inhibits the reuptake of a number of neurotransmitters, including serotonin), and flavonoids. Such extracts are widely used for the treatment of mild-to-moderate depression. As a monotherapy, SJW has an encouraging safety profile. However, relevant and, in some case, life-threatening interactions have been reported, particularly with drugs which are substrate of cytochrome P450 and/or P-glycoprotein. Well-documented SJW interactions include (1) reduced blood cyclosporin concentration, as suggested by multiple case reports as well as by clinical trials, (2) serotonin syndrome or lethargy when SJW was given with serotonin reuptake inhibitors, (3) unwanted pregnancies in women while using oral contraceptives and SJW, and (4) reduced plasma drug concentration of antiretroviral (e.g., indinavir, nevirapine) and anticancer (i.e., irinotecan, imatinib) drugs. Hyperforin, which is believed to contribute to the antidepressant action of St John's wort, is also strongly suspected to be responsible of most of the described interactions.

Long-term effects of St. John's wort (Hypericum perforatum) treatment: a 1-year safety study in mild to moderate depression

Long-term safety and the effects of a St. John's wort (SJW) extract Ze 117 (Hypericum perforatum) were evaluated in the treatment of patients with depression. An open multicentre safety study with 440 out-patients suffering from mild to moderate depression according to ICD-10 was conducted. Patients were treated for up to 1 year with 500 mg St. John's wort extract per day (Ze 117). Evaluation criteria were safety (adverse event frequency) and influence on depression (HAM-D, CGI). Two hundred and seventeen (49%) patients reported 504 adverse events, 30 (6%) of which were possibly or probably related to the treatment. Gastrointestinal and skin complaints were the most common events associated with treatment. No age-related difference in the safety of the applied medication was found. The long-term intake of up to 1 year of the study medication did not result in any changes in clinical chemistry and electrocardiogram recordings. Body mass index (BMI) did not change either. Mean HAM-D scores decreased steadily from 20.58 at baseline to 12.07 at week 26 and to 11.18 at week 52. Mean CGI scores decreased from 3.99 to 2.20 at week 26 and 2.19 at week 52. Therefore, St. John's wort extract ZE 117 is a safe and effective way to treat mild to moderate depression over long periods of time, and therefore seems especially suitable for a relapse prevention.

Gauging the clinical significance of P-glycoprotein-mediated herb-drug interactions: comparative effects of St. John's wort, Echinacea, clarithromycin, and rifampin on digoxin pharmacokinetics

Concomitant administration of botanical supplements with drugs that are P-glycoprotein (P-gp) substrates may produce clinically significant herb-drug interactions. This study evaluated the effects of St. John's wort and Echinacea on the pharmacokinetics of digoxin, a recognized P-gp substrate. Eighteen healthy volunteers were randomly assigned to receive a standardized St. John's wort (300 mg three times daily) or Echinacea (267 mg three times daily) supplement for 14 days, followed by a 30-day washout period. Subjects were also randomized to receive rifampin (300 mg twice daily, 7 days) and clarithromycin (500 mg twice daily, 7 days) as positive controls for P-gp induction and inhibition, respectively. Digoxin (Lanoxin 0.25 mg) was administered orally before and after each supplementation and control period. Serial digoxin plasma concentrations were obtained over 24 h and analyzed by chemiluminescent immunoassay. Comparisons of area under the curve (AUC)((0-3)), AUC((0-24)), elimination half-life, and maximum serum concentration were used to assess the effects of St. John's wort, Echinacea, rifampin, and clarithromycin on digoxin disposition. St. John's wort and rifampin both produced significant reductions (p < 0.05) in AUC((0-3)), AUC((0-24)), and C(max), while clarithromycin increased these parameters significantly (p < 0.05). Echinacea supplementation did not affect digoxin pharmacokinetics. Clinically significant P-gp-mediated herb-drug interactions are more likely to occur with St. John's wort than with Echinacea.

Herbal supplements and therapeutic drug monitoring: focus on digoxin immunoassays and interactions with St. John's wort

Herbal supplements can affect concentrations of therapeutic drugs measured in biological fluids by different mechanisms. Herbal products can either directly interfere with the methodology used in the measurement of drugs or indirectly interfere by altering the pharmacokinetics of coadministered drugs. The active components of Chan Su, Lu-Shen-Wan, Dan Shen, Asian and Siberian ginseng, oleander containing supplements, and Ashwagandha interfere with digoxin measurements by immunoassays, especially the polyclonal antibody-based immunoassays. Herbal supplements are sometimes contaminated with Western drugs causing drug toxicity. A therapeutic drug monitoring (TDM) service is very helpful for diagnosis of drug toxicity in such patients. Herbal products such as St. John's wort, a popular herbal antidepressant, increase the clearance of certain drugs either by increasing the activity of liver or intestinal cytochrome P-450 mixed-function oxidase or through modulation of the P-glycoprotein efflux pump. Significantly reduced concentrations of various therapeutic drugs such as digoxin, theophylline, cyclosporine, tacrolimus, tricyclic antidepressants, warfarin, and protease inhibitors can be observed due to interaction of these drugs with St. John's wort, causing treatment failure. On the other hand, a few drugs such as carbamazepine, mycophenolic acid, and procainamide do not show any interaction with St. John's wort. Understanding the effect of herbal products on TDM methodologies and identification of interactions between herbal products and drugs by TDM are very important clinically.

Drug Treatment in Juvenile Depression - Is St. John's Wort a Safe and Effective Alternative?

Analyses of juvenile depression studies with long established anti-depressants (tricyclic anti-depressants) have revealed discouragingly little benefit, while side effects have been profound. Modern anti-depressants like selective serotonin reuptake inhibitors seemed to solve part of this problem until they were found to be associated with an increased risk of suicidal attempts and ideation, hostile behaviour and self-harm, while meta-analyses have revealed only marginal therapeutic effects for the majority. Actually, no drug is unequivocally accepted as the gold-standard for young depressive patients. St. John's Wort (SJW) has been traditionally used in Europe to treat symptoms associated with juvenile depression. Close to 50 clinical studies performed over the last two decades have been presented as evidence that standardized SJW preparations are equally effective as synthetic anti-depressants in the treatment of mild to moderate depression in adults. Tolerability is excellent, but some relevant drug interactions have to be considered. Today, SJW is by far the most frequently prescribed medication for child and adolescent depression in Germany. Some pilot and observational studies from Germany, Canada and the US have delivered promising results. However, randomised controlled trials amongst this age group have yet to be carried out and are long overdue.

Black cohosh with or without St. John's wort for symptom-specific climacteric treatment—Results of a large-scale, controlled, observational study

OBJECTIVES

To evaluate usage pattern, effectiveness and safety of Black cohosh alone or in fixed combination with St. John's wort on menopausal symptoms in general clinical practice.

METHOD

Prospective, controlled open-label observational study of 6141 women at 1287 outpatient gynecologists in Germany. Subjects were treated with recommended doses of study therapies, with treatment chosen by the participating physicians. Patients were followed up for 6 months, optionally 12 months. The primary effectiveness variable was Menopause Rating Scale (MRS) subscore PSYCHE at Month 3 evaluated by ANCOVA.

RESULTS

The treatment groups were comparable at baseline, excepting the main MRS score and the PSYCHE score (monotherapy: 0.31+/-0.22; combination therapy: 0.42+/-0.23). Reductions from baseline were seen with both regimens for all variables. The changes in the primary variable remained significantly different between groups (p<0.001) when adjusted for differences at baseline with the combination therapy being superior: from 0.37 (adjusted) to 0.25 (95% CI: 0.24-0.25) and 0.23 (95% CI: 0.22-0.23) at Month 3 in the monotherapy and combination-therapy groups, respectively. The improvement by both therapies was maintained at 6 and 12 months. The rate of possibly treatment-related adverse events was 0.16%, all non-serious.

CONCLUSION

The results support the effectiveness and tolerability profiles of two Black cohosh-based therapies for menopausal symptoms in general practice. They were used differentially: the monotherapy for neurovegetative symptoms, the combination for patients with more pronounced mood complaints. The fixed combination of Black cohosh and St. John's wort was superior to Black cohosh alone in alleviating climacteric mood symptoms.

Drug-herb interaction: effect of St John's wort on bioavailability and metabolism of procainamide in mice

CONTEXT

St John's wort induces the activity of the cytochrome P450 enzyme system causing treatment failure because of increased metabolism of many drugs. Procainamide is metabolized by a different pathway to N-acetyl procainamide.

OBJECTIVE

To study St John's wort-procainamide interaction using a mouse (Swiss Webster) model.

DESIGN

One group of mice (group A, 4 mice in each group) was fed St John's wort each day for 2 weeks (last dose 1 day before administration of procainamide); another group (group B) received the same dose of St John's wort for 1 week. The third group (group C) received only a single dose 1 hour before administration of procainamide, and the control group (group D) received no St John's wort. All groups later received a single oral dose of procainamide. Blood was drawn 1, 4, and 24 hours after administration of procainamide and concentrations in serum of procainamide as well as N-acetyl procainamide were measured using immunoassays.

RESULTS

The procainamide concentrations 1 hour after administration was highest in group C (mean, 11.59 microg/mL) followed by group A (9.92 microg/mL), whereas group B (7.44 microg/mL) and control group D (7.36 microg/mL) showed comparable values. The concentration in group C was significantly greater than the control group D (P = .03, 2-tailed independent t test). N-Acetyl procainamide concentrations and estimated half-life of procainamide among groups were comparable. In a separate experiment when mice were fed purified hypericin, the active component of St John's wort, a significant increase in bioavailability (53%) of procainamide was observed compared with the control group.

CONCLUSIONS

St John's wort has an acute effect to increase bioavailability of procainamide but has no effect on its metabolism.

Extract of Hypericum perforatum blocks caffeine-induced locomotor activity in mice: a possible role of nitric oxide

The present study investigated the effects of HPE on caffeine-induced locomotor activity in mice. Caffeine (4-16 mg/kg) or saline were given to adult male Swiss-Webster mice, and the locomotor activity was immediately measured for 30 min. HPE (6-48 mg/kg) and saline were injected to another group of mice and the locomotor activity was measured 20 min later. HPE (6-24 mg/kg) was also administered to another group of mice 20 min before caffeine (16 mg/kg) injections and the locomotor activity was recorded for 30 min immediately after caffeine administrations. Finally l-arginine (1 g/kg) was administered i.p. 20 min before HPE (6 mg/kg) and the locomotor activity was measured as mentioned above. Each group of mice was used only once. Caffeine produced some significant increases in locomotor activity of the mice. HPE (6-24 mg/kg) significantly blocked the caffeine-induced locomotor hyperactivity. Pretreatment of l-arginine (1 g/kg) reversed the inhibitory effect of HPE (6 mg/kg) on caffeine-induced locomotor activity without producing any significant effect on locomotor activity of the mice when it was administered alone. The results suggest that HPE blocks caffeine-induced locomotor hyperactivity in mice. Furthermore, the inhibitory effect of HPE on caffeine-induced locomotor activity may be related to its NOS inhibitory property.

Clinical risk management of herb-drug interactions

The concomitant use of conventional and herbal medicines can lead to clinically relevant herb-drug interactions. Clinical risk management offers a systematic approach to minimize the untoward consequences of these interactions by paying attention to: (i) risk identification and assessment; (ii) development and execution of risk reduction strategies; and (iii) evaluation of risk reduction strategies. This paper reviews which steps should be explored or taken in these domains to improve the clinical risk management of adverse herb-drug interactions.

Effects of St. John's wort supplementation on ibuprofen pharmacokinetics

BACKGROUND

St. John's wort is a popular herbal supplement that has been involved in various herb-drug interactions. Experimental findings suggest that the supplement may impact CYP2C9 metabolism. CYP2C9 is responsible for the irreversible metabolism of ibuprofen.

OBJECTIVE

To examine the effect of 3 weeks of St. John's wort administration on the stereoselective pharmacokinetics of ibuprofen.

METHODS

Eight male subjects participated in this study. The single-dose pharmacokinetics of ibuprofen were evaluated before and after 21 days of St. John's wort administration. Plasma ibuprofen concentrations were determined, using a stereoselective, reversed-phase HPLC assay. Model independent methods were used to evaluate the pharmacokinetics of each ibuprofen enantiomer. Data were analyzed by 2 way ANOVA testing and confidence interval testing.

RESULTS

S(+)-ibuprofen mean +/- SD AUC and maximum concentration (C(max)) values were 131.6 +/- 26.8 microg x h/mL and 31.8 +/- 7.33 microg/mL, respectively, for control samples and 122.4 +/- 32.9 microg x h/mL and 33.6 +/- 7.83 microg/mL, respectively, after St. John's wort treatment. R(-)-ibuprofen mean AUC and C(max) values were 85.1 +/- 26.6 microg x h/mL and 28.4 +/- 8.72 microg/mL, respectively, for control samples and 87.7 +/- 30.1 microg x h/mL and 30.0 +/- 8.97 microg/mL, respectively, for St. John's wort treatment samples. St. John's wort administration resulted in no significant effects on the C(max) and AUC of either stereoisomer. A 31% decrease in S(+)-ibuprofen mean residence time (p = 0.02) was observed.

CONCLUSIONS

St. John's wort administration for 21 days had no apparent clinically important impact on the single-dose pharmacokinetic parameters of S(+)- and R(-)-ibuprofen. Although St. John's wort treatment appears to significantly reduce the mean residence time of S-ibuprofen, no ibuprofen dose adjustments appear warranted when the drug is administered orally with St. John's wort, due to the lack of significant change observed in ibuprofen AUC and C(max) for either enantiomer.