Effects of Garlic on Cytochromes P450 2C9- and 3A4-Mediated Drug Metabolism in Human Hepatocytes

Evaluation potential effects of Picroside II on cytochrome P450 enzymes in vitro and in vivo

ETHNOPHARMACOLOGY RELEVANCE

Picrorhiza scrophulariiflora Pennell, a well-known Chinese herb, has been traditionally utilized as an antioxidant and anti-inflammatory agent. One of its main bioactive components is Picroside II, a glycoside derivative. However, there is limited information on the effects of Picroside II on the activity of cytochrome P450 (CYP) enzymes nor on potential herb-drug interactions are rarely studied.

AIM OF THE STUDY

The purpose of the study was to investigate the effects of Picroside II on the activity of cytochrome P450 enzymes in vitro and in vivo and its potential herb-drug interactions.

MATERIALS AND METHODS

Specific probe substrates were employed to assess the effect of Picroside II on the activity of P450 enzymes. The inhibitory effects of Picroside II on CYP enzymes were assayed both in human (i.e., 1A, 2C9, 2C19, 2D6, 2E1, and 3A) and rat (i.e., 1A, 2C6/11, 2D1, 2E1, and 3A) liver microsomes in vitro. The inductive effects were investigated in rats following oral gavage of 2.5 mg/kg and 10 mg/kg Picroside II. A specific Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry (UPLC-MS/MS) method was developed to determine the formation of specific metabolites.

RESULTS

Enzyme inhibition results showed that Picroside II (0.5-200 μM) had no evident inhibitory effects on rat and human liver microsomes in vitro. Interestingly, the administration of multiple doses of 10 mg/kg Picroside II inhibited the activity of CYP2C6/11 by reducing the rate of formation of 4-hydroxydiclofenac and 4-hydroxymephenytoin, while Picroside II at 2.5 mg/kg increased the activity of CYP3A by promoting the formation of 1-hydroxymidazolam and 6-hydroxychlorzoxazone in rats. In addition, there were negligible effects on CYP1A, CYP2D1, and CYP2E1 in rats.

CONCLUSIONS

The results indicated that Picroside II modulated the activities of CYP enzymes and was involved in CYP2C and CYP3A medicated herb-drug interactions. Therefore, careful monitoring is necessary when Picroside II is used in combination with related conventional drugs.

Allicin promotes autophagy and ferroptosis in esophageal squamous cell carcinoma by activating AMPK/mTOR signaling

The antitumor effects of allicin have been demonstrated in various cancers. However, whether allicin improves esophageal squamous cell carcinoma (ESCC) has not yet been explored. The present study aimed to explore the function and underlying mechanism of action of allicin in ESCC treatment. Our data showed that allicin significantly suppressed ESCC cell proliferation in a dose- and time-dependent manner. A green fluorescent protein-light chain 3 (LC3) transfection assay showed that autophagosomes were elevated in ESCC cells treated with allicin compared with control ESCC cells and that 3-methyladenine (an autophagy inhibitor) reversed allicin-induced LC3 puncta. Furthermore, allicin significantly elevated the ratio of LC3II/LC3I but decreased p62 expression in ESCC cells. Allicin also increased adenosine monophosphate-activated protein kinase (AMPK) phosphorylation but decreased that of the mechanistic target of rapamycin kinase (mTOR), which then induced the elevation of autophagy-related 5 and autophagy-related 7 proteins in ESCC cells. Furthermore, allicin treatment increased the expression of nuclear receptor coactivator 4 (a selective cargo receptor) but suppressed the expression of ferritin heavy chain 1 (the major intracellular iron-storage protein) in ESCC cells and elevated malondialdehyde and Fe2+ production levels. In vivo assays showed that allicin significantly decreased tumor weight and volume. In summary, allicin may induce cell death in ESCC cells by activating AMPK/mTOR-mediated autophagy and ferroptosis. Therefore, allicin may have excellent potential for use in the treatment of ESCC.

Pharmacokinetic Outcomes of the Interactions of Antiretroviral Agents with Food and Supplements: A Systematic Review and Meta-Analysis

Because pharmacokinetic changes in antiretroviral drugs (ARV), due to their concurrent administration with food or nutritional products, have become a clinical challenge, it is necessary to monitor the therapeutic efficacy of ARV in people living with the human immunodeficiency virus (PLWH). A systematic review and meta-analysis were conducted to clarify the pharmacokinetic outcomes of the interaction between supplements such as food, dietary supplements, and nutrients, and ARV. Twenty-four articles in both healthy subjects and PLWH were included in the qualitative analysis, of which five studies were included in the meta-analysis. Food−drug coadministration significantly increased the time to reach maximum concentration (tmax) (p < 0.00001) of ARV including abacavir, amprenavir, darunavir, emtricitabine, lamivudine, zidovudine, ritonavir, and tenofovir alafenamide. In addition, the increased maximum plasma concentration (Cmax) of ARV, such as darunavir, under fed conditions was observed. Area under the curve and terminal half-life were not significantly affected. Evaluating the pharmacokinetic aspects, it is vital to clinically investigate ARV and particular supplement interaction in PLWH. Educating patients about any potential interactions would be one of the effective recommendations during this HIV epidemic.

Complementary and alternative medicine (CAM) supplements in cancer outpatients: analyses of usage and of interaction risks with cancer treatment

Purpose

The aim of our study was to analyze the use of complementary and alternative medicine (CAM) supplements, identify possible predictors, and analyze and compile potential interactions of CAM supplements with conventional cancer therapy.

Methods

We included outpatient cancer patients treated at a German university hospital in March or April 2020. Information was obtained from questionnaires and patient records. CAM–drug interactions were identified based on literature research for each active ingredient of the supplements consumed by the patients.

Results

37.4% of a total of 115 patients consumed CAM supplements. Potential interactions with conventional cancer treatment were identified in 51.2% of these patients. All types of CAM supplements were revealed to be a potential source for interactions: vitamins, minerals, food and plant extracts, and other processed CAM substances. Younger age (< 62 years) (p = 0.020, φc = 0.229) and duration of individual cancer history of more than 1 year (p = 0.006, φc = 0.264) were associated with increased likelihood of CAM supplement use. A wide range of different CAM supplement interactions were reviewed: effects of antioxidants, cytochrome (CYP) interactions, and specific agonistic or antagonistic effects with cancer treatment.

Conclusion

The interaction risks of conventional cancer therapy with over-the-counter CAM supplements seem to be underestimated. Supplements without medical indication, as well as overdoses, should be avoided, especially in cancer patients. To increase patient safety, physicians should address the risks of interactions in physician–patient communication, document the use of CAM supplements in patient records, and check for interactions.

Herb-drug interactions in diabetes mellitus: A review based on pre-clinical and clinical data

Global diabetes epidemic is the major cause of fatality and lethality. As per IDF 2019 report, diabetes caused 4.2 million deaths, approximately 463 million people are living with diabetes and by 2045, this will rise to 700 million. Nowadays, the physicians and common people in both developed and developing countries are using medicinal plants and their formulations to treat diseases with the postulation that organic commodities are safe for consumption. These plants may act as inhibitors or inducers of the Cytochrome P450 or transport and efflux proteins or both and may alter gastrointestinal, renal functions leading to Herb-Drug Interactions. This review intends to focus on the frequently employed medicinal plants, their traditional uses, their Cytochrome P450 inhibition or induction activity, phytochemical, and pharmacological effects, established HDI with the help of in vitro tools, in vivo pharmacokinetics and pharmacodynamics studies to understand the impact of herbs on ADME of the drug and whether it is beneficial, harmful or has no effect respectively. This review will help the physicians and other health care professionals as a reference guide to update their knowledge and expertise about HDI. However, more quality research in this area is needed to evaluate the efficacy of many herbal medicines, thereby reducing side effects and improving the safety of patients.

Herb-drug interaction between Styrax and warfarin: Molecular basis and mechanism

BACKGROUND

Styrax, one of the most famous folk medicines, has been frequently used for the treatment of cardiovascular diseases and skin problems in Asia and Africa. It is unclear whether Styrax or Styrax-related herbal medicines may trigger clinically relevant herb-drug interactions.

PURPOSE

This study was carried out to investigate the inhibitory effects of Styrax on human cytochrome P450 enzymes (CYPs) and to clarify whether this herb may modulate the pharmacokinetic behavior of the CYP-substrate drug warfarin when co-administered.

STUDY DESIGN

The inhibitory effects of Styrax on CYPs were assayed in human liver microsomes (HLM), while the pharmacokinetic interactions between Styrax and warfarin were investigated in rats. The bioactive constituents in Styrax with strong CYP3A inhibitory activity were identified and their inhibitory mechanisms were carefully investigated.

METHODS

The inhibitory effects of Styrax on human CYPs were assayed in vitro, while the pharmacokinetic interactions between Styrax and warfarin were studied in rats. Fingerprinting analysis of Styrax coupled with LC-TOF-MS/MS profiling and CYP inhibition assays were used to identify the constituents with strong CYP3A inhibitory activity. The inhibitory mechanism of oleanonic acid (the most potent CYP3A inhibitor occurring in Styrax) against CYP3A4 was investigated by a panel of inhibition kinetics analyses and in silico analysis.

RESULTS

In vitro assays demonstrated that Styrax extract strongly inhibited human CYP3A and moderately inhibited six other tested human CYPs, as well as potently inhibited warfarin 10-hydroxylation in liver microsomes from both humans and rats. In vivo assays demonstrated that compared with warfarin given individually in rats, Styrax (100 mg/kg) significantly prolonged the plasma half-life of warfarin by 2.3-fold and increased the AUC_(0-inf) of warfarin by 2.7-fold when this herb was co-administrated with warfarin (2 mg/kg) in rats. Two LC fractions were found with strong CYP3A inhibitory activity and the major constituents in these fractions were characterized by LC-TOF-MS/MS. Five pentacyclic triterpenoid acids (including epibetulinic acid, betulinic acid, betulonic acid, oleanonic acid and maslinic acid) present in Styrax were potent CYP3A inhibitors, and oleanonic acid was a competitive inhibitor against CYP3A-mediated testosterone 6β-hydroxylation.

CONCLUSION

Styrax and the pentacyclic triterpenoid acids occurring in this herb strongly modulate the pharmacokinetic behavior of warfarin via inhibition of CYP3A.

The mechanisms of pharmacokinetic food-drug interactions - A perspective from the UNGAP group

The simultaneous intake of food and drugs can have a strong impact on drug release, absorption, distribution, metabolism and/or elimination and consequently, on the efficacy and safety of pharmacotherapy. As such, food-drug interactions are one of the main challenges in oral drug administration. Whereas pharmacokinetic (PK) food-drug interactions can have a variety of causes, pharmacodynamic (PD) food-drug interactions occur due to specific pharmacological interactions between a drug and particular drinks or food. In recent years, extensive efforts were made to elucidate the mechanisms that drive pharmacokinetic food-drug interactions. Their occurrence depends mainly on the properties of the drug substance, the formulation and a multitude of physiological factors. Every intake of food or drink changes the physiological conditions in the human gastrointestinal tract. Therefore, a precise understanding of how different foods and drinks affect the processes of drug absorption, distribution, metabolism and/or elimination as well as formulation performance is important in order to be able to predict and avoid such interactions. Furthermore, it must be considered that beverages such as milk, grapefruit juice and alcohol can also lead to specific food-drug interactions. In this regard, the growing use of food supplements and functional food requires urgent attention in oral pharmacotherapy. Recently, a new consortium in Understanding Gastrointestinal Absorption-related Processes (UNGAP) was established through COST, a funding organisation of the European Union supporting translational research across Europe. In this review of the UNGAP Working group "Food-Drug Interface", the different mechanisms that can lead to pharmacokinetic food-drug interactions are discussed and summarised from different expert perspectives.

Warfarin Safety: A Cross-Sectional Study of the Factors Associated with the Consumption of Medicinal Plants in a Brazilian Anticoagulation Clinic

OBJECTIVE

The aim of this study was to analyze factors associated with the consumption of medicinal plants by patients being treated with warfarin in a Brazilian anticoagulation clinic and to study the safety of medicinal plant use in patients on warfarin therapy.

METHODS

The study was performed as an observational cross-sectional analysis. Study participants were outpatients on long-term warfarin therapy for at least 2 months for atrial fibrillation or prosthetic cardiac valves. Interviews were carried out concerning information about the habits of medicinal herb consumption, and logistic regression analysis was performed to identify factors associated with the consumption of herbs. The scientific names of the medicinal plants were identified to search for information on the effects on the hemostasis of the interactions between the medicinal herbs reported and warfarin.

RESULTS

The mean age of the 273 patients included was 60.8 years; 58.7% were women. Medicinal plants were used by 67% of the participants. No association between demographic and clinical data and the use of medicinal plants was identified. Patients reported a total of 64 different plants, primarily consumed in the form of tea. The plants were mainly used to treat respiratory tract and central nervous system disorders. About 40% of the plants cited have been reported to potentially interfere with the anticoagulation therapy, principally by potentiating the effects of warfarin, which could, increase the risk of bleeding.

CONCLUSION

The use of medicinal plants was highly common and widespread in patients receiving warfarin as an anticoagulation therapy. Univariate analysis of variables associated with the consumption of herbs showed no statistically significant difference in the consumption of medicinal plants for any of the sociodemographic and clinical data. The medicinal plants that were reportedly consumed by the patients could affect hemostasis. This study reinforces the need for further studies evaluating the habits of patients consuming medicinal plants and their clinical implications, and will help to design strategies to manage the risks associated with warfarin-herbal interactions.

Research and Development of Atractylodes lancea (Thunb) DC. as a Promising Candidate for Cholangiocarcinoma Chemotherapeutics

Treatment and control of cholangiocarcinoma (CCA): the bile duct cancer is limited by the lack of effective chemotherapeutic drugs and alternative drugs are needed, particularly those from natural sources. This article reviews steps of research and development of Atractylodes lancea (Thunb) DC. (AL) as potential candidate for CCA chemotherapy, with adoption of the reverse pharmacology approach. Major steps include (1) reviewing of existing information on its phytochemistry and pharmacological properties, (2) screening of its activities against CCA, (3) standardization of AL, (4) nonclinical studies to evaluate anti-CCA activities, (5) phytochemistry and standardization of AL extract, (6) development of oral pharmaceutical formulation of standardized AL extract, and (7) toxicity testing of oral pharmaceutical formulation of standardized AL extract. Results from a series of our study confirm anti-CCA potential and safety profiles of both the crude extract and the finished product (oral pharmaceutical formulation of the standardized AL extract). Phases I and II clinical trials of the product to confirm tolerability and efficacy in healthy subjects and patients with advanced stage CCA will be carried out soon.

Assessment of cytochrome P450 inhibition and induction potential of lupeol and betulin in rat liver microsomes

BACKGROUND

Lupeol and betulin are triterpenoids that are majorly found in dietary substances. The aim of present study was to investigate the inhibition and induction potential of lupeol and betulin on cytochrome P450 (CYP)1A2, CYP2C11, CYP2D6 and CYP3A2 activities in rat liver microsomes.

METHODS

The inhibition and induction studies were conducted using ethoxy resorufin-O-deethylase (CYP1A2), tolbutamide hydroxylase (CYP2C9), and midazolam hydroxylase (CYP3A4) activity assays. In vitro inhibition study was evaluated by incubating lupeol and betulin (1, 3, 10, 30 and 100 μM) with rat liver microsomes, and the metabolite formation was analyzed by high-performance liquid chromatography. The induction study was conducted by administering lupeol (20 mg/kg) and betulin (50 mg/kg) intraperitoneally for 14 days to rats followed by liver isolation and microsome preparation.

RESULTS

The IC50 values in inhibition studies were found to be 59.42 μM (CYP1A2), >100 μM (CYP2C11, CYP2D6, CYP3A2) for lupeol, 52.24 μM (CYP1A2), and >100 μM (CYP2C9, CYP2D6, CYP3A2) for betulin. There was no significant modification observed in the CYP450 isoforms, indicating neither inhibition nor induction potential of lupeol and betulin.

CONCLUSIONS

Lupeol and betulin have very low propensity to interact with CYP enzyme, suggesting no CYP inhibitory and inducing potential in rat liver microsomes.

Oral antineoplastic agent interactions with medicinal plants and food: an issue to take into account

OBJECTIVE

To review interactions between oral antineoplastic agents (OAAs) for the treatment of solid and hematological tumors and common food and medicinal plants.

MATERIALS AND METHODS

All potential interactions between OAAs, medicinal plants and food were reviewed. OAAs were considered to be drugs for oral administration that have direct antitumor activity and were approved by the European Medicines Agency in April 2015. We performed the literature search in Pubmed(®) considering only medicinal plants and food. In addition, available data were analyzed from each OAA in secondary data sources taken from Thomson Micromedex(®) and Lexi-comp(®), as well as in the summary of product characteristics.

RESULTS

Fifty-eight OAAs were analyzed. We found interactions in 60.3 % of OAAs. Those with most interactions described were: imatinib and procarbazine (4 interactions) and erlotinib, vemurafenib, pomalidomide, medroxyprogesterone and methotrexate (3 interactions).

MEDICINAL PLANTS

We found 39 interactions (74.4 % important). St. John's wort was the medicinal plant with most interactions (92.6 % were considered important). The rest were: important (ginseng-imatinib, methotrexate-cola and tobacco-erlotinib and tobacco-pomalidomide) and moderate (caffeine-vemurafenib/medroxyprogesterone, medroxyprogesterone-ruxolitinib/St. John's wort, garlic-anagrelide and ginseng-procarbazine).

FOODS

Twenty-six interactions (61.5 % important). Grapefruit had most interactions (82.4 % were considered important). The rest were: important (alcohol-procarbazine) and moderate (dairy-estramustine, methotrexate-ethanol, procarbazine-tyramine, vitamin A-tretinoin/bexarotene and grapefruit-bexarotene/etoposide/sunitinib).

CONCLUSION

A review of interactions of medicinal plants and food should be taken into account in the management of OAAs, since more than half have interactions with MPs and food, of which 70.3 % are considered important. The most relevant are HSJ, grapefruit, ginseng and tobacco. This review is intended to serve as a support to all healthcare professionals at the time of prescribing or dispensing OAAs.

Oral antineoplastic agent interactions with medicinal plants and food: an issue to take into account

OBJECTIVE

To review interactions between oral antineoplastic agents (OAAs) for the treatment of solid and hematological tumors and common food and medicinal plants.

MATERIALS AND METHODS

All potential interactions between OAAs, medicinal plants and food were reviewed. OAAs were considered to be drugs for oral administration that have direct antitumor activity and were approved by the European Medicines Agency in April 2015. We performed the literature search in Pubmed(®) considering only medicinal plants and food. In addition, available data were analyzed from each OAA in secondary data sources taken from Thomson Micromedex(®) and Lexi-comp(®), as well as in the summary of product characteristics.

RESULTS

Fifty-eight OAAs were analyzed. We found interactions in 60.3 % of OAAs. Those with most interactions described were: imatinib and procarbazine (4 interactions) and erlotinib, vemurafenib, pomalidomide, medroxyprogesterone and methotrexate (3 interactions).

MEDICINAL PLANTS

We found 39 interactions (74.4 % important). St. John's wort was the medicinal plant with most interactions (92.6 % were considered important). The rest were: important (ginseng-imatinib, methotrexate-cola and tobacco-erlotinib and tobacco-pomalidomide) and moderate (caffeine-vemurafenib/medroxyprogesterone, medroxyprogesterone-ruxolitinib/St. John's wort, garlic-anagrelide and ginseng-procarbazine).

FOODS

Twenty-six interactions (61.5 % important). Grapefruit had most interactions (82.4 % were considered important). The rest were: important (alcohol-procarbazine) and moderate (dairy-estramustine, methotrexate-ethanol, procarbazine-tyramine, vitamin A-tretinoin/bexarotene and grapefruit-bexarotene/etoposide/sunitinib).

CONCLUSION

A review of interactions of medicinal plants and food should be taken into account in the management of OAAs, since more than half have interactions with MPs and food, of which 70.3 % are considered important. The most relevant are HSJ, grapefruit, ginseng and tobacco. This review is intended to serve as a support to all healthcare professionals at the time of prescribing or dispensing OAAs.

Pharmacokinetic Interactions between Drugs and Botanical Dietary Supplements

The use of botanical dietary supplements has grown steadily over the last 20 years despite incomplete information regarding active constituents, mechanisms of action, efficacy, and safety. An important but underinvestigated safety concern is the potential for popular botanical dietary supplements to interfere with the absorption, transport, and/or metabolism of pharmaceutical agents. Clinical trials of drug-botanical interactions are the gold standard and are usually carried out only when indicated by unexpected consumer side effects or, preferably, by predictive preclinical studies. For example, phase 1 clinical trials have confirmed preclinical studies and clinical case reports that St. John's wort (Hypericum perforatum) induces CYP3A4/CYP3A5. However, clinical studies of most botanicals that were predicted to interact with drugs have shown no clinically significant effects. For example, clinical trials did not substantiate preclinical predictions that milk thistle (Silybum marianum) would inhibit CYP1A2, CYP2C9, CYP2D6, CYP2E1, and/or CYP3A4. Here, we highlight discrepancies between preclinical and clinical data concerning drug-botanical interactions and critically evaluate why some preclinical models perform better than others in predicting the potential for drug-botanical interactions. Gaps in knowledge are also highlighted for the potential of some popular botanical dietary supplements to interact with therapeutic agents with respect to absorption, transport, and metabolism.

The utility of metabolic activation mixtures containing human hepatic post-mitochondrial supernatant (S9) for in vitro genetic toxicity assessment

In vitro genotoxicity assessment routinely employs an exogenous metabolic activation mixture to simulate mammalian metabolism. Activation mixtures commonly contain post-mitochondrial liver supernatant (i.e. S9) from chemically induced Sprague Dawley rats. Although Organization for Economic Cooperation and Development (OECD) test guidelines permit the use of other S9 preparations, assessments rarely employ human-derived S9. The objective of this study is to review and evaluate the use of human-derived S9 for in vitro genetic toxicity assessment. All available published genotoxicity assessments employing human S9 were compiled for analysis. To facilitate comparative analyses, additional matched Ames data using induced rat liver S9 were obtained for certain highly cited chemicals. Historical human and induced rat S9 quality control reports from Moltox were obtained and mined for enzyme activity and mutagenic potency data. Additional in vitro micronucleus data were experimentally generated using human and induced rat S9. The metabolic activity of induced rat S9 was found to be higher than human S9, and linked to high mutagenic potency results. This study revealed that human S9 often yields significantly lower Salmonella mutagenic potency values, especially for polycyclic aromatic hydrocarbons, aflatoxin B1 and heterocyclic amines (~3- to 350-fold). Conversely, assessment with human S9 activation yields higher potency for aromatic amines (~2- to 50-fold). Outliers with extremely high mutagenic potency results were observed in the human S9 data. Similar trends were observed in experimentally generated mammalian micronucleus cell assays, however human S9 elicited potent cytotoxicity L5178Y, CHO and TK6 cell lines. Due to the potential for reduced sensitivity and the absence of a link between enzyme activity levels and mutagenic potency, human liver S9 is not recommended for use alone in in vitro genotoxicity screening assays; however, human S9 may be extremely useful in follow-up tests, especially in the case of chemicals with species-specific metabolic differences, such as aromatic amines.

Inhibitory Activities of Thai Medicinal Plants with Promising Activities Against Malaria and Cholangiocarcinoma on Human Cytochrome P450

Malaria and cholangiocarcinoma remain important public health problems in tropical countries including Southeast Asian nations. Newly developed chemotherapeutic and plant-derived drugs are urgently required for the control of both diseases. The aim of the present study was to investigate the propensity to inhibit cytochrome P450-mediated hepatic metabolism (CYP1A2, CYP2C19, CYP2D6 and CYP3A4) of the crude ethanolic extract of eight Thai medicinal plants with promising activities against malaria and cholangiocarcinoma, using human liver microsomes in vitro. Piper chaba Linn. (PC) and Atractylodes lancea (thung.) DC. (AL) exhibited the most potent inhibitory activities on CYP1A2-mediated phenacetin O-deethylation with mean IC50 of 0.04 and 0.36 µg/mL, respectively. Plumbago indica Linn. (PI) and Dioscorea membranacea Pierre. (DM) potently inhibited CYP2C19-mediated omeprazole 5-hydroxylation (mean IC50 4.71 and 6.92 µg/mL, respectively). DM, Dracaena loureiri Gagnep. (DL) and PI showed the highest inhibitory activities on dextromethorphan O-demethylation (mean IC50 2.93-9.57 µg/mL). PC, DM, DL and PI exhibited the most potent inhibitory activities on CYP3A4-mediated nifedipine oxidation (mean IC50 1.54-6.43 µg/mL). Clinical relevance of the inhibitory potential of DM, PC and PI is of concern for the further development of these plants for the treatment of malaria and/or cholangiocarcinoma.

Nuclear Receptors in Drug Metabolism, Drug Response and Drug Interactions

Orally delivered small-molecule therapeutics are metabolized in the liver and intestine by phase I and phase II drug-metabolizing enzymes (DMEs), and transport proteins coordinate drug influx (phase 0) and drug/drug-metabolite efflux (phase III). Genes involved in drug metabolism and disposition are induced by xenobiotic-activated nuclear receptors (NRs), i.e. PXR (pregnane X receptor) and CAR (constitutive androstane receptor), and by the 1α, 25-dihydroxy vitamin D3-activated vitamin D receptor (VDR), due to transactivation of xenobiotic-response elements (XREs) present in phase 0-III genes. Additional NRs, like HNF4-α, FXR, LXR-α play important roles in drug metabolism in certain settings, such as in relation to cholesterol and bile acid metabolism. The phase I enzymes CYP3A4/A5, CYP2D6, CYP2B6, CYP2C9, CYP2C19, CYP1A2, CYP2C8, CYP2A6, CYP2J2, and CYP2E1 metabolize >90% of all prescription drugs, and phase II conjugation of hydrophilic functional groups (with/without phase I modification) facilitates drug clearance. The conjugation step is mediated by broad-specificity transferases like UGTs, SULTs, GSTs. This review delves into our current understanding of PXR/CAR/VDR-mediated regulation of DME and transporter expression, as well as effects of single nucleotide polymorphism (SNP) and epigenome (specified by promoter methylation, histone modification, microRNAs, long non coding RNAs) on the expression of PXR/CAR/VDR and phase 0-III mediators, and their impacts on variable drug response. Therapeutic agents that target epigenetic regulation and the molecular basis and consequences (overdosing, underdosing, or beneficial outcome) of drug-drug/drug-food/drug-herb interactions are also discussed. Precision medicine requires understanding of a drug's impact on DME and transporter activity and their NR-regulated expression in order to achieve optimal drug efficacy without adverse drug reactions. In future drug screening, new tools such as humanized mouse models and microfluidic organs-on-chips, which mimic the physiology of a multicellular environment, will likely replace the current cell-based workflow.

Modulation of the pharmacokinetics, therapeutic and adverse effects of NSAIDs by Chinese herbal medicines

INTRODUCTION

Concomitant use of NSAIDs and Chinese herbal medicines (CHMs) is frequent, yet summarized information on their interactions is lacking.

AREAS COVERED

A systematic review of literature in four evidence-based English databases was performed. Articles which reported CHMs altering the pharmacokinetics, therapeutic and adverse effects of NSAIDs were identified and summarized. Such interactions may lead to beneficial, detrimental or no change in outcomes. The current review covers four therapeutic effects of NSAIDs, including: i) anti-inflammatory; ii) analgesic; iii) antiplatelet, cardiovascular and cerebrovascular; and iv) anticancer effects and four adverse effects of NSAIDs, including: i) gastrointestinal ulcer; ii) nephrotoxicity; iii) hepatotoxicity; and iv) antiplatelet effects and bleeding.

EXPERT OPINION

While majority of CHMs demonstrated effectiveness in alleviating NSAIDs-induced adverse effects and potentiating the therapeutic effects, this review provides insights for development of CHMs as add-on medications to NSAIDs therapies. However, since limited information was from well-designed clinical trials, the findings are not yet conclusive and more clinical studies are warranted to provide guidance for healthcare professionals. In future, researches on interactions between NSAIDs and CHMs are expected to grow and modern approaches such as pharmacogenomics might enhance the throughput and accuracy of identifying clinically relevant interactions.

Herbal medicines in Brazil: pharmacokinetic profile and potential herb-drug interactions

A plethora of active compounds found in herbal medicines can serve as substrate for enzymes involved in the metabolism of xenobiotics. When a medicinal plant is co-administered with a conventional drug and little or no information is known about the pharmacokinetics of the plant metabolites, there is an increased risk of potential herb-drug interactions. Moreover, genetic polymorphisms in a population may act to predispose individuals to adverse reactions. The use of herbal medicines is rapidly increasing in many countries, particularly Brazil where the vast biodiversity is a potential source of new and more affordable treatments for numerous conditions. Accordingly, the Brazilian Unified Public Health System (SUS) produced a list of 71 plant species of interest, which could be made available to the population in the near future. Physicians at SUS prescribe a number of essential drugs and should herbal medicines be added to this system the chance of herb-drug interactions further increases. A review of the effects of these medicinal plants on Phase 1 and Phase 2 metabolic mechanisms and the transporter P-glycoprotein was conducted. The results have shown that approximately half of these medicinal plants lack any pharmacokinetic data. Moreover, most of the studies carried out are in vitro. Only a few reports on herb-drug interactions with essential drugs prescribed by SUS were found, suggesting that very little attention is being given to the safety of herbal medicines. Here we have taken this information to discuss the potential interactions between herbal medicines and essential drugs prescribed to Brazilian patients whilst taking into account the most common polymorphisms present in the Brazilian population. A number of theoretical interactions are pinpointed but more pharmacokinetic studies and pharmacovigilance data are needed to ascertain their clinical significance.

The effect of complementary and alternative medicines on CYP3A4-mediated metabolism of three different substrates: 7-benzyloxy-4-trifluoromethyl-coumarin, midazolam and docetaxel

OBJECTIVE

Concomitant use of complementary and alternative medicine (CAM) and anticancer drugs can affect the pharmacokinetics of anticancer drugs by inhibiting the metabolizing enzyme cytochrome P450 3A4 (CYP3A4) (EC 1.14.13.157). Several in vitro studies determined whether CAM can inhibit CYP3A4, but these studies revealed contradictory results. A plausible explanation for these conflicting results is the use only of a single model CYP3A4 substrate in each study. Therefore, the objective was to determine the potential of selected CAM (β-carotene, Echinacea, garlic, Ginkgo biloba, ginseng, grape seed extract, green tea extract, milk thistle, saw palmetto, valerian, vitamin B6, B12 and C) to inhibit CYP3A4-mediated metabolism of different substrates: 7-benzyloxy-4-trifluoromethyl-coumarin (BFC), midazolam and docetaxel. The effect of CAM on CYP3A4-mediated metabolism of an anticancer drug has never been determined before in vitro, which makes this study unique. The oncolytic CYP3A4 substrate docetaxel was used to establish the predictive value of the model substrates for pharmacokinetic interactions between CAM and anticancer drugs in vitro, and to more closely predict these interactions in vivo.

METHODS

The inhibition of CYP3A4-mediated metabolism of 7-benzyloxy-4-trifluoromethyl-coumarin (BFC) by CAM was assessed in Supersomes, using the fluorometric CYP3A4 inhibition assay. In human liver microsomes (HLM) the inhibition of CYP3A4-mediated metabolism of midazolam and docetaxel was determined, using liquid-chromatography coupled to tandem mass spectrometry (LC-MS/MS).

KEY FINDINGS

The results confirmed grape seed and green tea as potent inhibitors and milk thistle as moderate inhibitor of CYP3A4-mediated metabolism of BFC, midazolam and docetaxel.

CONCLUSION

Clinical studies are required to determine the clinical relevance of the determined CYP3A4 inhibition by grape seed, green tea and milk thistle.

Cytochrome P450 enzyme mediated herbal drug interactions (Part 1)

It is well recognized that herbal supplements or herbal medicines are now commonly used. As many patients taking prescription medications are concomitantly using herbal supplements, there is considerable risk for adverse herbal drug interactions. Such interactions can enhance the risk for an individual patient, especially with regard to drugs with a narrow therapeutic index such as warfarin, cyclosporine A and digoxin. Herbal drug interactions can alter pharmacokinetic or/and pharmacodynamic properties of administered drugs. The most common pharmacokinetic interactions usually involve either the inhibition or induction of the metabolism of drugs catalyzed by the important enzymes, cytochrome P450 (CYP). The aim of the present article is to provide an updated review of clinically relevant metabolic CYP-mediated drug interactions between selected herbal supplements and prescription drugs. The commonly used herbal supplements selected include Echinacea, Ginkgo biloba, garlic, St. John's wort, goldenseal, and milk thistle. To date, several significant herbal drug interactions have their origins in the alteration of CYP enzyme activity by various phytochemicals. Numerous herbal drug interactions have been reported. Although the significance of many interactions is uncertain but several interactions, especially those with St. John's wort, may have critical clinical consequences. St. John's wort is a source of hyperforin, an active ingredient that has a strong affinity for the pregnane xenobiotic receptor (PXR). As a PXR ligand, hyperforin promotes expression of CYP3A4 enzymes in the small intestine and liver. This in turn causes induction of CYP3A4 and can reduce the oral bioavailability of many drugs making them less effective. The available evidence indicates that, at commonly recommended doses, other selected herbs including Echinacea, Ginkgo biloba, garlic, goldenseal and milk thistle do not act as potent or moderate inhibitors or inducers of CYP enzymes. A good knowledge of the mechanisms of herbal drug interactions is necessary for assessing and minimizing clinical risks. These processes help prediction of interactions between herbal supplements and prescription drugs. Healthcare professionals should remain vigilant for potential interactions between herbal supplements/medicines and prescription drugs, especially for drugs with a narrow therapeutic index are used.

Relevance of in vitro and clinical data for predicting CYP3A4-mediated herb-drug interactions in cancer patients

The use of complementary and alternative medicines (CAM) by cancer patients is increasing. Concomitant use of CAM and anticancer drugs could lead to serious safety issues in patients. CAM have the potential to cause pharmacokinetic interactions with anticancer drugs, leading to either increased or decreased plasma levels of anticancer drugs. This could result in unexpected toxicities or a reduced efficacy. Significant pharmacokinetic interactions have already been shown between St. John's Wort (SJW) and the anticancer drugs imatinib and irinotecan. Most pharmacokinetic CAM-drug interactions, involve drug metabolizing cytochrome P450 (CYP) enzymes, in particular CYP3A4. The effect of CAM on CYP3A4 activity and expression can be assessed in vitro. However, no data have been reported yet regarding the relevance of these in vitro data for the prediction of CAM-anticancer drug interactions in clinical practice. To address this issue, a literature research was performed to evaluate the relevance of in vitro data to predict clinical effects of CAM frequently used by cancer patients: SJW, milk thistle, garlic and Panax ginseng (P. ginseng). Furthermore, in clinical studies the sensitive CYP3A4 substrate probe midazolam is often used to determine pharmacokinetic interactions. Results of these clinical studies with midazolam are used to predict pharmacokinetic interactions with other drugs metabolized by CYP3A4. Therefore, this review also explored whether clinical trials with midazolam are useful to predict clinical pharmacokinetic CAM-anticancer drug interactions. In vitro data of SJW have shown CYP3A4 inhibition after short-term exposure and induction after long-term exposure. In clinical studies using midazolam or anticancer drugs (irinotecan and imatinib) as known CYP3A4 substrates in combination with SJW, decreased plasma levels of these drugs were observed, which was expected as a consequence of CYP3A4 induction. For garlic, no effect on CYP3A4 has been shown in vitro and also in clinical studies garlic did not affect the pharmacokinetics of both midazolam and docetaxel. Milk thistle and P. ginseng predominantly showed CYP3A4 inhibition in vitro. However, in clinical studies these CAM did not cause significant pharmacokinetic interactions with midazolam, irinotecan, docetaxel and imatinib. Most likely, factors as poor pharmaceutical availability, solubility and bioavailability contribute to the lack of significant clinical interactions. In conclusion, in vitro data are useful as a first indication for potential pharmacokinetic drug interactions with CAM. However, the discrepancies between in vitro and clinical results for milk thistle and P. ginseng show that clinical studies are required for confirmation of potential interactions. At last, midazolam as a model substrate for CYP3A4, has convincingly shown to correctly predict clinical interactions between CAM and anticancer drugs.

The effect of garlic supplements and phytochemicals on the ADMET properties of drugs

INTRODUCTION

Garlic supplements have received wide public attention because of their health-beneficial effects. Although these products are considered as innocuous, several case reports and studies have shown the capacity of individual garlic phytochemicals/supplements to interfere with drug pharmacokinetics.

AREAS COVERED

This review covers recently published literature on garlic chemistry and composition, and provides a thorough review of published studies evaluating drug-garlic interactions. The authors illustrate the mechanisms underlying pharmacokinetic interactions, which could serve as important highlights in further research to explain results for drugs with narrow therapeutic indices or for drugs, utilizing multiple absorption, distribution and metabolism pathways.

EXPERT OPINION

To increase the relevance of further research on safety and efficacy of garlic supplements and phytochemicals, their composition should be addressed before conducting in vitro or in vivo research. It is also strongly recommended to characterize in vitro formulation performance to assess the rate and extent of garlic phytochemical release in order to anticipate the in vivo impact on the pharmacokinetics of concomitantly consumed drugs. The main conclusion of this review is that the impact of garlic on different stages of pharmacokinetics, especially on drug absorption and metabolism, is drug specific and dependent on the type/quality of utilized supplement.