Influence of dietary components on the gastrointestinal metabolism and transport of drugs

Healthcare Professionals' Knowledge and Behaviors Regarding Drug-Dietary Supplement and Drug-Herbal Product Interactions

Given the widespread use of dietary supplements (DS) and herbal products (HP), healthcare professionals (HCPs) will increasingly encounter patients who use these preparations with conventional drugs and who need their services to reduce the consequences of adverse therapeutic outcomes. The aim of our survey was to assess the knowledge and behaviors of HCPs regarding the risk of potential drug−dietary supplement (DDSIs) and drug−herbal product (DHPIs) interactions. This cross-sectional survey collected data via on paper-based questionnaire among general practitioners (GPs) (n = 105), specialty doctors (n = 87) and nurses (n = 154). The HCPs were mostly familiar with the interaction of doxycycline with magnesium (83%) and were least familiar with interaction of warfarin with glucosamine (14%). The results on DDSIs and DHPIs knowledge showed that GPs scored significantly higher than nurses (p < 0.001 and p = 0.003, respectively), while specialty doctors scored significantly higher than nurses only on DDSIs knowledge (p < 0.001). Only 28% of respondents reported that they often or always ask patients on drug therapy about the use of DS or HP, and 25% of respondents record such data in the medical documentation of patients. Our results showed that HCPs have sufficient knowledge about most major DDSIs and DHPIs, but insufficient knowledge about most moderate interactions. However, their overall knowledge and behavior regarding the risk of these interactions indicate the need for further continuing education and training.

Implication of metabolomics and transporter modulation based strategies to minimize multidrug resistance and enhance site-specific bioavailability: a needful consideration toward modern anticancer drug discovery

Induction of drug-metabolizing enzymes and efflux transporters (DMET) through activation of pregnane x receptor (PXR) is the primary factor involved in almost all bioavailability and drug resistance-related problems of anticancer drugs. PXR is a transcriptional regulator of many metabolizing enzymes and efflux transporters proteins like p-glycoprotein (p-gp), multidrug resistant protein 1 and 2 (MRP 1 and 2), and breast cancer resistant protein (BCRP), etc. Several anticancer drugs are potent activators of PXR receptors and can modulate the gene expression of DMET proteins. Involvement of anticancer drugs in transcriptional regulation of DMET can prompt increased metabolism and efflux of their own or other co-administered drugs, which leads to poor site-specific bioavailability and increased drug resistance. In this review, we have discussed several novel strategies to evade drug-induced PXR activation and p-gp efflux including assessment of PXR ligand and p-gp substrate at early stages of drug discovery. Additionally, we have critically discussed the chemical structure and drug delivery-based approaches to avoid PXR binding and inhibit the p-gp activity of the drugs at their target sites.

Effect of piperine and quercetin alone or in combination with marbofloxacin on CYP3A37 and MDR1 mRNA expression levels in broiler chickens

After oral route of administration, drug absorption is unpredictable and is governed by various factors such as multi drug resistance-1 (MDR1) an efflux transporter and drug metabolizing enzymes (like CYP3A4, CYP3A37, CYP2D6) at intestine and liver. Naturally available phyto chemicals like piperine and quercetin as well as some floroquinolones are known to inhibit MDR1 and CYP3A37 activity and increases bioavailability of co-administered drugs. This study was carried out to investigate the effect of piperine and quercetin alone or in combination with marbofloxacin on CYP3A37 and MDR1 mRNA expression levels in liver and intestine of broiler chicken. After oral administration of piperine and quercetin for 3 consecutive days followed by with or without oral administration of marbofloxacin for 5 days, CYP3A37 and MDR1 mRNA expression levels were determined using quantitative real-time PCR. Total of 36 broiler chickens in seven individual groups were treated with different regimen and the mRNA expression levels at duodenum and liver were analyzed with apt statistical tools. After piperine and quercetin combined treatment with marbofloxacin, CYP3A37 mRNA expression levels were significantly down regulated by 20.57 (p = .034) and 25.95 (p = .003) folds; and MDR1 mRNA expression levels were also significantly down regulated by 11.33 (p = .012) and 33.59 (p = .006) folds in liver and duodenum, respectively. Down regulation of CYP3A37 and MDR1 mRNA in liver and duodenum indicate the combined pretreatment of piperine and quercetin may be useful for improving the pharmacokinetics of orally administered drugs which are substrates for CYP3A37 and MDR1.

Bioavailability Enhancement of Poorly Soluble Drugs: The Holy Grail in Pharma Industry

Background:

Bioavailability, one of the prime pharmacokinetic properties of a drug, is defined as the fraction of an administered dose of unchanged drug that reaches the systemic circulation and is used to describe the systemic availability of a drug. Bioavailability assessment is imperative in order to demonstrate whether the drug attains the desirable systemic exposure for effective therapy. In recent years, bioavailability has become the subject of importance in drug discovery and development studies.

Methods:

A systematic literature review in the field of bioavailability and the approaches towards its enhancement have been comprehensively done, purely focusing upon recent papers. The data mining was performed using databases like PubMed, Science Direct and general Google searches and the collected data was exhaustively studied and summarized in a generalized manner.

Results:

The main prospect of this review was to generate a comprehensive one-stop summary of the numerous available approaches and their pharmaceutical applications in improving the stability concerns, physicochemical and mechanical properties of the poorly water-soluble drugs which directly or indirectly augment their bioavailability.

Conclusion:

The use of novel methods, including but not limited to, nano-based formulations, bio-enhancers, solid dispersions, lipid-and polymer-based formulations which provide a wide range of applications not only increases the solubility and permeability of the poorly bioavailable drugs but also improves their stability, and targeting efficacy. Although, these methods have drastically changed the pharmaceutical industry demand for the newer potential methods with better outcomes in the field of pharmaceutical science to formulate various dosage forms with adequate systemic availability and improved patient compliance, further research is required.

A Multidisciplinary Review of Nutrition Considerations in the Pediatric Oncology Population: A Perspective From Children's Oncology Group

Over the past few decades, great progress has been made in the survival rates of childhood cancer. As survival rates have improved, there has been an increased focus on supportive care. Nutrition is a supportive-care modality that has been associated with improved tolerance to chemotherapy, improved survival, increased quality of life, and decreased risk of infection in children undergoing anticancer therapy. Guidelines and assessment criteria have been proposed for the nutrition management of a child with cancer; however, there is no consistent use of criteria among institutions treating children with cancer. This review will present the current evidence and standards of practice incorporating aspects of nutrition, nursing, pharmacology, and psychosocial challenges to consider in the nutrition management of a child with cancer. Recommendations for clinical practice are presented.

Administration of Piceatannol Complexed with α-Cyclodextrin Improves Its Absorption in Rats

Piceatannol is polyphenolic antioxidant found in passion fruit (Passiflora edulis) seeds. The aim of this study was to improve the absorption of piceatannol using α-cyclodextrin (αCD). The solubility of piceatannol in neutral and acidic solutions increased in an αCD concentration-dependent manner. The maximum plasma concentration of intact piceatannol and the time-to-maximum plasma concentration of O-methylated piceatannol metabolites increased in rats administered αCD-piceatannol inclusion complexes (PICs). Administering the αCD inclusion complexes significantly increased the area under the concentration-time curve of total stilbene derivatives (0-3 h) in terms of the total amount of intact piceatannol, O-methylated piceatannol, conjugated piceatannol, and isorhapontigenin. Gastrointestinal ligation experiments demonstrated that substantially higher levels of piceatannol metabolites were present in the lower intestine (the ileum) at 1 h postintragastric αCD-PICs administration as compared to those observed following piceatannol administration only. These results suggested that αCD enhanced piceatannol movement and absorption in the small intestine.

In vitro effects of standardized extract of Bacopa monniera and its five individual active constituents on human P-glycoprotein activity

1. For centuries Bacopa monniera (BM) has been used as an herbal drug for the treatment of various mental ailments. A chemically standardized alcoholic extract of BM is clinically available over the counter herbal remedy for memory enhancement in children and adults. Consumption of herbal preparations has been reported to alter the function of membrane transporters, especially P-glycoprotein (P-gp), ATP-dependent drug efflux transporter responsible for the development of herb-drug interactions. 2. In the present study, we evaluated the in vitro effect of BM extract and its five individual active constituents (namely, bacopaside I, bacopaside II and bacopasaponin C, bacoside A and bacoside A3) on P-gp function using luminescent P-gp ATPase assay and Rh123 transport assay across human MDR1 gene transfected LLC-GA5-COL150 cell line. 3. It was observed that BM extract and its five individual constituents inhibited both basal activity as well as verapamil-stimulated ATPase activity, suggesting their affinity towards P-gp. Further, BM and its five active constituents inhibited the rhodamine 123 (Rh123) transport across LLC-GA5-COL150 cell monolayer with bacopaside II being the most potent inhibitor of P-gp, which decreased P-gp efflux ratio of Rh123 by fourfold in comparison to control. 4. Our finding may prove beneficial in predicting the potential herb-drug interactions of BM on concomitant medication with P-gp substrate drugs in clinical settings.

Effects of food and gender on the pharmacokinetics of ginkgolides A, B, C and bilobalide in rats after oral dosing with ginkgo terpene lactones extract

The ginkgo terpene lactones (GTL), mainly including bilobalide (BB), ginkgolide A (GA), ginkgolide B (GB) and ginkgolide C (GC) possess different biological activities such as peripheral vasoregulation, platelet-activating factor (PAF) receptor antagonism, neuroprotective properties and prevention of membrane damage caused by free radicals. To investigate the effects of food and gender on the bioavailability of BB, GA, GB and GC after oral administration of GTL extract, a rapid UPLC-MS/MS method was developed and validated. A reversed phase C18 column (100mm×2.1mm, i.d., 1.7μm) and a mobile phase consisted of methanol and 1mM ammonium acetate (70/30, v/v) were employed. Compared with the fasted group, the t1/2 values for BB, GA, GB and GC in fed were all increased (p<0.05), AUC0-t and AUC0-∞ values of BB, GA, GB and GC were all significantly increased (p<0.05), but the Cmax values of BB, GA, GB and GC were significantly decreased (p<0.05). In comparison with the male group, all of the t1/2 values and AUC0-t values for BB, GA, GB and GC in female were higher (p<0.05), but no statistical difference in Tmax values for BB, GA, GB and GC between these two groups. Food and gender factor showed significant effects on the pharmacokinetics of BB, GA, GB, and GC. The results suggested that oral doses of GTL should be lowered for fasted and female subjects, compared with the fed and male subjects, respectively.

The effect of piperine on midazolam plasma concentration in healthy volunteers, a research on the CYP3A-involving metabolism

Some studies showed that piperine (the alkaloid of piper nigrum) can change the activities of microsomal enzymes. Midazolam concentration is applied as a probe to determine the CYP3A enzyme activity. This study was done to determine piperine pretreatment role on midazolam plasma concentration.Twenty healthy volunteers (14 men and 6 women) received oral dose of piperine (15 mg) or placebo for three days as pretreatment and midazolam (10 mg) on fourth day of study and the blood samples were taken at 0.5, 2.5 and 5 h after midazolam administration. The midazolam plasma levels were assayed using HPLC method (C18 analytical column, 75:25 methanol:water as mobile phase, UV detector at 242 nm wavelength and diazepam as internal standard). Data were fit in a "one-compartment PK model" using P-Pharm 1.5 software and analyzed under statistical tests.The mean ±SD of the age and body mass index were 24.3 ± 1.83 years (range: 21-28 years) and 23.46± 2.85, respectively. The duration of sedation in piperine receiving group was greater that the placebo group (188±59 vs. 102±43 min, p<0.0001). Half-life and clearance of midazolam were higher in piperine pretreatment group compared to placebo [1.88±0.03 vs. 1.71± 0.04 h (p<0.0001) and 33.62 ± 0.4 vs. 37.09 ± 1.07 ml/min (p<0.0001), respectively].According to the results, piperine can significantly increases half-life and decreases clearance of midazolam compared to placebo. It is suggested that piperine can demonstrate those effects by inhibition CYP3A4 enzyme activity in liver microsomal system.

Development and in vivo evaluation of an oral vitamin B12 delivery system

Recently, poly(acrylic acid)-cysteine (PAA-cys) based formulations have shown to modulate vitamin B12 absorption across Caco-2 cells monolayers and rat intestinal mucosa. The aim of the present study was to provide a proof-of-principle for a delivery system based on PAA-cys in vivo by administering vitamin B12 to Sprague Dawley rats. In vitro, the permeation enhancing effect of unmodified and thiolated PAA was evaluated using rat intestinal mucosa mounted on Ussing type chambers and was compared to that of verapamil and reduced glutathione (GSH). Vitamin B12 transport in the presence of 0.5% (m/v) PAA-cys was 3.96-fold improved compared to buffer, while 91.5% and 56.5% increased compared to verapamil and GSH, respectively. In vivo, the oral administration of minitablets based on 0.5mg vitamin B12 with 4.5mg PAA or PAA-cys resulted in a significant improvement of vitamin B12 absolute bioavailability. The area under the serum concentration-time curve (AUC₀₋₈) of vitamin B12 after administration of PAA and PAA-cys minitablets was 1.74-fold and 2.92-fold higher in comparison with oral solution, respectively. Thiolated formulations provided an absolute bioavailability of 0.89%. According to the achieved results, PAA-cys can be considered a valuable tool for improving the oral bioavailability of vitamin B12.

Interaction profile of Zizyphus jujuba with phenytoin, phenobarbitone, and carbamazepine in maximal electroshock-induced seizures in rats

The antiepileptic effect of hydroalcoholic extract of Zizyphus jujuba (HEZJ) in experimental seizures was demonstrated earlier. The present study aimed to evaluate the pharmacokinetic and pharmacodynamic interactions of HEZJ with phenytoin (PHT), phenobarbitone (PB), and carbamazepine (CBZ) in maximal electroshock (MES)-induced seizures in male Wistar rats. Maximal electroshock (70 mA, 9 ms pulse width, 0.2 s) was used to induce seizures. Blood samples were collected at two time points for estimation of serum PHT, PB, and CBZ levels using high-pressure liquid chromatography (HPLC). Co-administration of HEZJ with the sub-therapeutic doses of PHT, PB, and CBZ exhibited 66.7, 66.7, and 50.0% protection against tonic hind limb extension as compared to 33.3, 33.3, and 50% protection respectively, in the groups treated with PHT, PB, and CBZ alone in their sub-therapeutic doses. Co-administration of HEZJ with the sub-therapeutic doses of these antiepileptic drugs (AEDs) showed significant improvement in cognitive functions as compared to MES group as well as these AEDs alone. A significant increase in glutathione levels and decrease in malondialdehyde levels were observed with pretreatment of HEZJ with the sub-therapeutic doses of these AEDs. Co-administration of HEZJ with PHT, PB, and CBZ did not cause any significant changes in the serum concentrations of these AEDs. The results of the present study indicate that the co-administration of HEZJ with sub-therapeutic doses of PHT and PB potentiated the antiepileptic effect of PHT and PB in MES-induced seizures with no change found in the antiepileptic effect of CBZ.

Herb-drug interaction of 50 Chinese herbal medicines on CYP3A4 activity in vitro and in vivo

The purpose of this study is to evaluate the effects of Chinese herbal medicines on the enzymatic activity of CYP3A4 and the possible metabolism-based herb-drug interactions in human liver microsomes and in rats. Fifty single-herbal preparations were screened for the activity of CYP3A4 using human liver microsomes for an in vitro probe reaction study. The enzymatic activity of CYP3A4 was estimated by determing the 6β-hydroxytestosterone metabolized from testosterone performed on a liquid chromatography-tandem mass spectrometry (LC-MS/MS). Huang Qin (Scutellaria baicalensis Geprgi), Mu Dan Pi (Paeonia suffruticosa Andr.), Ji Shiee Terng (Spatholobus suberectus Dunn.) and Huang Qi (Astragalus membranaceus [Fisch] Bge) have been demonstrated to have remarkable inhibiting effects on the metabolism of CYP3A4, whereas Xi Yi Hua (Magnolia biondii Pamp.) exhibited a moderate inhibition. These five single herbs were further investigated in an animal study using midazolam. Mu Dan Pi, Ji Shiee Terng and Huang Qi were observed to have greatly increased in the C(max) and AUC of midazolam. This study provides evidence of possible herb-drug interactions involved with certain single herbs.

Co-administration of piperine and docetaxel results in improved anti-tumor efficacy via inhibition of CYP3A4 activity

BACKGROUND

Docetaxel is the mainline treatment approved by the FDA for castration-resistant prostate cancer (CRPC) yet its administration only increases median survival by 2-4 months. Docetaxel is metabolized in the liver by hepatic CYP3A4 activity. Piperine, a major plant alkaloid/amide, has been shown to inhibit the CYP3A4 enzymatic activity in a cell-free system. Thus, we investigated whether the co-administration of piperine and docetaxel could increase docetaxel's pharmacokinetic activity in vitro and in vivo.

METHODS

Liver CYP3A4 enzymatic activity was measured by fluorescence. In vivo docetaxel pharmacokinetic activity was analyzed by liquid chromatography. An in vivo xenograft model of human CRPC was utilized to assess the anti-tumor effect of docetaxel when co-administered with piperine.

RESULTS

Inhibition of hepatic CYP3A4 activity resulted in an increased area under the curve, half-life and maximum plasma concentration of docetaxel when compared to docetaxel alone administration. The synergistic administration of piperine and docetaxel significantly improved the anti-tumor efficacy of docetaxel in a xenograft model of human CRPC.

CONCLUSIONS

Docetaxel is one of the most widely used cytotoxic chemotherapeutic agents and is currently the mainstay treatment for metastatic CRPC. Dietary constituents are important agents modifying drug metabolism and transport. In our studies, dietary consumption of piperine increases the therapeutic efficacy of docetaxel in a xenograft model without inducing more adverse effects on the treated mice.

Antigenotoxic activity of naturally occurring furanocoumarins

This study was designed to investigate the antigenotoxic effects of a series of naturally occurring furanocoumarins (NOFs) including isoimperatorin, imperatorin, (+)-oxypeucedanin, (+)-byakangelicol, and (+)-byakangelicine on antigenotoxic activities against genotoxicity induced by carcinogens [furylfuramide and N-methyl-N'-nitro-N-nitrosoguanidine], and procarcinogens 2-[2-(acetylamino)-4-amino-5-methoxyphenyl]-5-amino-7-bromo-4-chloro-2H-benzotriazole (PBTA-4) and 2-amino-3,4-dimethyl-3H-imidazo-[4,5-f] quinoline (MeIQ)] to genotoxic metabolites catalyzed by rat S9 or rat and human recombinant cytochrome P450 (CYP) 1As by using the umu test based on SOS response. Five different NOFs, which were found in the human diets, strongly inhibited the umuC induction by procarcinogens, but did not be affected by carcinogens. Notably, isoimperatorin and (+)-byakangelicol were found to be potent inhibitors on the metabolic activation of PBTA-4 and MeIQ to genotoxic metabolites catalyzed by rat and human CYP1A1, or rat and human CYP1A2, respectively. In addition, to elucidate the mechanism of their antigenotoxic effects against procarcinogens, the effects of NOFs on rat and human CYP1A1- or rat and human CYP1A2-related enzyme activities of 7-ethoxyresorufin-O-deethylase (EROD) were also investigated. Reduction of the EROD activities by some of the NOFs with IC(50) values of 0.23-20.64 μM was found to be due to strong inhibition of CYP1A1 and CYP1A2 dependent monooxygenases. Furthermore, the mechanism of inhibitions by NOFs on human CYP1A1 and CYP1A2 was analyzed by means of Dixon plots plus Cornish-Bowden plots. The kinetic studies of inhibition types revealed that these compounds inhibited the human CYP1A1 and CYP1A2 a variety of modes rather than by a uniform one. Moreover, experiments with a two-stage incubation indicated that NOFs, except for imperatorin, inhibited human CYP1A1 in a mechanism-based manner, but directly inhibited human CYP1A2. This data suggest that certain NOFs, to which humans are exposed in the diet, may be capable of affecting the metabolic activation of procarcinogens due to inhibitions of CYP1A1 and CYP1A2 enzymes.

Intestinal lymphatic transport for drug delivery

Intestinal lymphatic transport has been shown to be an absorptive pathway following oral administration of lipids and an increasing number of lipophilic drugs, which once absorbed, diffuse across the intestinal enterocyte and while in transit associate with secretable enterocyte lipoproteins. The chylomicron-associated drug is then secreted from the enterocyte into the lymphatic circulation, rather than the portal circulation, thus avoiding the metabolically-active liver, but still ultimately returning to the systemic circulation. Because of this parallel and potentially alternative absorptive pathway, first-pass metabolism can be reduced while increasing lymphatic drug exposure, which opens the potential for novel therapeutic modalities and allows the implementation of lipid-based drug delivery systems. This review discusses the physiological features of the lymphatics, enterocyte uptake and metabolism, links between drug transport and lipid digestion/re-acylation, experimental model (in vivo, in vitro, and in silico) of lymphatic transport, and the design of lipid- or prodrug-based drug delivery systems for enhancing lymphatic drug transport.

Absorption, distribution, metabolism and excretion pharmacogenomics of drugs of abuse

Pharmacologic and toxic effects of xenobiotics, such as drugs of abuse, depend on the genotype and phenotype of an individual, and conversely on the isoenzymes involved in their metabolism and transport. The current knowledge of such isoenzymes of frequently abused therapeutics such as opioids (oxycodone, hydrocodone, methadone, fentanyl, buprenorphine, tramadol, heroin, morphine and codeine), anesthetics (γ-hydroxybutyric acid, propofol, ketamine and phencyclidine) and cognitive enhancers (methylphenidate and modafinil), and some important plant-derived hallucinogens (lysergide, salvinorin A, psilocybin and psilocin), as well as of nicotine in humans are summarized in this article. The isoenzymes (e.g., cytochrome P450, glucuronyltransferases, esterases and reductases) involved in the metabolism of drugs and some pharmacokinetic data are discussed. The relevance of such data is discussed for predicting possible interactions with other xenobiotics, understanding pharmacokinetic behavior and pharmacogenomic variations, assessing toxic risks, developing suitable toxicological analysis procedures, and finally for interpretating drug testing results.

Effect of piperine, a major component of black pepper, on the intestinal absorption of fexofenadine and its implication on food-drug interaction

The present study aimed to investigate the effect of piperine, a major component of black pepper, on the oral exposure of fexofenadine in rats. Pharmacokinetic parameters of fexofenadine were determined in rats following an oral (10 mg/kg) or intravenous (5 mg/kg) administration of fexofenadine in the presence and absence of piperine (10 or 20 mg/kg, given orally). Compared to the control group given fexofenadine alone, the combined use of piperine increased the oral exposure (AUC) of fexofenadine by 180% to 190% while there was no significant change in C(max) and T(1/2) of fexofenadine in rats. The bioavailability of fexofenadine was increased by approximately 2-folds via the concomitant use of piperine. Furthermore, T(max) tends to be increased which might be attributed to the delayed gastric emptying in the presence of piperine. In contrast, piperine did not alter the intravenous pharmacokinetics of fexofenadine, implying that piperine may increase mainly the gastrointestinal absorption of fexofenadine rather than reducing hepatic extraction. In conclusion, piperine significantly enhanced the oral exposure of fexofenadine in rats likely by the inhibition of P-glycoprotein-mediated cellular efflux during the intestinal absorption, suggesting that the combined use of piperine or piperine-containing diet with fexofenadine may require close monitoring for potential drug-diet interactions.

Modulation of the activity of ABC transporters (P-glycoprotein, MRP2, BCRP) by flavonoids and drug response

The present article aims to review the up-to-date information on the most recent studies of the interaction of flavonoids with ABC transporters, in particular the drug pharmacokinetic consequences of such a relationship. In addition, the modulation of the expression of the ABC transporters by flavonoids is also illustrated. Flavonoids are a large group of plant polyphenols present extensively in our daily diets and herbal products. High intake of isoflavones has been associated with a variety of beneficial effects on several common diseases. These polyphenols interact with ABC drug transporters involved in drug resistance and drug absorption, distribution and excretion. A number of studies have demonstrated inhibition of drug transporters by flavonoids. This flavonoid-ABC-transporter interaction could be beneficial for poorly absorbed drugs but could also result in severe drug intoxication, especially drugs with a narrow therapeutic window. On the other hand, flavonoids are themselves substrates of ABC transporters. These proteins can affect the oral availability and tissue distribution of these compounds, modifying their beneficial effects. The challenge is to find a suitable way to predict harmful drug-flavonoid interactions mediated by these transporters.

P-glycoprotein, multidrug resistance-associated proteins and human organic anion transporting polypeptide influence the intracellular accumulation of atazanavir

BACKGROUND

Drug efflux (for example, P-glycoprotein [P-gp], multidrug resistance-associated proteins [MRPs] and breast cancer resistance protein [BCRP]) and influx (for example, human organic anion transporting polypeptide [hOCTP] or human organic anion transporting polypeptide [hOATP]) transporters alter the cellular concentrations of some HIV protease inhibitors (HPIs). Here, we studied the lipophilicity and uptake of [(3)H]-atazanavir (ATV) in CEM (parental), CEM(VBL) (P-gp-overexpressing), CEM(E1000) (MRP1-overexpressing) and peripheral blood mononuclear cells (PBMCs), and evaluate the effects of modulators of drug transporters on uptake.

METHODS

Lipophilicity was measured by octanol/saline partition method. The influence of influx/efflux transporters on uptake was evaluated in the absence and presence of inhibitors of P-gp (GPV031), P-gp/BCRP (tariquidar and GF120918), P-gp/MRP1 (dipyridamole and daidzein), MRP1/2 (frusemide and genistein), hOATP/hOCTP (estrone-3-sulfate [E-3-S]) and hOATP/hOCTP/MRP (probenecid). The effects of a number of HPIs on uptake were also evaluated. Data from digitonin permeabilized cells allowed the evaluation of the contribution of cellular binding to total drug uptake, whereas the inhibitory effect of ATV on P-gp was assessed by daunomycin efflux/uptake assays.

RESULTS

[(3)H]-ATV is lipophilic and accumulates in the cultured cells as follows: CEM>CEM(E1000)>CEM(VBL). Tariquidar, GF120918 and daidzein significantly increased the uptake of [(3)H]-ATV in the cultured cells. By contrast, only daidzein and tipranavir significantly increased uptake in PBMCs, with tariquidar and frusemide devoid of effects, whereas dipyridamole, E-3-S, GPV031 and genistein significantly decreased accumulation. ATV inhibits P-gp activity; manipulation of uptake with digitonin suggests binding of [(3)H]-ATV to P-gp.

CONCLUSIONS

[(3)H]-ATV is lipophilic, a P-gp, MRP and hOATP substrate and an inhibitor of P-gp. Concomitant administration of ATV with drugs and dietary components (for example, daidzein and genistein) that interact with these transporters could alter its pharmacokinetics.

Effect of hesperidin on the oral pharmacokinetics of diltiazem and its main metabolite, desacetyldiltiazem, in rats

Objectives

This study was to investigate the effect of hesperidin, an antioxidant, on the bioavailability and pharmacokinetics of diltiazem and its active major metabolite, desacetyldiltiazem, in rats.

Methods

A single dose of diltiazem was administered orally (15 mg/kg) in the presence or absence of hesperidin (1, 5 or 15 mg/kg), which was administered 30 min before diltiazem.

Key findings

Compared with the control group (given diltiazem alone), hesperidin (5 or 15 mg/kg) significantly altered the pharmacokinetic parameters of diltiazem, except for 1 mg/kg hesperidin. The area under the plasma concentration-time curve from time 0 h to infinity (AUC0-∞) was significantly (5 mg/kg, P &lt; 0.05; 15 mg/kg, P &lt; 0.01) increased by 48.9–65.3% and the peak plasma concentration (Cmax) was significantly (P &lt; 0.05) increased by 46.7–62.4% in the presence of hesperidin (5 or 15 mg/kg). Consequently, the absolute bioavailability (F) of diltiazem with hesperidin was significantly (5 mg/kg, P &lt; 0.05; 15 mg/kg, P &lt; 0.01) higher than that in the control group. Hesperidin (5 or 15 mg/kg) significantly (P &lt; 0.05) increased the AUC0-∞ and 15 mg/kg of hesperidin significantly (P &lt; 0.05) increased the Cmax of desacetyldiltiazem. However, the metabolite-parent ratio (MR) of desacetyldiltiazem was not significantly changed in the presence of hesperidin.

Conclusions

Hesperidin significantly enhanced the oral bioavailability of diltiazem in rats. It might be considered that hesperidin increased the intestinal absorption and reduced the first-pass metabolism of diltiazem in the intestine and in the liver via an inhibition of cytochrome P450 3A or P-glycoprotein.

Dietary salt does not influence the disposition of verapamil enantiomers in relation to efflux transporter ABCB1 genetic polymorphism in healthy Korean subjects

To evaluate the effects of dietary salt on the stereoselective disposition of verapamil enantiomers in relation to the transporter ABCB1 2677GG/3435CC and 2677TT/3435TT haplotypes, ten healthy subjects were asked to take diets of three different salt levels for 7 days in a randomized, three-way crossover manner. The plasma concentrations of verapamil and norverapamil enantiomers were determined after a single oral dose of 240 mg verapamil on the last day of each phase. Pharmacokinetic parameters were calculated by non-compartmental analysis techniques and compared among the three different dietary salt phases. Compared with the medium salt diet, the high and low salt diets had no significant effect on the disposition of verapamil enantiomers. Moreover, the ABCB1 haplotypes did not alter the impact of dietary salt, although ABCB1 2677TT/3435TT subjects had slightly, but not significantly, higher C(max) and area under the curve (AUC) and lower T(max) for the verapamil enantiomers than did 2677GG/3435CC subjects in each salt phase.

Influence of food on the oral bioavailability of rupatadine tablets in healthy volunteers: a single-dose, randomized, open-label, two-way crossover study

BACKGROUND

Rupatadine is an oral active antihistamine for the management of diseases with allergic inflammatory conditions, such as perennial and seasonal rhinitis and chronic idiopathic urticaria. Oral rupatadine has been approved for the treatment of allergic rhinitis and chronic urticaria in adults and adolescents in several European countries.

OBJECTIVE

The purpose of this study was to describe the effect of the concomitant intake of food on the pharmacokinetic profile and bioavailability of a single dose of rupatadine.

METHODS

This was a single-dose, randomized, open-label, 2-way crossover study in which healthy male and female volunteers received a single, 20-mg oral dose of rupatadine under fed and fasting conditions. Blood samples were collected and plasma concentrations of rupatadine and its active metabolites desloratadine and 3-hydroxydesloratadine were determined by liquid chromatography tandem mass spectrometry. Tolerability was based on the recording of adverse events (AEs), physical examinations, electrocardiograms, and laboratory tolerability tests immediately before each treatment period and at the final visit of the study.

RESULTS

Twenty-four volunteers (12 males; mean [SD] age, 25.4 [5.3] years [range, 18-34 years]; mean [SD] weight, 71.2 [4.3] kg [range, 64-77 kg]; 12 females; mean [SD] age, 26.8 [6.5] years [range, 18-38 years]; mean [SD] weight, 58.4 [6.8] kg, [range 50-69 kg]) were enrolled and randomized with equal distribution of sex. A significant increase in AUC from drug administration to the final quantifiable sample (AUC(0-t)) and AUC from drug administration to infinity (AUC(0-infinity)) values of rupatadine was seen under fed conditions without affecting C(max). The ratios (90% CI) of the mean log-transformed AUC(0-t) and AUC(0-infinity) for rupatadine revealed a significant increase in AUC(0-t) (ratio 131%; 90% CI, 111%-154%) and AUC(0-infinity) (ratio 133%; 90% CI, 113%-156%), whereas C(max) remained unaltered (ratio 97%; 90% CI, 80%-116%). Plasma concentration-time profiles of desloratadine and 3-hydroxydesloratadine were similar with and without food, and no differences were seen for AUC(0-t), AUC(0-infinity), or C(max). Seven (28%) subjects reported > or =1 AE. All AEs were mild, resolved spontaneously, and did not affect the outcome of the study.

CONCLUSIONS

The results of this study indicate that concomitant intake of food with a single 20-mg oral dose of rupatadine exhibits a significant increase in rupatadine bioavailability. Despite the absence of bioequivalence, the drug was well tolerated under fed and fasting conditions, and no major changes in severity and/or prevalence of AEs were reported.

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.

Possible inhibitory mechanism of Curcuma drugs on CYP3A4 in 1α,25 dihydroxyvitamin D3 treated Caco-2 cells

Curcuma longa and C. zedoaria, belonging to genus Curcuma, have become prevalent as supplements in East Asia. Curcumin is the most well-studied bioactive component isolated from rhizomes of C. longa and other Curcuma species except C. zedoaria. In this study, we investigated the affects of C. longa, C. zedoaria from Japan and curcumin on CYP3A4. Caco-2 cells, in which CYP3A4 expression was induced by 1alpha,25-(OH)(2)-D(3), were used to mimic the metabolism of small intestine. Caco-2 cells were treated with methanol extracts from two Curcuma rhizomes (0.1mg/ml) or curcumin (30 microM) for 72 h. Both extracts significantly decreased the activity of CYP3A4 by about 85-98%. The 50% inhibitory concentrations of C. longa and C. zedoaria extracts were 0.019 and 0.014 mg/ml, respectively. They caused a 60-70% decrease in CYP3A4 protein. Otherwise, curcumin treatment caused a 30-40% decrease in CYP3A4 catalytic activity and a 38% decrease in CYP3A4 protein expression. Moreover, it was found that both Curcuma extracts and curcumin treatment had no influence on CYP3A4 mRNA expression. Our results suggested that administration of Curcuma drugs might inhibit the catalytic activity of intestinal CYP3A4. However, curcumin was not the major compound responsible for this inhibitory effect.

Drug-drug and food-drug pharmacokinetic interactions with new insulinotropic agents repaglinide and nateglinide

This review describes the current knowledge on drug-drug and food-drug interactions with repaglinide and nateglinide. These two meglitinide derivatives, commonly called glinides, have been developed for improving insulin secretion of patients with type 2 diabetes mellitus. They are increasingly used either in monotherapy or in combination with other oral antihyperglycaemic agents for the treatment of type 2 diabetes. Compared with sulfonylureas, glinides have been shown to (i) provide a better control of postprandial hyperglycaemia, (ii) overcome some adverse effects, such as hypoglycaemia, and (iii) have a more favourable safety profile, especially in patients with renal failure. The meal-related timing of administration of glinides and the potential influence of food and meal composition on their bioavailability may be important. In addition, some food components (e.g. grapefruit juice) may cause pharmacokinetic interactions. Because glinides are metabolised via cytochrome P450 (CYP) 3A4 isoenzyme, they are indeed exposed to pharmacokinetic interactions. In addition to CYP3A4, repaglinide is metabolised via CYP2C8, while nateglinide metabolism also involves CYP2C9. Furthermore, both compounds and their metabolites may undergo specialised transport/uptake in the intestine, another source of pharmacokinetic interactions. Clinically relevant drug-drug interactions are those that occur when glinides are administered together with other glucose-lowering agents or compounds widely coadministered to diabetic patients (e.g. lipid-lowering agents), with drugs that are known to induce (risk of lower glinide plasma levels and thus of deterioration of glucose control) or inhibit (risk of higher glinide plasma levels leading to hypoglycaemia) CYP isoenzymes concerned in their metabolism, or with drugs that have a narrow efficacy : toxicity ratio. Pharmacokinetic interactions reported in the literature appear to be more frequent and more important with repaglinide than with nateglinide. Rifampicin (rifampin) reduced repaglinide area under the plasma concentration-time curve (AUC) by 32-85% while it reduced nateglinide AUC by almost 25%. Reported increases in AUCs with coadministration of drugs inhibiting CYP isoenzymes never exceeded 80% for repaglinide (except with ciclosporin and with gemfibrozil) and 50% for nateglinide. Ciclosporin more than doubled repaglinide AUC (+144%), a finding that should raise caution when using these two drugs in combination. The most impressive pharmacokinetic interaction was reported with combined administration of gemfibrozil (a strong CYP2C8 inhibitor) and repaglinide (8-fold increase in repaglinide AUC). Although no studies have been performed in patients with type 2 diabetes, the latter combination should be avoided in clinical practice.

Clinical relevance of the small intestine as an organ of drug elimination: drug-fruit juice interactions

Most drugs are taken orally. For those intended to act systemically, a significant fraction of the dose can be eliminated during its first passage through a sequence of organs before entry into the general circulation. For some drugs, the degree of first-pass elimination can be large enough such that oral bioavailability is significantly reduced, with the consequent potential for a reduced clinical response. Of these first-pass eliminating organs, the small intestine and liver are the most commonly implicated, in part because they express the highest levels of drug-metabolizing enzymes. For several drugs whose major route of elimination occurs via CYP3A-mediated metabolism, the extent of first-pass metabolism in the small intestine can rival that in the liver. As such, alterations in enteric CYP3A activity alone can significantly influence oral bioavailability. The most extensively studied xenobiotic shown to inhibit only enteric CYP3A is grapefruit juice, the consequences of which can be clinically significant. Although much information has been gained regarding the grapefruit juice effect, progress in the relatively understudied area of drug-diet interactions continues to be sluggish and reactive. In stark contrast, the potential for drug-drug interactions involving any new therapeutic agent must be evaluated, prospectively, before market introduction. To prospectively elucidate mechanisms underlying drug-diet interactions, a multidisciplinary, translational research approach is required, which capitalizes on the collective expertise of drug metabolism scientists and natural products chemists. Such an approach would allow proper between-study comparisons, and ultimately provide conclusive information as to whether specific dietary substances can be taken safely with certain medications.

Toxicokinetics of drugs of abuse: current knowledge of the isoenzymes involved in the human metabolism of tetrahydrocannabinol, cocaine, heroin, morphine, and codeine

This review summarizes the major metabolic pathways of the drugs of abuse, tetrahydrocannabinol, cocaine, heroin, morphine, and codeine, in humans including the involvement of isoenzymes. This knowledge may be important for predicting their possible interactions with other xenobiotics, understanding pharmaco-/toxicokinetic and pharmacogenetic variations, toxicological risk assessment, developing suitable toxicological analysis procedures, and finally for understanding certain pitfalls in drug testing. The detection times of these drugs and/or their metabolites in biological samples are summarized and the implications of the presented data on the possible interactions of drugs of abuse with other xenobiotics, ie, inhibition or induction of individual polymorphic and nonpolymorphic isoenzymes, discussed.

Clinical implications ofCYP3Apolymorphisms

Due to their enormous substrate spectrum CYP3A4, -3A5 and -3A7 constitute the most important drug-metabolising enzyme subfamily in humans. CYP3As are expressed predominantly, but not exclusively, in the liver and intestine, where they participate in the metabolism of 45 - 60% of currently used drugs and many other compounds such as steroids and carcinogens. CYP3A expression and activity vary interindividually due to a combination of genetic and nongenetic factors such as hormone and health status, and the impact of environmental stimuli. Over the past several years, genetic determinants have been identified for much of the variable expression of CYP3A5 and -3A7, but not for CYP3A4. Using these markers, an effect of CYP3A5 expression status has been demonstrated beyond doubt for therapies with the immunosuppressive drug tacrolimus. Further associations are likely to emerge for drugs metabolised predominantly by CYP3A5 or -3A7, especially for individuals or tissues with concomitant low expression of CYP3A4. However, as exemplified by the controversial association between CYP3A4*1B and prostate cancer, the detection of clinical effects of CYP3A gene variants will be difficult. The most important underlying problems are the continuing absence of activity markers specific for CYP3A4 and the strong contribution of nongenetic factors to CYP3A variability.

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.

Inhibition of P-glycoprotein-mediated transport by extracts of and monoterpenoids contained in Zanthoxyli fructus

Citrus (rutaceous) herbs are often used in traditional medicine and Japanese cuisine and can be taken concomitantly with conventional medicine. In this study, the effect of various citrus-herb extracts on P-glycoprotein (P-gp)-mediated transport was examined in vitro to investigate a possible interaction with P-gp substrates. Component monoterpenoids of the essential oil in Zanthoxyli fructus was screened to find novel P-gp inhibitors. LLC-GA5-COL150 cells transfected with human MDR1 cDNA encoding P-gp were used. Cellular accumulation of [3H]digoxin was measured in the presence or absence of P-gp inhibitors or test samples. Aurantii fructus, Evodiae fructus, Aurantii fructus immaturus, Aurantii nobilis pericarpium, Phellodendri cortex, and Zanthoxyli fructus were extracted with hot water (decocted) and then fractionated with ethyl acetate. The cell to medium ratio of [3H]digoxin accumulation increased significantly in the presence of the decoction of Evodiae fructus, Aurantii nobilis pericarpium, and Zanthoxyli fructus, and the ethyl acetate fraction of all citrus herbs used. The ethyl acetate fraction of Zanthoxyli fructus exhibited the strongest inhibition of P-gp among tested samples with an IC50 value of 166 microg/mL. Then its component monoterpenoids, geraniol, geranyl acetate, (R)-(+)-limonene, (R)-(+)-linalool, citronellal, (R)-(+)-citronellal, DL-citronellol, (S)-(-)-beta-citronellol, and cineole, were screened. (R)-(+)-citronellal and (S)-(-)-beta-citronellol inhibited P-gp with IC50 values of 167 microM and 504 microM, respectively. These findings suggest that Zanthoxyli fructus may interact with P-gp substrates and that some monoterpenoids with the relatively lower molecular weight of about 150 such as (R)-(+)-citronellal can be potent inhibitors of P-gp.

Dietary flavonoids: effects on xenobiotic and carcinogen metabolism

Flavonoids are present in fruits, vegetables and beverages derived from plants (tea, red wine), and in many dietary supplements or herbal remedies including Ginkgo Biloba, Soy Isoflavones, and Milk Thistle. Flavonoids have been described as health-promoting, disease-preventing dietary supplements, and have activity as cancer preventive agents. Additionally, they are extremely safe and associated with low toxicity, making them excellent candidates for chemopreventive agents. The cancer protective effects of flavonoids have been attributed to a wide variety of mechanisms, including modulating enzyme activities resulting in the decreased carcinogenicity of xenobiotics. This review focuses on the flavonoid effects on cytochrome P450 (CYP) enzymes involved in the activation of procarcinogens and phase II enzymes, largely responsible for the detoxification of carcinogens. A number of naturally occurring flavonoids have been shown to modulate the CYP450 system, including the induction of specific CYP isozymes, and the activation or inhibition of these enzymes. Some flavonoids alter CYPs through binding to the aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor, acting as either AhR agonists or antagonists. Inhibition of CYP enzymes, including CYP 1A1, 1A2, 2E1 and 3A4 by competitive or mechanism-based mechanisms also occurs. Flavones (chrysin, baicalein, and galangin), flavanones (naringenin) and isoflavones (genistein, biochanin A) inhibit the activity of aromatase (CYP19), thus decreasing estrogen biosynthesis and producing antiestrogenic effects, important in breast and prostate cancers. Activation of phase II detoxifying enzymes, such as UDP-glucuronyl transferase, glutathione S-transferase, and quinone reductase by flavonoids results in the detoxification of carcinogens and represents one mechanism of their anticarcinogenic effects. A number of flavonoids including fisetin, galangin, quercetin, kaempferol, and genistein represent potent non-competitive inhibitors of sulfotransferase 1A1 (or P-PST); this may represent an important mechanism for the chemoprevention of sulfation-induced carcinogenesis. Importantly, the effects of flavonoids on enzymes are generally dependent on the concentrations of flavonoids present, and the different flavonoids ingested. Due to the low oral bioavailability of many flavonoids, the concentrations achieved in vivo following dietary administration tend to be low, and may not reflect the concentrations tested under in vitro conditions; however, this may not be true following the ingestion of herbal preparations when much higher plasma concentrations may be obtained. Effects will also vary with the tissue distribution of enzymes, and with the species used in testing since differences between species in enzyme activities also can be substantial. Additionally, in humans, marked interindividual variability in drug-metabolizing enzymes occurs as a result of genetic and environmental factors. This variability in xenobiotic metabolizing enzymes and the effect of flavonoid ingestion on enzyme expression and activity can contribute to the varying susceptibility different individuals have to diseases such as cancer. As well, flavonoids may also interact with chemotherapeutic drugs used in cancer treatment through the induction or inhibition of their metabolism.

Enhanced oral exposure of diltiazem by the concomitant use of naringin in rats

The present study aims to investigate the effect of naringin, a flavonoid, on the pharmacokinetics of diltiazem and its active metabolite, desacetyldiltiazem, in rats. Pharmacokinetic parameters of diltiazem and desacetyldiltiazem were determined in rats following an oral administration of diltiazem (15 mgkg(-1)) to rats in the presence and absence of naringin (5 and 15 mgkg(-1)). Compared to the control given diltiazem alone, the C(max) and AUC of diltiazem increased by twofolds in rats pretreated with naringin, while there was no significant change in T(max) and terminal plasma half-life (T(1/2)) of diltiazem. Consequently, absolute and relative bioavailability values of diltiazem in the presence of naringin were significantly higher (p<0.05) than those from the control group. Metabolite-parent AUC ratio in the presence of naringin decreased by 30% compared to the control group, implying that naringin could be effective to inhibit the metabolism of diltiazem. In conclusion, the concomitant use of naringin significantly enhanced the oral exposure of diltiazem in rats.

Intestinal uptake of MPP+ is differently affected by red and white wine

It is becoming increasingly evident that ingested products, such as wine, may have profound effects on the therapeutic efficacy of certain drugs. As various xeno- and endobiotics are organic cations, the purpose of our study was to examine the modulation of organic cations intestinal apical uptake by red (RW) and white wine (WW). For this purpose, we used RW, WW, the same alcohol-free wines, phenolic compounds and ethanol. The uptake of the organic cation 1-methyl-4-phenylpyridinium (MPP+) was evaluated in Caco-2 cells, an intestinal epithelial cell model. RW and alcohol-free RW increased 3H-MPP+ apical uptake, although the effect of alcohol-free RW was less pronounced. On the other hand, WW and alcohol-free WW decreased the organic cation uptake but the effect of alcohol-free WW was more pronounced. Our results show that the total content in phenolic compounds was 7 times higher, and the dialysis index was about 4 times higher in RW compared to WW. Ethanol, in the same concentration found in wine, caused a significant decrease in 3H-MPP+ apical uptake. The solution containing high molecular weight compounds from dialyzed RW increased 3H-MPP+ apical uptake. In conclusion, the results suggest that RW may increase and WW may reduce the intestinal absorption of organic cations present in the diet, such as drugs or vitamins (e.g. thiamine and riboflavin). As ethanol alone decreased the uptake of MPP+, and alcohol-free RW and WW had a lower potency than intact wine upon the transport, the presence of ethanol is probably important for the solubilisation/bioavailability of the components endowed with the transport modulating activity.