In vitro interactions between aged garlic extract and drugs used for the treatment of cardiovascular and diabetic patients

Cardiovascular Effects of Herbal Products and Their Interaction with Antihypertensive Drugs-Comprehensive Review

Hypertension is a highly prevalent population-level disease that represents an important risk factor for several cardiovascular complications and occupies a leading position in mortality statistics. Antihypertensive therapy includes a wide variety of drugs. Additionally, the potential antihypertensive and cardioprotective effects of several phytotherapy products have been evaluated, as these could also be a valuable therapeutic option for the prevention, improvement or treatment of hypertension and its complications. The present review includes an evaluation of the cardioprotective and antihypertensive effects of garlic, Aloe vera, green tea, Ginkgo biloba, berberine, ginseng, Nigella sativa, Apium graveolens, thyme, cinnamon and ginger, and their possible interactions with antihypertensive drugs. A literature search was undertaken via the PubMed, Google Scholar, Embase and Cochrane databases. Research articles, systematic reviews and meta-analyses published between 2010 and 2023, in the English, Hungarian, and Romanian languages were selected.

Pharmacokinetic Interactions between Herbal Medicines and Drugs: Their Mechanisms and Clinical Relevance

The therapeutic efficacy of a drug or its unexpected unwanted side effects may depend on the concurrent use of a medicinal plant. In particular, constituents in the medicinal plant extracts may influence drug bioavailability, metabolism and half-life, leading to drug toxicity or failure to obtain a therapeutic response. This narrative review focuses on clinical studies improving knowledge on the ability of selected herbal medicines to influence the pharmacokinetics of co-administered drugs. Moreover, in vitro studies are useful to anticipate potential herbal medicine-drug interactions. In particular, they help to elucidate the cellular target (metabolic or transporter protein) and the mechanism (induction or inhibition) by which a single constituent of the herbal medicine acts. The authors highlight the difficulties in predicting herbal–drug interactions from in vitro data where high concentrations of extracts or their constituents are used and pharmacokinetics are missed. Moreover, the difficulty to compare results from human studies where different kinds of herbal extracts are used is discussed. The herbal medicines discussed are among the best sellers and they are reported in the “Herbal Medicines for Human Use” section of the European Medicinal Agency (EMA).

Efflux and uptake transporters involved in the disposition of bazedoxifene

Bazedoxifene, a novel selective estrogen receptor modulator, has complex pharmacokinetics with rapid absorption, high metabolic clearance, low oral bioavailability (6.25 %) and a slow elimination phase. Our hypothesis is that drug uptake and efflux transporters may play an important role in its disposition. To adequately cover all aspects of bazedoxifene transport, several approaches were undertaken: PAMPA assay, ATPase assay, membrane inside-out vesicles and Caco-2 and CHO cell lines. The results obtained from PAMPA experiments showed moderate passive permeability of bazedoxifene (P app ≈ 2 × 10(-6)cm/s), suggesting the existence of an active transport during the rapid absorption phase. The Caco-2 transport assay showed large and significant changes in the measured efflux ratios of bazedoxifene when selective transporter inhibitors were applied: verapamil (a Pgp inhibitor), MK571 (an MRP inhibitor), Ko143 (a BCRP inhibitor) and DIDS (an OATP inhibitor). Additionally, membrane preparation experiments demonstrated the interaction of bazedoxifene with P-gp, MRP2 and BCRP. CHO experiments did not show any interactions of bazedoxifene with OATP1B1 or OATP1B3; therefore, bazedoxifene may be a substrate of other OATP isoform(s). The comprehensive in vitro study indicates a strong involvement of Pgp, MRP, BCRP and OATP in bazedoxifene disposition.

Enhanced absorption and bioavailability of hydrochlorothiazide by Chinese medicines in the Zhenju antihypertensive compound

OBJECTIVES

This study was performed to investigate the influence of traditional Chinese medicines in the Zhenju antihypertensive compound (ZJAHC) on the oral absorption of hydrochlorothiazide (HCT) both in vitro and in vivo.

METHODS

Caco-2 cells and the in situ closed loop system were used to investigate the possible mechanism of the Chinese-Western medicine interaction on the transepithelial transport and uptake of HCT. The influence of TCMs on the pharmacokinetics and bioavailability of HCT was also studied to reveal the possible interaction in vivo.

KEY FINDINGS

In an in situ intestinal perfusion study, the cumulative amount of HCT of ZJAHC group (506.05 μg ± 96.03) was 2.2-fold, 2.18-fold and 1.38-fold higher compared to that of the HCT group (228.29 μg ± 23.39), HCT-clonidine (CLO) group (232.13 ± 54.79 μg) and HCT-rutin (RT) group (366.08 ± 21.97 μg), respectively, after 120 min of perfusion. A pharmacokinetic analysis showed a significant increase in area under the plasma concentration-time curve (AUC) of HCT in the ZJAHC group by 2.14-fold, 2.01-fold and 1.32-fold compared to the HCT, HCT-CLO and HCT-RT groups, respectively. As a P-gp inhibitor, RT could contribute to the enhanced oral absorption of HCT in ZJAHC.

CONCLUSION

The combination of traditional Chinese medicines and chemical drugs may provide a promising strategy and unique advantages to reduce the dosage and side effects of chemical drugs while maintaining an effect on hypertension.

Influence of hepatic and intestinal efflux transporters and their genetic variants on the pharmacokinetics and pharmacodynamics of raloxifene in osteoporosis treatment

Raloxifene exhibits a large and unexplained interindividual variability in its pharmacokinetics and pharmacodynamics. The aim of our study was to identify transporters involved in the efflux of raloxifene and its glucuronide metabolites by various in vitro models and by an in vivo study to explore the possible involvement of P-glycoprotein (Pgp), multidrug resistance-associated protein (MRP)1, MRP2, MRP3, and breast cancer resistance protein in the observed high interindividual variability. Experiments with the parallel artificial membrane permeability assay showed the highest passive permeability for raloxifene, followed by raloxifene-6-β-glucuronide (M1), raloxifene-4'-β-glucuronide (M2), and raloxifene-6,4'-diglucuronide (M3). Caco-2 cell monolayer experiments indicated an interaction of raloxifene with Pgp. The ATPase assay confirmed the raloxifene interaction with Pgp and indicated interactions of all raloxifene species with MRP1, MRP2, MRP3, and breast cancer resistance protein, except for M1, which did not show any interactions with MRP2. Furthermore, the vesicular experiments confirmed the interaction of M2 and M3 with MRP2. Although the in vivo study on osteoporotic postmenopausal women on raloxifene could not confirm a significant influence of ABCB1 and ABCC2 genetic polymorphisms on its pharmacokinetics, a clear trend toward higher total raloxifene concentrations was observed in carriers of at least 1 ABCB1 c.3435T allele. Moreover, the same polymorphism effect was also observed as a significant increase in total hip bone mineral density after 1 year of treatment. The results of our study support the involvement of efflux transporters in disposition of raloxifene and its metabolites and may partially explain the observed raloxifene variability by the influence of the ABCB1 c.3435C>T polymorphism.

Unique vascular protective properties of natural products: supplements or future main-line drugs with significant anti-atherosclerotic potential?

Natural health products (NHP) which include minerals, vitamins and herbal remedies are not generally considered by medical practitioners as conventional medicines and as such are not frequently prescribed by health centre's as either main-line or supplemental treatments. In the field of cardiovascular medicine, studies have shown that typically, less than half of patients suffering from coronary syndromes chose to take any form of NHP supplement and these products are rarely recommended by their medical practitioner. Vascular/endothelial cell damage is a key instigator of coronary arterial plaque development which often culminates in thrombosis and myocardial infarction (MI). Current treatment for patients known to be at risk of primary or secondary (MI) includes lipid lowering statins, anti-clotting agents (e.g. tissue plasminogen activator; tPA) and drugs for stabilization of blood pressure such as beta-blockers. However, evidence has been building which suggests that components of at least several NHP (e.g. aged garlic extract (AGExt), resveratrol and green tea extracts (GTE)) may have significant vascular protective effects through reduction of oxidative stress, lowering of blood pressure, reduction in platelet aggregation, vasodilation and inhibition of abnormal angiogenesis. Therefore, in this review we will discuss in detail the potential of these substances (chosen on the basis of their potency and complimentarity) as anti-atherosclerotic agents and the justification for their consideration as main-line additional supplements or prescriptions.

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.

Drug-permeability and transporter assays in Caco-2 and MDCK cell lines

The human colon adenocarcinoma Caco-2 and Madin–Darby canine kidney epithelial cell lines provide in vitro tools to assess a drug’s permeability and transporter interactions during discovery and development. The cells, when cultured on semiporous filters, form confluent monolayers that model the intestinal epithelial barrier for permeability, transporter and drug-interaction assays. The applications of these assays in pharmaceutical research include qualitative prediction and ranking of absorption, determining mechanism(s) of permeability, formulation effects on drug permeability, and the potential for transporter-mediated drug–drug interactions. This review focuses on recent examples of Caco-2 and Madin–Darby canine kidney cells assays for drug permeability including transfected and knock-down cells, miniaturization and automation, and assay combinations to better understand and predict intestinal drug absorption.

HIV protease inhibitors: garlic supplements and first-pass intestinal metabolism impact on the therapeutic efficacy

BACKGROUND/AIMS

The aim of this study was to elucidate the impact of first-pass intestinal metabolism to therapeutic efficacy of antiretrovirals and to ascertain interaction mechanisms between garlic supplements (aged garlic extract) and HIV-protease inhibitors.

METHODS

In vitro permeability through rat jejunum, Caco-2 cell monolayers was determined and CYP3A4 metabolism studies were performed.

RESULTS

Saquinavir and darunavir efflux from enterocytes into gastrointestinal lumen significantly increased in the presence of aged garlic extract, whereas their CYP3A4 metabolism was inhibited. In the case of saquinavir a significant increase of its efflux was observed also in the presence of lower ritonavir doses. Because both drugs bound to different binding sites on P-glycoprotein and/or multidrug resistance associated protein 2 than garlic phytochemicals or ritonavir, lower amounts of antiretrovirals were absorbed.

CONCLUSIONS

The fractions of tested anti-HIV drugs absorbed could decrease significantly during self-medication with garlic supplements or ritonavir dose adjustments. Due to distinct saquinavir and darunavir preferences for binding sites on efflux transporters, the presence of other compounds (garlic phytochemicals, ritonavir), capable of influencing intestinal transporter-enzyme interplay, might lead to pharmacokinetic interactions observed in clinical studies and case reports with anti-HIV drugs.

Garlic flavonoids and organosulfur compounds: impact on the hepatic pharmacokinetics of saquinavir and darunavir

The therapeutic efficacy of saquinavir and darunavir is affected by the presence of xenobiotics (such as garlic compounds) capable of modifying transporter-enzyme interplay. To ascertain the mechanism of interactions between antiretroviral drugs and garlic supplements and to identify the garlic constituents responsible, the hepatic pharmacokinetics of two antiretroviral drugs was investigated in the presence of garlic phytochemicals and aged garlic extract. For this purpose, rat liver slices and isolated rat hepatocytes were used. Aged garlic extract significantly inhibited saquinavir efflux from rat hepatocytes, while the efflux of darunavir significantly increased. Phytochemicals inducing distribution changes of saquinavir and darunavir were most probably flavonoids and lipophilic organosulfur compounds, respectively. All tested phytochemicals (except S-allyl L-cysteine) and aged garlic extract inhibited CYP3A4 metabolism of both drugs and modulated hepatic distribution of the corresponding saquinavir and darunavir metabolites. The competition between saquinavir and garlic constituent(s) for the same binding site on the efflux transporter and the positive cooperative effect between darunavir and garlic phytochemical(s), which bind to separate binding places on transporter, are the most probable mechanisms explaining the plasma profile changes, which could occur in vivo during concomitant consumption of antiretrovirals and garlic supplements.