Herbal medicine yin zhi huang induces CYP3A4-mediated sulfoxidation and CYP2C19-dependent hydroxylation of omeprazole

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.

Inhibition and induction of CYP enzymes in humans: an update

The cytochrome P450 (CYP) enzyme family is the most important enzyme system catalyzing the phase 1 metabolism of pharmaceuticals and other xenobiotics such as herbal remedies and toxic compounds in the environment. The inhibition and induction of CYPs are major mechanisms causing pharmacokinetic drug–drug interactions. This review presents a comprehensive update on the inhibitors and inducers of the specific CYP enzymes in humans. The focus is on the more recent human in vitro and in vivo findings since the publication of our previous review on this topic in 2008. In addition to the general presentation of inhibitory drugs and inducers of human CYP enzymes by drugs, herbal remedies, and toxic compounds, an in-depth view on tyrosine-kinase inhibitors and antiretroviral HIV medications as victims and perpetrators of drug–drug interactions is provided as examples of the current trends in the field. Also, a concise overview of the mechanisms of CYP induction is presented to aid the understanding of the induction phenomena.

Interactions between clopidogrel and traditional Chinese medicine

The use of traditional Chinese medicine (TCM) has obtained more and more acceptance all over the world due to its multi-target and multi-level function characteristics. Clopidogrel is a major therapeutic option to reduce atherothrombotic events in patients with acute coronary syndrome, recent myocardial infarction, recent stroke or established peripheral arterial disease. These patients probably take TCM. Are there any interactions between clopidogrel and TCM? Whether TCM will affect the efficacy of clopidogrel or increase the adverse reactions of bleeding? Clarifying this information will help physicians make better use of TCM. A literature search was carried out using Web of Science, PubMed and the Cochrane Library to analyze the pharmacokinetic or pharmacodynamic interactions of clopidogrel and TCM. Some herbs can increase the AUC or C_max of clopidogrel, such as Scutellarin, Danggui, Gegen, Sauchinone and Dengzhan Shengmai capsules. Whereas others can decrease clopidogrel, for example, Ginkgo and Danshen. Furthermore, some herbs can increase the AUC or C_max of clopidogrel active metabolite, including Ginkgo and Xuesaitong tablet. And others can decrease the clopidogrel active metabolite, such as Scutellarin, Danshen, Fufang Danshen Dripping Pill and Dengzhan Shengmai capsules. Additionally, Schisandra chinensis, Danggui, Gegen and Fufang Danshen Dripping Pill can decrease the AUC or C_max of the clopidogrel inactive metabolite, while Curcumin on the contrary. The pharmacodynamics of Panax notoginseng, Notoginsenoside Ft1, Hypericum perforatum, Shexiang baoxin pills, Naoxintong capsule increased the antiplatelet activity compared with clopidogrel alone, while Danshen decreased the platelet inhibition. In adverse reactions, Danggui can enhance the adverse effects of clopidogrel on the bleeding time. With more awareness and understanding on potential drug-herb interactions of clopidogrel and TCM, it may be possible to combine clopidogrel with TCM herbs to yield a better therapeutic outcome.

Herb-Drug Interactions of Commonly Used Chinese Medicinal Herbs

With more and more popular use of traditional herbal medicines, in particular Chinese herbal medicines, herb-drug interactions have become a more and more important safety issue in the clinical applications of the conventional drugs. Researches in this area are increasing very rapidly. Herb-drug interactions are complicated due to the fact that multiple chemical components are involved, and these compounds may possess diverse pharmacological activities. Interactions can be in both pharmacokinetics and pharmacodynamics. Abundant studies focused on pharmacokinetic interactions of herbs and drugs. Herbs may affect the behavior of the concomitantly used drugs by changing their absorption, distribution, metabolism, and excretion. Studies on pharmacodynamics interactions of herbs and drugs are still very limited. Herb-drug interactions are potentially causing changes in drug levels and drug activities and leading to either therapeutic failure or toxicities. Sometime it can be fatal. The exposures to drugs, lacking of knowledge in the potential adverse herb-drug interactions, will put big risk to patients' safety in medical services. On the contrary, some interactions may be therapeutically beneficial. It may be used to help develop new therapeutic strategies in the future. This chapter is trying to review the development in the area of herb-drug interactions based on the recently published research findings. Information on the potential interactions among the commonly used Chinese medicinal herbs and conventional drugs is summarized in this chapter.

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.

In vitro inhibitory effects of plumbagin, the promising antimalarial candidate, on human cytochrome P450 enzymes

OBJECTIVE

To investigate the propensity of plumbagin to inhibit the three isoforms of human cytochrome P450 (CYP), i.e., CYP1A2, CYP2C19, and CYP3A4 using human liver microsomes in vitro.

METHODS

Inhibitory effects of plumbagin on the three human CYP isoforms were investigated using pooled human liver microsomes. Phenacetin O-deethylation, omeprazole hydroxylation and nifedipine oxidation were used as selective substrates for CYP1A2, CYP2C19 and CYP3A4 activities, respectively. Concentrations of paracetamol, 5-hydroxyomeprazole, and oxidized nifedipine were determined in microsomal incubation mixture using high-performance liquid chromatography.

RESULTS

Plumbagin showed significant inhibitory effects on all CYP isoforms, but with the most potent activity on CYP2C19-mediated omeprazole hydroxylation. The IC50 (concentration that inhibits enzyme activity by 50%) values of plumbagin and nootkatone (selective inhibitor) for CYP2C19 were (0.78 ± 0.01) and (27.31 ± 0.66) μM, respectively. The inhibitory activities on CYP1A2-mediated phenacetin O-deethylation and CYP3A4-mediated nifedipine oxidation were moderate. The IC50 values of plumbagin and α-naphthoflavone (selective inhibitor) for CYP1A2 were (1.39 ± 0.01) and (0.02 ± 0.36) μM, respectively. The corresponding IC50 values of plumbagin and ketoconazole (selective inhibitor) for CYP3A4 were (2.37 ± 0.10) and (0.18 ± 0.06) μM, respectively.

CONCLUSIONS

Clinical relevance of the interference of human drug metabolizing enzymes should be aware of for further development scheme of plumbagin as antimalarial drug when used in combination with other antimalarial drugs which are metabolized by these CYP isoforms.

Pharmacogenomics and herb-drug interactions: merge of future and tradition

The worldwide using of herb products and the increasing potential herb-drug interaction issue has raised enthusiasm on discovering the underlying mechanisms. Previous review indicated that the interactions may be mediated by metabolism enzymes and transporters in pharmacokinetic pathways. On the other hand, an increasing number of studies found that genetic variations showed some influence on herb-drug interaction effects whereas these genetic factors did not draw much attention in history. We highlight that pharmacogenomics may involve the pharmacokinetic or pharmacodynamic pathways to affect herb-drug interaction. We are here to make an updated review focused on some common herb-drug interactions in association with genetic variations, with the aim to help safe use of herbal medicines in different individuals in the clinic.

A randomized controlled trial of adjunctive Bunchang Naoxintong Capsule (步长脑心通胶囊) versus maintenance dose clopidogrel in patients with CYP2C19*2 polymorphism

OBJECTIVE

To determine the impact of adjunctive Buchang Naoxintong Capsule (, NXT) on dual antiplatelet therapy in patients with cytochrome P450 2C19*2 (CYP2C19*2) polymorphism undergoing percutaneous coronary intervention (PCI).

METHODS

Ninety patients with CYP2C19*2 polymorphism were enrolled, and their genotypes were confirmed by polymerase chain reaction (PCR). The patients were randomly assigned to receive either adjunctive NXT (triple group, 45 cases) or dual antiplatelet therapy (dual group, 45 cases) using a computer-generated randomization sequence and sealed envelopes. Platelet function was assessed at baseline and 7 days after treatment with conventional aggregometry. Subsequent major adverse cardiovascular events (MACE, including sudden cardiac arrest and acute coronary syndrome) were recorded during a 12-month follow-up.

RESULTS

Baseline platelet function measurements were similar in both groups. After 7 days, percent inhibitions of maximum platelet aggregation and late platelet aggregation were significantly greater in the triple versus dual group (42.3%±16.0% vs. 20.8%±15.2%, P<0.01, and 54.7%±18.3% vs. 21.5%±29.2%, P<0.01, respectively). During the 12-month follow-up, the rate of subsequent MACE (6/45) was significantly lower in the triple group compared with the dual group (14/45; P<0.05).

CONCLUSION

Adjunctive NXT to maintenance dose clopidogrel (75 g) could enhance the antiplatelet effect and decrease subsequent MACE in patients with the CYP2C19*2 polymorphism undergoing PCI.

Pharmacokinetic drug interaction profile of omeprazole with adverse consequences and clinical risk management

BACKGROUND

Omeprazole, a proton pump inhibitor (PPI), is widely used for the treatment of dyspepsia, peptic ulcer, gastroesophageal reflux disease, and functional dyspepsia. Polypharmacy is common in patients receiving omeprazole. Drug toxicity and treatment failure resulting from inappropriate combination therapy with omeprazole have been reported sporadically. Systematic review has not been available to address the pharmacokinetic drug-drug interaction (DDI) profile of omeprazole with adverse consequences, the factors determining the degree of DDI between omeprazole and comedication, and the corresponding clinical risk management.

METHODS

Literature was identified by performing a PubMed search covering the period from January 1988 to March 2013. The full text of each article was critically reviewed, and data interpretation was performed.

RESULTS

Omeprazole has actual adverse influences on the pharmacokinetics of medications such as diazepam, carbamazepine, clozapine, indinavir, nelfinavir, atazanavir, rilpivirine, methotrexate, tacrolimus, mycophenolate mofetil, clopidogrel, digoxin, itraconazole, posaconazole, and oral iron supplementation. Meanwhile, low efficacy of omeprazole treatment would be anticipated, as omeprazole elimination could be significantly induced by comedicated efavirenz and herb medicines such as St John's wort, Ginkgo biloba, and yin zhi huang. The mechanism for DDI involves induction or inhibition of cytochrome P450, inhibition of P-glycoprotein or breast cancer resistance protein-mediated drug transport, and inhibition of oral absorption by gastric acid suppression. Sometimes, DDIs of omeprazole do not exhibit a PPI class effect. Other suitable PPIs or histamine 2 antagonists may be therapeutic alternatives that can be used to avoid adverse consequences. The degree of DDIs associated with omeprazole and clinical outcomes depend on factors such as genotype status of CYP2C19 and CYP1A2, ethnicity, dose and treatment course of precipitant omeprazole, pharmaceutical formulation of object drug (eg, mycophenolate mofetil versus enteric-coated mycophenolate sodium), other concomitant medication (eg, omeprazole-indinavir versus omeprazole-indinavir-ritonavir), and administration schedule (eg, intensified dosing of mycophenolate mofetil versus standard dosing).

CONCLUSION

Despite the fact that omeprazole is one of the most widely prescribed drugs internationally, clinical professionals should enhance clinical risk management on adverse DDIs associated with omeprazole and ensure safe combination use of omeprazole by rationally prescribing alternatives, checking the appropriateness of physician orders before dispensing, and performing therapeutic drug monitoring.

In Vitro Assessment of Cytochrome P450 2C19 Potential of Naoxintong

The effects of Buchang Naoxintong Capsules (BNCs) on S-mephenytoin 4′-hydroxylation activities in human liver microsomes in vitro were assessed. Human liver microsome was prepared by different ultracentrifugation. Human liver microsome incubation experiment was carried out to assay BNC on S-mephenytoin 4′-hydroxylation activities. The 4′-hydroxylation of S-mephenytoin, a representative substrate toward CYP2C19, was increased by phenytoin sodium (positive control). After the incubation, the metabolites of the substrates (4′-OH-mephenytoin) were determined by HPLC. Results showed that both phenytoin sodium and BNC showed obvious increase effect on CYP2C19. The enzymatic reaction of BNC was observed with concentrations ranging from 5 μg/mL to 250 μg/mL. Compared to blank, the increase effect of BNC showed significant difference from the beginning of concentration of 150 μg/mL (P < 0.001). The conclusion was that BNC showed obvious increase effect on the catalytic activities of drug-metabolising CYP2C19 enzyme.

Trade herbal products and induction of CYP2C19 and CYP2E1 in cultured human hepatocytes

The aim of this study was to evaluate in vitro the dose-dependent induction potential of six commonly used trade herbal products on CYP2C19 and CYP2E1 metabolic activities in cultured human hepatocytes. S-mephenytoin and chlorzoxazone were used as specific CYP substrates, respectively, and rifampicin was used as a positive induction control for both enzymes. The hepatocytes were exposed to herbal extracts in increasing and biological relevant concentrations for 72 hrs and CYP substrate metabolites were quantified by validated HPLC methodologies. The major findings were that St John's wort was the most potent CYP-modulating herb, showing a dose-dependent induction/inhibition of both CYP2C19 and CYP2E1, with induction at low dosages and inhibition at higher. Ginkgo biloba showed an induction/inhibition profile towards CYP2C19 which was similar but weaker than that observed for St John's wort. If cooperative mechanisms are involved is still an open question. Common sage induced CYP2C19 in a log-linear dose-dependent manner with increasing concentrations. Common valerian was a weak inducer of CYP2C19, while horse chestnut and cone flower were characterized as non-inducers of CYP2C19. Only St John's wort showed an inductive effect towards CYP2E1. In addition to St John's wort, Gingko biloba and common sage should be considered as possible candidates for clinically relevant drug-herb interactions with selected CYP2C19 substrates.