Potential metabolic interaction between St. John's wort and theophylline

Herb-Drug Interactions: Worlds Intersect with the Patient at the Center

This review examines three bodies of literature related to herb-drug interactions: case reports, clinical studies, evaluations found in six drug interaction checking resources. The aim of the study is to examine the congruity of resources and to assess the degree to which case reports signal for further study. A qualitative review of case reports seeks to determine needs and perspectives of case report authors. Methods: Systematic search of Medline identified clinical studies and case reports of interacting herb-drug combinations. Interacting herb-drug pairs were searched in six drug interaction resources. Case reports were analyzed qualitatively for completeness and to identify underlying themes. Results: Ninety-nine case-report documents detailed 107 cases. Sixty-five clinical studies evaluated 93 mechanisms of interaction relevant to herbs reported in case studies, involving 30 different herbal products; 52.7% of these investigations offered evidence supporting reported reactions. Cohen's kappa found no agreement between any interaction checker and case report corpus. Case reports often lacked full information. Need for further information, attitudes about herbs and herb use, and strategies to reduce risk from interaction were three primary themes in the case report corpus. Conclusions: Reliable herb-drug information is needed, including open and respectful discussion with patients.

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

Effect of Cellgevity® Supplement on Selected Rat Liver Cytochrome P450 Enzyme Activity and Pharmacokinetic Parameters of Carbamazepine

BACKGROUND

There is considerable evidence that many patients concurrently administer dietary supplements with conventional drugs, creating a risk for potential drug-supplement interaction. The aim of this study was to determine the effect of Cellgevity® supplement on selected rat liver cytochrome P450 (CYP) enzymes. Also, based on our previous finding, we sought to determine the effect of Cellgevity® on the pharmacokinetics of carbamazepine, a CYP3A4 substrate.

METHODS

Male Sprague-Dawley (SD) rats were randomly put into 5 groups and administered either distilled water (negative control), Cellgevity® (3 separate doses), or phenobarbital (positive control), per os. Modulation of liver CYP enzyme activity was evaluated after 30 days of treatment, using probe substrates, spectroscopic, and high-performance liquid chromatographic methods. In the pharmacokinetic study, 12 SD rats were put into 2 groups and administered carbamazepine plus normal saline (group 1) or carbamazepine plus Cellgevity® (group 2), per os, both over a period of 14 days. Blood samples from rats in the same group were collected after treatment. Serum samples were prepared and pooled together at each specific sampling time point. Levels of carbamazepine were determined using a fluorescence polarization immunoassay.

RESULTS

Activities of rat liver CYP1A1/2, CYP2C9, and CYP2D6 were significantly increased by Cellgevity® after 30-day treatment. Pharmacokinetic parameters for rats administered carbamazepine with Cellgevity® vis-a-vis carbamazepine with normal saline were as follows: C _max; 20 μmol/L vs 11 μmol/L, AUC_0⟶24; 347 μmol h/L vs 170 μmol h/L, K _e; 0.28 h^-1 vs 0.41 h^-1, and t _1/2; 2.3 h vs 1.7 h, respectively.

CONCLUSIONS

Cellgevity® increased the activity of rat CYP1A1/2, CYP2C9, and CYP2D6 enzymes and was found to alter the pharmacokinetics of carbamazepine in rats.

Pharmacokinetic Herb-Drug Interactions: Insight into Mechanisms and Consequences

Herbal medicines are currently in high demand, and their popularity is steadily increasing. Because of their perceived effectiveness, fewer side effects and relatively low cost, they are being used for the management of numerous medical conditions. However, they are capable of affecting the pharmacokinetics and pharmacodynamics of coadministered conventional drugs. These interactions are particularly of clinically relevance when metabolizing enzymes and xenobiotic transporters, which are responsible for the fate of many drugs, are induced or inhibited, sometimes resulting in unexpected outcomes. This article discusses the general use of herbal medicines in the management of several ailments, their concurrent use with conventional therapy, mechanisms underlying herb-drug interactions (HDIs) as well as the drawbacks of herbal remedy use. The authors also suggest means of surveillance and safety monitoring of herbal medicines. Contrary to popular belief that "herbal medicines are totally safe," we are of the view that they are capable of causing significant toxic effects and altered pharmaceutical outcomes when coadministered with conventional medicines. Due to the paucity of information as well as sometimes conflicting reports on HDIs, much more research in this field is needed. The authors further suggest the need to standardize and better regulate herbal medicines in order to ensure their safety and efficacy when used alone or in combination with conventional drugs.

St John's Wort: A Hidden Risk for Transplant Patients

Herbal medications may cause prescription drug interactions in transplant recipients. After 2 of our kidney transplant recipients started self-medicating with St John's wort, their cyclosporine concentrations were consistently documented to be subtherapeutic. While on St John's wort, one patient developed acute rejection possibly due to low cyclosporine concentrations. Termination of St John's wort returned both patients' cyclosporine concentrations to therapeutic values. Based on the Naranjo Adverse Drug Reaction Probability Scale, our report would achieve a “probable” score, which supports the existence of a St John's wort–cyclosporine adverse drug interaction. St John's wort may induce cytochrome P-450 3A4 activity and/or P-glycoprotein expression, which are both involved in the metabolism and absorption of cyclosporine. Patients using St John's wort concomitantly with cyclosporine or other medications with similar absorption and/or metabolism to cyclosporine need close monitoring. Transplant coordinators are in a critical position to educate transplant recipients about the potential risks of herbal medication usage.

Clinical Corner: Herb-Drug Interactions in Cancer Chemotherapy: Theoretical Concerns Regarding Drug Metabolizing Enzymes

Interactions between herbal medicines and conventional drugs have recently been reported; the most significant herb with such drug interactions is Saint John's wort, an inducer of cytochrome P450 3A3/4, an enzyme responsible for clearance of many clinically important drugs from the body. Foods (especially grapefruit) and habits or lifestyle factors such as smoking or alcohol consumption may also alter the metabolism of drugs through effects on the cytochrome P450 system. The authors review here the functioning of the drug-metabolizing enzymes and discuss their particular sig nificance in cancer chemotherapy treatment. They then present the herbal medicines, foods, and lifestyle factors that induce or inhibit drug-metabolizing enzymes that are important for both cancer chemotherapy drugs and drugs used adjunctively in cancer treatment. It is notable that no actual herb-drug interactions have been reported clinically in cancer treatment, and their potential for interaction still must be regarded as theoretical. Although some chemotherapy patients may be interested in taking herbal medicines that could potentially interact with cancer chemotherapy agents, it may be wise to counsel them to use other means of addressing the problems for which they use specific herbs during the time they receive chemotherapy.

Antidepressant Drug Interactions

Second-generation antidepressants are more selective in their pharmacological mechanisms and offer fewer side effects and a safer toxicological profile than cyclic antidepressants and monoamine oxidase inhibitors. While the risk for pharmacodynamic interactions is more limited than with older agents with broader receptor effects, the risks for pharmacokinetic interactions is greater. The capacity of selective serotonin reuptake inhibitors to inhibit the metabolic activity of cytochrome P450 isozyme system has spurred over a decade of intense psychopharmacological and pharmacogenetics research to better the understanding of the significance of these interactions. Clinicians have had to increase their knowledge and understanding of drug interaction potential to better manage patients receiving these newer antidepressants. The following is a review of both pharmacodynamic and pharmacokinetic drug-drug interactions with antidepressants.

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.

Ophiopogon japonicus strains from different cultivation regions exhibit markedly different properties on cytotoxicity, pregnane X receptor activation and cytochrome P450 3A4 induction

Maidong, known as Ophiopogon japonicus, is one of the two basic ingredients of Shenmai injection, which is a widely used herbal preparation in traditional Chinese medicine (TCM) for the treatment of atherosclerotic coronary heart disease and viral myocarditis. Previously, the ethanol extract of Maidong activated the pregnane X receptor (PXR) signaling pathway and induced the cytochrome P450 3A4 (CYP3A4) reporter gene and raised the concern of herb-drug interactions (HDIs) when Maidong was used in combination with prescribed drugs metabolized by CYP3A4. Therefore, the present study further investigated and compared the differences of the ethanol and aqueous extracts (ee- and ae-, respectively) of two Maidong strains, known as Zhe Maidong (ZM) and Chuan Maidong (CM). Cytotoxicity, PXR activation and CYP3A4 induction by the 3-(4,5)-dimethylthiahiazo-(-z-y1)-3,5-diphenytetrazoliumromide assay, reporter gene assay and reverse transcription-quantitative polymerase chain reaction analysis were examined. The observations showed that ee-ZM demonstrated a significantly higher cytotoxicity, a relatively weaker PXR activation capability and a markedly stronger CYP3A4-inducing capacity than ee-CM. Compared to ae-CM, ae-ZM exhibited only a slight or no difference on cytotoxicity and CYP3A4 induction, while a significant lower level of PXR activation was apparent. Collectively, Maidong from different producing areas possess different properties upon cytotoxicity and the drug-metabolizing enzyme inducing effect, and attention should be paid to the selection of Maidong strains from different planting regions into TCM preparations for reducing potential adverse reactions and HDIs.

Hypericum perforatum: pharmacokinetic, mechanism of action, tolerability, and clinical drug-drug interactions

Hypericum perforatum (HP) belongs to the Hypericaceae family and is one of the oldest used and most extensively investigated medicinal herbs. The medicinal form comprises the leaves and flowering tops of which the primary ingredients of interest are naphthodianthrones, xanthones, flavonoids, phloroglucinols (e.g. hyperforin), and hypericin. Although several constituents elicit pharmacological effects that are consistent with HP's antidepressant activity, no single mechanism of action underlying these effects has thus far been found. Various clinical trials have shown that HP has a comparable antidepressant efficacy as some currently used antidepressant drugs in the treatment of mild/moderate depression. Interestingly, low-hyperforin-content preparations are effective in the treatment of depression. Moreover, HP is also used to treat certain forms of anxiety. However, HP can induce various cytochrome P450s isozymes and/or P-glycoprotein, of which many drugs are substrates and which are the main origin of HP-drug interactions. Here, we analyse the existing evidence describing the clinical consequence of HP-drug interactions. Although some of the reported interactions are based on findings from in vitro studies, the clinical importance of which remain to be demonstrated, others are based on case reports where causality can, in some cases, be determined to reveal clinically significant interactions that suggest caution, consideration, and disclosure of potential interactions prior to informed use of HP.

The Influence of St. John's Wort on CYP2C19 Activity with Respect to Genotype

Induction of cytochrome p450 isozymes is the major cause for clinical drug interactions of St. John's wort. The relationships of St. John's wort to cytochrome p450 isoforms have been fully investigated, but its effect on CYP2C19 is lacking. Thus, the aim of the present study was to observe the effect of St. John's wort on CYP2C19 activity using CYP1A2 as a control. Twelve healthy adult men-6 extensive metabolizers of CYP2C19 (2C19(*)1/2C19(*)1) and 6 poor metabolizers (4 2C19(*)2/2C19(*)2 and 2 2C19(*)2/2C19(*)3)-were enrolled in a two-phase, randomized, crossover manner. All subjects took a 300-mg St. John's wort tablet or placebo three times daily for 14 days, and then the activities of CYP2C19 and CYP1A2 were measured using mephenytoin and caffeine. It was found that St. John's wort treatment significantly increased CYP2C19 activity in CYP2C19 wild-genotype subjects, with urinary 4'-hydroxymephenytoin excretion raised by 151.5% +/- 91.9% (p = 0.0156), whereas no significant alteration was observed for CYP2C19 poor metabolizers. Repeated St. John's wort administration did not affect the CYP1A2 phenotypic ratio for both CYP2C19 genotype subjects. In conclusion, St. John's wort is an inducer to the human CYP2C19, and clinicians should pay great attention when St. John's wort is added to or withdrawn from an existing drug regimen containing substrates for such enzymes.

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.

Herbal remedies, mood, and cognition

Herbal medicines were the "sole" source of medicine for thousands of years, in every culture since the advent of human civilization. Today, patients are increasing the use of these botanicals for numerous conditions, such as mood and cognition. This article will explore commonly used herbal remedies for mood and cognition functioning. It is imperative that nurses and nurse practitioners obtain expertise with these botanicals with regard to efficacy, adverse effects and contraindications, possible drug interactions, and safety considerations.

Novel natural inhibitors of CYP1A2 identified by in silico and in vitro screening

Inhibition of cytochrome P450 (CYP) is a major cause of herb–drug interactions. The CYP1A2 enzyme plays a major role in the metabolism of drugs in humans. Its broad substrate specificity, as well as its inhibition by a vast array of structurally diverse herbal active ingredients, has indicated the possibility of metabolic herb–drug interactions. Therefore nowadays searching inhibitors for CYP1A2 from herbal medicines are drawing much more attention by biological, chemical and pharmological scientists. In our work, a pharmacophore model as well as the docking technology is proposed to screen inhibitors from herbal ingredients data. Firstly different pharmaphore models were constructed and then validated and modified by 202 herbal ingredients. Secondly the best pharmaphore model was chosen to virtually screen the herbal data (a curated database of 989 herbal compounds). Then the hits (147 herbal compounds) were continued to be filtered by a docking process, and were tested in vitro successively. Finally, five of eighteen candidate compounds (272, 284, 300, 616 and 817) were found to have inhibition of CYP1A2 activity. The model developed in our study is efficient for in silico screening of large herbal databases in the identification of CYP1A2 inhibitors. It will play an important role to prevent the risk of herb–drug interactions at an early stage of the drug development process.

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.

Potential of pharmacokinetic profiling for detecting herbal interactions with drugs

The issue of herb-drug interactions has generated significant concern within the pharmaceutical industry and among regulatory authorities in recent years. Therefore, accurate models of predicting metabolic herb-drug interactions would be useful tools in efforts to avoid toxic adverse events. However, the majority of pharmacokinetic interactions listed for herbal medicinal products are based on theoretical predictions of the in vitro pharmacological effects of known constituents, which do not necessarily have to be the active ingredients. The prediction of herb-drug interactions is further complicated by the fact that pharmacokinetic data on active or (at least) known ingredients are often not available. The present article discusses the potential of pharmacokinetic profiling for detecting herb-drug interactions, using the most frequently cited interactions in the literature as examples. In particular, common mechanisms of herb-drug interactions are summarized, and the available experimental methods for detecting such interactions, as well as the limitations of these models, are critically evaluated. In addition, we discuss the question of whether the existing methods of detecting herb-drug interactions correlate with the clinical relevance. Effective screening tools that accurately predict metabolic herb-drug interactions would offer a tremendous advantage because it is not possible to study all potential herb-drug interactions in clinical trials.

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.

In vitro evaluation of human cytochrome P450 and P-glycoprotein-mediated metabolism of some phytochemicals in extracts and formulations of African potato

African potato (Hypoxis hemerocallidea, AP) is a traditional herbal medicine widely used as an immune booster and also for the treatment of various ailments such as urinary diseases, prostrate hypertrophy and cancer. Amongst the chemical components contained in AP, the norlignan glycoside, hypoxoside (HYP) is purported to be the most important phytochemical in terms of AP's medicinal value. Additional constituents in AP include the sterols, beta-sitosterol (BSS), stigmasterol (STG), and the stanol, stigmastanol (STN). The potential of extracts of AP, AP formulations as well as HYP, its aglycone rooperol (ROP) and the sterols to inhibit in vitro metabolism of drug marker substrates by human cytochrome P450 (CYP) enzymes such as CYP3A4, 3A5 and CYP19 were investigated. Samples were also assessed for their effect on drug transport proteins such as P-glycoprotein (P-gp). The effects on CYP-mediated metabolism were studied by fluorometric microtitre plate assay. The potential interaction with P-gp was investigated by measuring the efflux of the fluorescent dye rhodamine 123 (Rh 123) in the CaCo-2 (colon carcinoma) cell line. Various extracts of AP, AP formulations, only STG and the norlignans, in particular the aglycone ROP, exhibited inhibitory effects on CYP3A4-, 3A5- and 19-mediated metabolism. The extracts and the formulations that contained a significant amount of HYP showed high induction of P-gp compared to the positive control, ritonavir. Whilst extrapolation of the current in vitro findings to clinical effects may well be considered speculative, these in vitro data should be heeded as a signal of possible in vivo interactions. Appropriate measures are therefore necessary to explore the possibility of such in vitro-in vivo correlations.

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.

St. John's wort does not interfere with therapeutic drug monitoring of 12 commonly monitored drugs using immunoassays

St. John's wort, a popular herbal remedy for depression, is known to interact with many Western drugs because of the ability of its components to induce liver enzymes. Lower concentrations of various drugs due to increased clearance have been reported. Because immunoassays are commonly used in clinical laboratories for therapeutic drug monitoring, we studied the potential interference of St. John's wort with commonly monitored therapeutic drugs. Drug-free serum pools were supplemented with St. John's wort to achieve in vitro St. John's wort concentrations mimicking in vivo concentrations after both recommended use and overdose. Concentrations of digoxin, tricyclic antidepressants (TCAs), phenytoin, carbamazepine, theophylline, valproic acid, quinidine, phenobarbital, procainamide, and N-acetyl procainamide were measured in serum. Pooled serum specimens from patients who were taking a particular drug were also supplemented in vitro with concentrations of St. John's wort to investigate whether observed concentrations changed after supplementation with St. John's wort. The effect of St. John's wort on cyclosporine and tacrolimus (FK 506) was studied in whole blood. We found no significant interference from St. John's wort with any assay studied. Moreover, when drug-free serum was supplemented with very high concentrations of hypericin (2 microg/mL) and hyperforin (2 microg/mL) pure standard, we observed no apparent drug level with any immunoassay. The presence of both hypericin and hyperforin was also confirmed by thin layer chromatography (TLC) in both preparations of St. John's wort. We conclude that immunoassays may be used to measure levels of therapeutic drugs in patients who self-medicate with St. John's wort.

Induction of intestinal P-glycoprotein by St John's wort reduces the oral bioavailability of talinolol

St John's wort (SJW) is known to induce cytochrome P450 (CYP) 3A4 and P-glycoprotein through pregnane X-receptor activation. Our study evaluated the effects of long-term SJW administration on oral and intravenous pharmacokinetics of the nonmetabolized in vivo probe of P-glycoprotein, talinolol, in relation to intestinal P-glycoprotein expression. In a controlled, randomized study (N=9), the pharmacokinetics of oral (50 mg) and intravenous talinolol (30 mg) was determined before and after 12 days SJW (900 mg daily, Jarsin 300). Duodenal biopsies were taken and MDR1 genotypes assessed. SJW reduced the oral talinolol bioavailability by 25% (P=0.049) compared with water control. A 93% increase in oral clearance (P=0.177) and a 31% reduction in area under the serum concentration time curve (AUC; P=0.030) were observed. Renal and nonrenal clearance (CLNR), elimination half-life, peak serum drug concentration (Cmax), and time to reach Cmax were not significantly altered. After intravenous talinolol, SJW affected only CLNR (35% increase compared with water, P=0.006). SJW increased MDR1 messenger ribonucleic acid (mRNA) as well as P-glycoprotein levels in the duodenal mucosa. Subjects with the combined MDR1 genotype comprising 1236C>T, 2677G>T/A, and 3435C>T polymorphisms had lower intestinal MDR1 mRNA levels and displayed an attenuated inductive response to SJW as assessed by talinolol disposition. Long-term SJW decreased talinolol AUC with a corresponding increase in intestinal MDR1 expression, suggesting that SJW has a major inductive effect on intestinal P-glycoprotein. Interestingly, the magnitude of induction appeared to be affected by MDR1 genotype.

Use of Herbal Supplements and Vitamins in Plastic Surgery: A Practical Review

LEARNING OBJECTIVES

After studying this article, the participant should be able to: 1. Explain what governmental regulations control the labeling and distribution of herbal supplements. 2. List the more commonly used supplements and their reported benefits. 3. List the possible postoperative complications from consumption of the more commonly used herbal supplements. 4. Explain the preoperative management of patients using herbal supplements. 5. Know additional resources to consult when unanswered questions arise.

BACKGROUND

The American public spends over $5 billion per year on herbal supplements, and approximately 20 percent of all Americans use prescription medications concurrently with herbal supplements. As the number of people who take alternative medicines rises, there is growing awareness among health care providers of the need to become educated and to educate their patients on the effects that such supplementation may have on their health. As plastic surgeons, we have an added responsibility to become informed because of potential adverse interactions with other medications and anesthesia in the elective surgical patient.

METHODS

Literature regarding commonly encountered herbal supplements and vitamins was reviewed and summarized to include reported indications for use and potential adverse effects and interactions specific to the perioperative patient.

RESULTS

Abundant literature exists regarding herbal supplementation, but very little scientific evidence exists to advocate the use of the majority of supplements available on the market. In addition, little is known about the positive and negative interactions that these supplements are capable of producing, and those interactions that are known are based on case reports.

CONCLUSIONS

With the lack of quality scientific studies to support the efficacy of most herbal products available and the limited regulation of these products by the government, health care providers are faced with a significant public health dilemma. This article provides a brief overview of information published on commonly encountered herbal supplements and vitamins taken by plastic surgery patients.

Pharmacokinetic modelling of the interaction between St John's wort and ciclosporin A

AIMS

St John's wort (SJW) decreases the blood concentration of ciclosporin A (CsA), which may result in allograft rejection. In addition, the time course of this interaction is not parallel with the administration of SJW. We aimed to develop a pharmacokinetic model to predict the time profile of blood CsA concentrations during and after the intake of SJW.

METHODS

We developed a pharmacokinetic model incorporating turnover of detoxicating proteins, with the assumption that the amount of detoxicating proteins is in inverse proportion to the ratio of trough blood concentration to daily dose (C/D ratio) of CsA. First, we collected time profiles of blood CsA during and after the intake of SJW from the literature. Next, we analysed the relationship between D/C ratio and the daily dose of SJW at steady state. Subsequently, the developed model was simultaneously fitted to the time profiles of C/D ratios by using a nonlinear least-squares method to obtain model parameters.

RESULTS

The model analysis revealed that the induction of the detoxicating proteins by SJW was saturable with an elimination rate constant of the detoxicating proteins (ke) of 4.72 month(-1). Elimination half-life of the detoxicating proteins calculated from the ke value was 4.4 days, suggesting that the dose of CsA should be carefully monitored for up to 2 weeks after the cessation of SJW intake.

CONCLUSIONS

The present model may provide additional information for use in identifying optimal dosage regimens of CsA during and after the intake of SJW to prevent an adverse drug interaction between CsA and SJW.

Vitamin E but not St. John's wort mitigates leukopenia caused by cancer chemotherapy in rats

Dietary supplements are used by most patients with cancer. As nutraceuticals can interact with many drugs, this study investigated the effect of herbal remedies and vitamins on the toxicity of representative cancer chemotherapeutic agents. Fisher 344 rats were fed a standard cereal-based diet or the same diet with additional vitamin E in low (50 mg/kg) or high (750 mg/kg) concentrations, or with added St. John's wort (400 mg/kg). The LD50 was determined after the administration of chemotherapy drugs. Neither low or high vitamin E supplements nor St. John's wort significantly changed the LD50 for doxorubicin, docetaxel, or cyclophosphamide. The nadir white blood cell (WBC) count was significantly higher (P = 0.004) after docetaxel in rats supplemented with low-dose vitamin E, but the drop in WBC count from initial to nadir levels (Nfall) was greater in rats fed a diet containing high vitamin E supplementation (P = 0.04). Similarly, the Nfall was greater in the standard and high vitamin E dietary groups than in the low vitamin E group after cyclophosphamide (P = 0.03). No effect of vitamin E or St. John's wort supplementation occurred on doxorubicin pharmacokinetics. Neither vitamin E nor St. John's wort had an important effect on the mitochondrial deoxyribonucleic acid (DNA) damage caused by either doxorubicin or docetaxel. These data suggest that the leucopenia caused by some chemotherapeutic agents can be modified by dietary supplementation with vitamin E, but the effect seems to be dose-dependent. St. John's wort had neither a beneficial nor a detrimental effect on chemotherapy-induced toxicity.

Hypericum perforatum: a 'modern' herbal antidepressant: pharmacokinetics of active ingredients

Hypericum perforatum (St John's Wort [SJW]) counts among the most favourite herbal drugs, and is the only herbal alternative to classic synthetic antidepressants in the therapy of mild to moderate depression. Several clinical studies have been conducted to verify the effectiveness of ethanolic or methanolic extracts of SJW. Alcoholic SJW extracts are a mixture of substances with widely varying physical and chemical properties and activities. Hyperforin, a phloroglucinol derivative, is the main source of pharmacological effects caused by the consumption of alcoholic extracts of SJW in the therapy of depression. However, several studies indicate that flavone derivatives, e.g. rutin, and also the naphthodianthrones hypericin and pseudohypericin, take part in the antidepressant efficacy. In contrast to the amount of documentation concerning clinical efficacy, oral bioavailability and pharmacokinetic data about the active components are rather scarce. The hyperforin plasma concentration in humans was investigated in a small number of studies. The results of these studies indicate a relevant plasma concentration, comparable with that used in in vitro tests. Furthermore, hyperforin is the only ingredient of H. perforatum that could be determined in the brain of rodents after oral administration of alcoholic extracts. The plasma concentrations of the hypericins were, compared with hyperforin, only one-tenth and, until now, the hypericins could not be found in the brain after oral administration of alcoholic H. perforatum extracts or pure hypericin. Until now, the pharmacokinetic profile of the flavonoids in humans after oral administration of an alcoholic H. perforatum extract has been investigated in only one study. More data are available for rutin and the aglycone quercetin after administration of pure substances or other flavonoid sources.

Enhanced radiation sensitivity and radiation recall dermatitis (RRD) after hypericin therapy -- case report and review of literature

BACKGROUND

Modern radiotherapy (RT) reduces the side effects at organ at risk. However, skin toxicity is still a major problem in many entities, especially head and neck cancer. Some substances like chemotherapy provide a risk of increased side effects or can induce a "recall phenomenon" imitating acute RT-reactions months after RT. Moreover, some phototoxic drugs seem to enhance side effects of radiotherapy while others do not. We report a case of "radiation recall dermatitis" (RRD) one year after RT as a result of taking hypericin (St. John's wort).

CASE REPORT

A 65 year old man with completely resected squamous cell carcinoma of the epiglottis received an adjuvant locoregional RT up to a dose of 64.8 Gy. The patient took hypericin during and months after RT without informing the physician. During radiotherapy the patient developed unusual intensive skin reactions. Five months after RT the skin was completely bland at the first follow up. However, half a year later the patient presented erythema, but only within the area of previously irradiated skin. After local application of a steroid cream the symptoms diminished but returned after the end of steroid therapy. The anamnesis disclosed that the patient took hypericin because of depressive mood. We recommended to discontinue hypericin and the symptoms disappeared afterward.

CONCLUSION

Several drugs are able to enhance skin toxicity of RT. Furthermore, the effect of RRD is well known especially for chemotherapy agents such as taxans. However, the underlying mechanisms are not known in detail so far. Moreover, it is unknown whether photosensitising drugs can also be considered to increase radiation sensitivity and whether a recall phenomenon is possible. The first report of a hypericin induced RRD and review of the literature are presented. In clinical practise many interactions between drugs and radiotherapy were not noticed and if registered not published. We recommend to ask especially for complementary or alternative drugs because patients tend to conceal such medication as harmless.

Herbal product-drug interactions mediated by induction

Despite their common use, it is not widely recognized that herbal medicines can alter the efficacy of coadministered prescription drugs. Constituents in herbs interact with nuclear receptors to enhance metabolizing enzyme and/or transporter activity leading to reduced drug concentrations. Although St John's wort was the first and most frequently reported source of induction-style herb-drug interactions, this knowledge has not yet changed its current availability. This type of interaction is likely to be relevant to other herbal products. Caregivers need to be aware of the issues and options for therapeutic management.

Herbal remedies: effects on clinical laboratory tests

CONTEXT

Complementary and alternative medicine (herbal medicines) can affect laboratory test results by several mechanisms.

OBJECTIVE

In this review, published reports on effects of herbal remedies on abnormal laboratory test results are summarized and commented on.

DATA SOURCES

All published reports between 1980 and 2005 with the key words herbal remedies or alternative medicine and clinical laboratory test, clinical chemistry test, or drug-herb interaction were searched through Medline. The authors' own publications were also included. Important results were then synthesized.

DATA SYNTHESIS

Falsely elevated or falsely lowered digoxin levels may be encountered in a patient taking digoxin and the Chinese medicine Chan Su or Dan Shen, owing to direct interference of a component of Chinese medicine with the antibody used in an immunoassay. St John's wort, a popular herbal antidepressant, increases clearance of many drugs, and abnormally low cyclosporine, digoxin, theophylline, or protease inhibitor concentrations may be observed in a patient taking any of these drugs in combination with St John's wort. Abnormal laboratory results may also be encountered owing to altered pathophysiology. Kava-kava, chaparral, and germander cause liver toxicity, and elevated alanine aminotransferase, aspartate aminotransferase, and bilirubin concentrations may be observed in a healthy individual taking such herbal products. An herbal product may be contaminated with a Western drug, and an unexpected drug level (such as phenytoin in a patient who never took phenytoin but took a Chinese herb) may confuse the laboratory staff and the clinician.

CONCLUSIONS

Use of alternative medicines may significantly alter laboratory results, and communication among pathologists, clinical laboratory scientists, and physicians providing care to the patient is important in interpreting these results.

Evidence-based drug–herbal interactions

Due to the growing use of herbals and other dietary supplements healthcare providers and consumers need to know whether problems might arise from using these preparations in combination with conventional drugs. However, the evidence of interactions between natural products and drugs is based on known or suspected pharmacologic activity, data derived from in vitro or animal studies, or isolated case reports that frequently lack pertinent information. The usefulness of such information is questionable. More recently an increasing number of documented case reports, in vivo studies, and clinical trials have evaluated herbal-drug interactions. Results have sometimes been contradictory and more research is needed. Since there is a lack of rigorous studies that can establish the clinical significance of herb-drug interactions, an evidence-based evaluation of the current literature concerning commonly used herbal-drug interactions, as well as other dietary supplements, was conducted.

MDR- and CYP3A4-mediated drug–herbal interactions

According to recent epidemiological reports, almost 40% of American population use complimentary and alternative medicine (CAM) during their lifetime. Patients detected with HIV or cancer often consume herbal products especially St. John's wort (SJW) for antidepressants in combination with prescription medicines. Such self-administered herbal products along with prescribed medicines raise concerns of therapeutic activity due to possible drug-herbal interactions. P-glycoprotein (P-gp) and cytochrome P450 3A4 (CYP3A4) together constitute a highly efficient barrier for many orally absorbed drugs. Available literature, clinical reports and in vitro studies from our laboratory indicate that many drugs and herbal active constituents are substrates for both P-gp and CYP3A4. Results from clinical studies and case reports indicate that self-administered SJW reduce steady state plasma concentrations of amitriptyline, cyclosporine, digoxin, fexofenadine, amprenavir, indonavir, lopinavir, ritonavir, saquinavir, benzodiazepines, theophyline, irinotecan, midazolan and warfarin. This herbal agent has been also reported to cause bleeding and unwanted pregnancies when concomitantly administered with oral contraceptives. Most of these medicinal agents and SJW are substrates for P-gp and/or CYP3A4. In vitro studies from our laboratory suggest that short-term exposure with pure herbal agents such as hypericin, kaempferol and quercetin or extract of SJW resulted in higher uptake or influx of ritonavir and erythromycin. Hypericin, kaempferol and quercetin also caused a remarkable inhibition of cortisol metabolism with the percent intact cortisol values of 64.58%, 89.6% and 90.1%, respectively, during short-term in vitro experiments. Conversely, long-term exposure of herbal agents (hyperforin, kaempferol and quercetin) showed enhanced expression of CYP3A4 mRNA in Caco-2 cells. In another study, we observed that long-term exposure of hypericin, kaempferol, quercetin and silibinin resulted in higher MDR-1 mRNA expression in Caco-2 cells. Therefore, herbs can pharmacokinetically act as inhibitors or inducers. Medicinal agents that are substrates P-gp-mediated efflux and/or CYP-mediated metabolism are likely to be potential candidates for drug-herbal interactions. The duration of exposure of cells/healthy volunteers/animals to herbals appears to be critical for drug-herbal interaction. An increase in plasma drug concentration is possible during concomitant administration of SJW and prescribed drugs. In contrast, prolonged intake of herbal supplement followed by drug administration may result in subtherapeutic concentrations. Therefore, clinical implications of such drug herbal interactions depend on a variety of factors such as dose, frequency and timing of herbal intake, dosing regimen, route of drug administration and therapeutic range. In vitro screening techniques will play a major role in identifying possible herb-drug interactions and thus create a platform for clinical studies to emerge. Mechanisms of drug-herbal interaction have been discussed in this review article.

Hyperforin in St. John's wort drug interactions

Recently, interactions of herbal medicines with synthetic drugs came into focus of particular interest. In the past 3 years, more than 50 papers were published regarding interactions between St. John's wort (Hypericum perforatum L.; SJW) and prescription drugs. Co-medication with SJW resulted in decreased plasma concentrations of a number of drugs including amitriptyline, cyclosporine, digoxin, indinavir, irinotecan, warfarin, phenprocoumon, alprazolam, dextrometorphane, simvastatin, and oral contraceptives. Sufficient evidence from interaction studies and case reports indicate that SJW is a potent inducer of cytochrome P450 enzymes (particularly CYP3A4) and/or P-glycoprotein. Recent studies could show that the degree of enzyme induction by SJW correlates strongly with the amount of hyperforin found in the product. Products that do not contain substantial amounts of hyperforin (<1%) have not been shown to produce clinically relevant enzyme induction. On the other hand, some evidence suggests that hyperforin may also contribute to the antidepressant activity of SJW. However, clinical studies using SJW preparations with a low hyperforin amount (<1%) clearly demonstrated the superiority of this plant extract over placebo and its equivalence to imipramine and fluoxetine in the treatment of mild to moderate forms of depression. In the present paper clinical significant SJW interactions are critically evaluated against the background of hyperforin.

CYP3A4 and CYP2D6 inhibitory activities of Indonesian medicinal plants

Thirty samples of Indonesian medicinal plants were analyzed for their capacity to inhibit in vitro metabolism by human cytochrome P450 3A4 (CYP3A4) and CYP2D6 with a radiometric assay. The MeOH-soluble fractions of 25 samples, prepared from water extracts, demonstrated inhibitory activity more than 50% on the metabolism mediated by CYP3A4, and 21 samples on the metabolism mediated by CYP2D6. Among the MeOH-soluble fractions, Piper nigrum leaf showed the highest inhibitory activity against CYP3A4 (91.7%), and Punica granatum against CYP2D6 (98.1%). The water extracts of which MeOH-soluble fraction showed inhibitory activity more than 70% were fractionated with EtOAc. From the EtOAc-soluble fractions, Curcuma heyneana (67.0%), Pi. cubeba (75.0%), Pi. nigrum fruit (84.0%), Pi. nigrum leaf (85.8%), and Zingiber aromaticum (75.3%) demonstrated inhibitory activity more than 50% on the metabolism mediated by CYP3A4, but only Pi. nigrum fruit (72.8%) and Pi. nigrum leaf (69.1%) showed strong inhibitory activity against CYP2D6. For samples that showed more than 70% inhibition, their IC(50) values were determined. The most potent inhibitory activity against CYP3A4 (IC(50) value of 25 microg/ml) was found for the extract of Pi. nigrum leaf, while that of Catharanthus roseus showed the most potent inhibitory effect against CYP2D6 (IC(50) value of 11 microg/ml). These results should indicate once more the possibility of potential medicinal plant-drug interactions.

Ginkgo biloba: Evaluation of CYP2C9 Drug Interactions In Vitro and In Vivo

Ginkgo biloba extract is one of the most widely used herbal products in the United States. However, bleeding episodes in patients taking Ginkgo biloba and warfarin have been documented. Therefore, in vitro and in vivo inhibition studies were done to ascertain the influence of ginkgo on CYP2C9, the P-450 isozyme responsible for the metabolism of the most potent warfarin enantiomer, (S)-warfarin. Ginkgo extract inhibited human liver microsomal CYP2C9 with an apparent Ki=14.8 microg/mL, and the inhibition was increased by acid hydrolysis (apparent Ki=9.1 microg/mL). Two open-label, crossover pharmacokinetic studies in healthy subjects were performed using tolbutamide and diclofenac as probe CYP2C9 substrates. In contrast to the in vitro inhibition of CYP2C9, no interactions between Ginkgo biloba extract and CYP2C9 probe substrates were observed in vivo as evidenced by the lack of effect on the steady-state pharmacokinetics of diclofenac or on the urinary metabolic ratio of tolbutamide.

St John's wort modulation and developmental expression of multidrug transporters in the rat

Extracts of St John's wort (SJW) (Hypericum perforatum) are a potent inducer of enzymes of the cytochrome P450 system and of the transport protein P-glycoprotein, and interactions with a range of commonly prescribed medications have been described. In addition, recent experimental data suggest that, this otherwise safe treatment, could have some side effects when consumed during pregnancy and lactation. The aim of this study was to investigate, in Wistar rats, the effect of a treatment with high doses of SJW extract (100 and 1000 mg/kg/day) administered prenatally and during breastfeeding, on the level of transcripts of mdr1a, mdr1b, mrp1, mrp2 and cyp3A2 genes. All transcripts were detected in the liver, and their level of expression increased from fetuses to adults. SJW administration, at both dosages, caused a significant decrease of the levels of mdr1a, mdr1b, mrp1 and mrp2 in the livers of fetuses, and an increase in the levels of mdr1a, mdr1b, mrp2 and cyp3A2 in the mothers. In the other organs examined, a physiological regulation during ontogenesis was also evident, but SJW administration did not modify the expression level of the considered transcripts. These data suggest that the administration of the extract together with drugs that are substrates of transport proteins could be particularly hazardous during pregnancy.

Effect of St John's wort (Hypericum perforatum) on cytochrome P-450 activity in perfused rat liver

St. John's wort (Hypericum perforatum) is a popular over-the-counter dietary supplement and a herbal antidepressant that has been implicated in drug interactions with substrates of several cytochrome P-450 (CYP) isozymes. The effects of the St. John's wort extract (100 mg/kg, i.p., once daily for 10 days) on metabolic activity of CYP450 were assessed in the system of isolated perfused rat liver. The substrates used in this study were tolbutamide (CYP2C6), dextromethorphan (CYP2D2) and midazolam (CYP3A2). Validated HPLC method was used to quantify all compounds of interest. St. John's wort administration affected CYP activity, causing a significant decline in AUC of dextromethorphan [F(4,31)=1511, p<0.001; PLSD, p<0.001] and AUC of midazolam [F(3,25)=221, p<0.001; PLSD, p=0.035] and a significant increase in AUC of tolbutamide [F(3,26)=200, p<0.001; PLSD, p<0.001]. St. John's wort administration resulted in a significant induction of CYP2D2 and CYP3A2, and in a significant inhibition of CYP2C6 metabolic activities.

Time-dependent induction of midazolam-1-hydroxylation enzymes in rats treated with St. John's wort

Time-dependent effects of St. John's wort (SJW) on midazolam 1-hydroxylation were investigated in Wistar rats. Wistar rats treated with SJW (1000 mg/kg/d) for 1, 3, and 7 d were administered midazolam orally at a dose of 10 mg/kg. Oral clearance of midazolam in the SJW treated rats increased time dependently, and was significant after 7 d of treatment with SJW. The midazoram-1-hydroxylation activity in liver microsomes obtained from the SJW treated rats was significantly higher than in the control group. Linear correlation was observed between oral clearance and midazolam-1-hydroxylation activity in the liver microsomes, suggesting that CYP3A induction in liver mainly decreased the midazolam concentration in plasma. Immunoblotting revealed that the protein amount of CYP3A was induced within 3 d of SJW treatment. Since the midazolam-1-hydroxylation activity continuously increased for at least 7 d, the induction of CYP3A by SJW continued to cause interactions with drugs metabolized by CYP3A. It is important for persons receiving SJW for an extended time to consider its interactions with prescription drugs.