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Hepatic Metabolism (hepatic + metabolism)
Selected AbstractsQuantitative tests of liver function measure hepatic improvement after sustained virological response: results from the HALT-C trialALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 5 2009G. T. EVERSON Summary Backgroud, The impact of virologic response on hepatic function has not been previously defined. Aim, To determine the relationships of quantitative liver function tests (QLFTs) with virological responses to peginterferon (PEG) ± ribavirin (RBV) in patients with chronic hepatitis C and to use serial QLFTs to define the spectrum of hepatic improvement after sustained virological response (SVR). Methods, Participants (n = 232) were enrolled in the Hepatitis C Antiviral Long-term Treatment against Cirrhosis (HALT-C) Trial, had failed prior therapy, had bridging fibrosis or cirrhosis and were retreated with PEG/RBV. All 232 patients had baseline QLFTs; 24 patients with SVR and 68 nonresponders had serial QLFTs. Lidocaine, [24- 13C]cholate, galactose and 99mTc-sulfur colloid were administered intravenously; [2,2,4,2- 2H]cholate, [1- 13C]methionine, caffeine and antipyrine were administered orally. Clearances (Cl), breath 13CO2, monoethylglycylxylidide (MEGX), perfused hepatic mass (PHM) and liver volume were measured. Results, Rates of SVR were 18,26% in patients with good function by QLFTs, but ,6% in patients with poor function. Hepatic metabolism, measured by caffeine kelim (P = 0.02), antipyrine kelim (P = 0.05) and antipyrine Cl (P = 0.02) and the portal circulation, measured by cholate Cloral (P = 0.0002) and cholate shunt (P = 0.0003) and PHM (P = 0.03) improved after SVR. Conclusion, Hepatic dysfunction impairs the virological response to PEG/RBV. SVR improves hepatic metabolism, the portal circulation and PHM. [source] AMP-activated protein kinase in the regulation of hepatic energy metabolism: from physiology to therapeutic perspectivesACTA PHYSIOLOGICA, Issue 1 2009B. Viollet Abstract As the liver is central in the maintenance of glucose homeostasis and energy storage, knowledge of the physiology as well as physiopathology of hepatic energy metabolism is a prerequisite to our understanding of whole-body metabolism. Hepatic fuel metabolism changes considerably depending on physiological circumstances (fed vs. fasted state). In consequence, hepatic carbohydrate, lipid and protein synthesis/utilization are tightly regulated according to needs. Fatty liver and hepatic insulin resistance (both frequently associated with the metabolic syndrome) or increased hepatic glucose production (as observed in type 2 diabetes) resulted from alterations in substrates oxidation/storage balance in the liver. Because AMP-activated protein kinase (AMPK) is considered as a cellular energy sensor, it is important to gain understanding of the mechanism by which hepatic AMPK coordinates hepatic energy metabolism. AMPK has been implicated as a key regulator of physiological energy dynamics by limiting anabolic pathways (to prevent further ATP consumption) and by facilitating catabolic pathways (to increase ATP generation). Activation of hepatic AMPK leads to increased fatty acid oxidation and simultaneously inhibition of hepatic lipogenesis, cholesterol synthesis and glucose production. In addition to a short-term effect on specific enzymes, AMPK also modulates the transcription of genes involved in lipogenesis and mitochondrial biogenesis. The identification of AMPK targets in hepatic metabolism should be useful in developing treatments to reverse metabolic abnormalities of type 2 diabetes and the metabolic syndrome. [source] The pharmacology of cilostazolDIABETES OBESITY & METABOLISM, Issue 2002Karsten Schrör Cilostazol (6-[4-(1-cyclohexyl- 1H -tetrazol-5-yl)butoxy]-3,4-dihydro-2(1H)-quinolinone; OPC-13013) is a 2-oxo-quinoline derivative with antithrombotic, vasodilator, antimitogenic and cardiotonic properties. The compound is a potent inhibitor of phosphodiesterase (PDE) 3A, the isoform of PDE 3 in the cardiovascular system (IC50: 0.2 µm). In addition, there is inhibition of adenosine uptake, eventually resulting in changes in cAMP levels, dependent on the type of adenosine receptors (A1 or A2). Cilostazol inhibits platelet aggregation and has considerable antithrombotic effects in vivo. The compound relaxes vascular smooth muscle and inhibits mitogenesis and migration of vascular smooth muscle cells. In the heart, cilostazol causes positive inotropic and chronotropic effects. Most, if not all, of these actions are cAMP-mediated, including the modification of cAMP-controlled gene expression. Cilostazol decreases levels of serum triglycerides and causes some increase in HDL-cholesterol levels. The compound has a number of additional effects which might contribute to its overall clinical efficacy. Cilostazol undergoes intensive and finally complete hepatic metabolism via the cytochrome P450 systems. This might result in some drug interaction, i.e. with erythromycin and omeprazole. The half-life is approximately 10 h, resulting in about 2-fold accumulation of the drug during repeated administration. [source] Effects of a new 1,3,4-thiadiazolium mesoionic compound, MI-D, on the acute inflammatory responseDRUG DEVELOPMENT RESEARCH, Issue 4 2004Jślio C. Cardoso Abstract A new mesoionic compound, 4-phenyl-5-(4-nitro-cinnamoyl)-1,3,4-thiadiazolium-2-phenylamine (MI-D), is described along with some of its biological properties. Its effects on hepatic metabolism, on O and nitric oxide (NO) production, and in in vivo models for potential antinociceptive, antipyretic, and antiinflammatory activities were determined. In perfused rat liver, MI-D (25 µM) stimulated glycogenolysis (95%), and inhibited oxygen uptake (37%) with affecting glycolysis. In phorbol 12-myristate 13-acetate-stimulated macrophages, O generation was reduced (95%) by MI-D (15 µM), whereas the production of NO was unaffected. MI-D (2 mg/kg) inhibited (55%) the number of abdominal writhings induced by acetic acid. At 1 mg/kg, MI-D inhibited the febrile response (5 h) induced by lipopolysaccharide (LPS) and was also effective against a preexisting febrile response. Treatment with MI-D (1 mg/kg) reduced by 67% prostaglandin (PGE2) levels in the cerebrospinal fluid of LPS-exposed mice, and at a higher dose (8 mg/kg) MI-D inhibited paw edema formation (2 h) induced by carrageenan. MI-D has a spectrum of activities similar to other nonsteroidal antiinflammatory drugs, qualifying it as a potential anti-inflammatory drug. Drug Dev. Res. 61:207,217, 2004. © 2004 Wiley-Liss, Inc. [source] Toll-like receptor 4 status influences hepatic metabolism, although its interaction with a high-fructose, energy, and prebiotic diet remains uncertain,HEPATOLOGY, Issue 4 2010Richard D. Johnston No abstract is available for this article. [source] Increasing dimethylarginine levels are associated with adverse clinical outcome in severe alcoholic hepatitis,HEPATOLOGY, Issue 1 2007Rajeshwar P. Mookerjee Previous studies suggest reduced hepatic endothelial nitric oxide synthase activity contributes to increased intrahepatic resistance. Asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor, undergoes hepatic metabolism via dimethylarginine-dimethylamino-hydrolase, and is derived by the action of protein-arginine-methyltransferases. Our study assessed whether ADMA, and its stereo-isomer symmetric dimethylarginine (SDMA), are increased in alcoholic hepatitis patients, and determined any relationship with severity of portal hypertension (hepatic venous pressure gradient measurement) and outcome. Fifty-two patients with decompensated alcoholic cirrhosis were studied, 27 with acute alcoholic hepatitis and cirrhosis, in whom hepatic venous pressure gradient was higher (P = 0.001) than cirrhosis alone, and correlated with ADMA measurement. Plasma ADMA and SDMA were significantly higher in alcoholic hepatitis patients and in nonsurvivors. Dimethylarginine-dimethylamino-hydrolase protein expression was reduced and protein-arginine-methyltransferase-1 increased in alcoholic hepatitis livers. ADMA, SDMA and their combined sum, which we termed a dimethylarginine score, were better predictors of outcome compared with Pugh score, MELD and Maddrey's discriminant-function. Conclusion: Alcoholic hepatitis patients have higher portal pressures associated with increased ADMA, which may result from both decreased breakdown (decreased hepatic dimethylarginine-dimethylamino-hydrolase) and/or increased production. Elevated dimethylarginines may serve as important biological markers of deleterious outcome in alcoholic hepatitis. (HEPATOLOGY 2007;45:62,71.) [source] Intrahepatic amino acid and glucose metabolism in a D -galactosamine,induced rat liver failure modelHEPATOLOGY, Issue 2 2001Kosuke Arai A better understanding of the hepatic metabolic pathways affected by fulminant hepatic failure (FHF) would help develop nutritional support and other nonsurgical medical therapies for FHF. We used an isolated perfused liver system in combination with a mass-balance model of hepatic intermediary metabolism to generate a comprehensive map of metabolic alterations in the liver in FHF. To induce FHF, rats were fasted for 36 hours, during which they received 2 D -galactosamine injections. The livers were then perfused for 60 minutes via the portal vein with amino acid,supplemented Eagle minimal essential medium containing 3% wt/vol bovine serum albumin and oxygenated with 95% O2/5% CO2. Control rats were fasted for 36 hours with no other treatment before perfusion. FHF rat livers exhibited reduced amino acid uptake, a switch from gluconeogenesis to glycolysis, and a decrease in urea synthesis, but no change in ammonia consumption compared with normal fasted rat livers. Mass-balance analysis showed that hepatic glucose synthesis was inhibited as a result of a reduction in amino acid entry into the tricarboxylic acid cycle by anaplerosis. Furthermore, FHF inhibited intrahepatic aspartate synthesis, which resulted in a 50% reduction in urea cycle flux. Urea synthesis by conversion of exogenous arginine to ornithine was unchanged. Ammonia removal was quantitatively maintained by glutamine synthesis from glutamate and a decrease in the conversion of glutamate to ,-ketoglutarate. Mass-balance analysis of hepatic metabolism will be useful in characterizing changes during FHF, and in elucidating the effects of nutritional supplements and other treatments on hepatic function. [source] Circulating adiponectin reflects severity of liver disease but not insulin sensitivity in liver cirrhosisJOURNAL OF INTERNAL MEDICINE, Issue 3 2005S. KASER Abstract. Background., The adipocytokine adiponectin has been proposed to play important roles in the regulation of energy homeostasis, insulin sensitivity and shows anti-inflammatory properties. Aim., In this study we investigated the role of circulating adiponectin in different chronic liver diseases, its regulation by systemic anti-tumour necrosis factor (TNF)- , treatment and its hepatic metabolism. Patients and methods., Plasma adiponectin levels were determined in 87 patients with liver cirrhosis of different aetiologies, seven patients with alcoholic steatohepatitis undergoing systemic anti-TNF- , treatment, in 11 patients with liver cirrhosis receiving transjugular intrahepatic portosystemic shunt implantation and in 21 healthy controls. Results., Adiponectin levels were significantly higher in all subjects with liver cirrhosis of different aetiologies when compared with healthy controls and increased dependent on Child-Pugh classification. In subjects with alcoholic steatohepatitis, systemic anti-TNF- , treatment caused a significant decrease in circulating adiponectin. Adiponectin concentrations were similar in portal, hepatic and peripheral veins. No correlation between adiponectin levels and insulin resistance was found in any patient group. Conclusions., Our data suggest that circulating adiponectin is increased in liver cirrhosis independent of the aetiology of liver disease. We suggest that high adiponectin levels in chronic liver disease might reflect one of the body's anti-inflammatory mechanisms in chronic liver diseases. [source] Physiologically based predictions of the impact of inhibition of intestinal and hepatic metabolism on human pharmacokinetics of CYP3A substratesJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 1 2010Frederique Fenneteau Abstract The first objective of the present study was to predict the pharmacokinetics of selected CYP3A substrates administered at a single oral dose to human. The second objective was to predict pharmacokinetics of the selected drugs in presence of inhibitors of the intestinal and/or hepatic CYP3A activity. We developed a whole-body physiologically based pharmacokinetics (WB-PBPK) model accounting for presystemic elimination of midazolam (MDZ), alprazolam (APZ), triazolam (TRZ), and simvastatin (SMV). The model also accounted for concomitant administration of the above-mentioned drugs with CYP3A inhibitors, namely ketoconazole (KTZ), itraconazole (ITZ), diltiazem (DTZ), saquinavir (SQV), and a furanocoumarin contained in grape-fruit juice (GFJ), namely 6,,7,-dihydroxybergamottin (DHB). Model predictions were compared to published clinical data. An uncertainty analysis was performed to account for the variability and uncertainty of model parameters when predicting the model outcomes. We also briefly report on the results of our efforts to develop a global sensitivity analysis and its application to the current WB-PBPK model. Considering the current criterion for a successful prediction, judged satisfied once the clinical data are captured within the 5th and 95th percentiles of the predicted concentration,time profiles, a successful prediction has been obtained for a single oral administration of MDZ and SMV. For APZ and TRZ, however, a slight deviation toward the 95th percentile was observed especially for Cmax but, overall, the in vivo profiles were well captured by the PBPK model. Moreover, the impact of DHB-mediated inhibition on the extent of intestinal pre-systemic elimination of MDZ and SMV has been accurately predicted by the proposed PBPK model. For concomitant administrations of MDZ and ITZ, APZ and KTZ, as well as SMV and DTZ, the in vivo concentration,time profiles were accurately captured by the model. A slight deviation was observed for SMV when coadministered with ITZ, whereas more important deviations have been obtained between the model predictions and in vivo concentration,time profiles of MDZ coadministered with SQV. The same observation was made for TRZ when administered with KTZ. Most of the pharmacokinetic parameters predicted by the PBPK model were successfully predicted within a two-fold error range either in the absence or presence of metabolism-based inhibition. Overall, the present study demonstrated the ability of the PBPK model to predict DDI of CYP3A substrates with promising accuracy. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:486,514, 2010 [source] Metabolism and disposition of resveratrol in the isolated perfused rat liver: Role of Mrp2 in the biliary excretion of glucuronidesJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 4 2008Alexandra Maier-Salamon Abstract In this study, the hepatic metabolism and transport system for resveratrol was examined in isolated perfused livers from Wistar and Mrp2-deficient TR, rats. Based on extensive metabolism to six glucuronides and sulfates (M1,M6), the hepatic extraction ratio and clearance of resveratrol was very high in Wistar and TR, rats (E: 0.998 vs. 0.999; Cl: 34.9 mL/min vs. 36.0 mL/min). However, biliary excretion and efflux of conjugates differs greatly in TR, rats. While cumulative biliary excretion of the glucuronides M1, M2, M3, and M5 dropped dramatically to 0,6%, their efflux into perfusate increased by 3.6-, 1.8-, 2.5-, and 1.5-fold. In contrast, biliary secretion of the sulfates M4 and M6 was partially maintained in the Mrp2-deficient rats (61% and 39%) with a concomitant decline of their efflux into perfusate by 33.2% and 78.1%. This indicates that Mrp2 exclusively mediates the biliary excretion of resveratrol glucuronides but only partly that of sulfates. Cumulative secretion of unconjugated resveratrol into bile of TR, rats was only reduced by 40%, and into perfusate by 19%, suggesting only a minor role of Mrp2 in resveratrol elimination. In summary, resveratrol was dose-dependently metabolized to several conjugates whereby the canalicular transporter Mrp2 selectively mediated the biliary excretion of glucuronides. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:1615,1628, 2008 [source] In Vivo use of the P450 inactivator 1-aminobenzotriazole in the rat: Varied dosing route to elucidate gut and liver contributions to first-pass and systemic clearanceJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2006Timothy J. Strelevitz Abstract The small intestine is regarded as an absorptive organ in the uptake of orally administered drugs, but also has the ability to metabolize drugs by both phase 1 and phase 2 reactions. The amount of drug that reaches the systemic circulation can be reduced by both intestinal and hepatic metabolism. 1-Aminobenzotriazole (ABT) is an irreversible inhibitor of cytochrome P450s. Through in vivo and in vitro studies, ABT has been evaluated for its utility in studying intestinal metabolism in rats. Rats have been exposed to ABT through varied routes of administration followed by p.o. and i.v. administration of midazolam (MDZ), a CYP3A substrate. The MDZ bioavailablity in rats dosed orally and in rats dosed intravenously with ABT is 58.5% and 0.7%, respectively (%F,=,2.3% w/o ABT). The approximately 80-fold difference between the two groups suggests the majority of the extraction occurs in the intestine following an oral dose. To further study the utility of ABT, the antihistamine fexofenadine (Fex), which is not significantly metabolized and is a substrate for the uptake and efflux transporters, OATP and P-gp, was tested in rat. There was no change in oral or systemic exposure of Fex when animals were predosed with ABT, suggesting that ABT does not affect these transporters. These findings may lead to a better understanding of the interdependent role of absorption and metabolism and the specificity of ABT. This method should have utility in drug discovery for the identification of factors limiting oral bioavailability. © 2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 95:1334,1341, 2006 [source] A convenient method for estimating the quantity of drug eliminated by the routes other than hepatic metabolism and renal excretion and the fraction of drug that reaches the "first pass" after oral administrationJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 4 2006Leonid M. Berezhkovskiy Abstract The comparison of routine pharmacokinetic data obtained after intravenous and oral drug administration allows to figure out that some quantity of drug, which reached the systemic circulation, was eliminated from the body by routes other than hepatic metabolism and renal excretion. This quantity is equal or exceeds the certain minimum value, which can be calculated from a simple equation obtained in the article. If the minimum value is equal to zero, then the maximum possible fraction of orally administered drug, that is, absorbed into the gut wall and gets through it unchanged, can be calculated. The examples considered indicate that the quantity of drug eliminated not by liver metabolism or kidney excretion could be quite substantial (exceeds half of the dose that reached the circulation). © 2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 95:828,833, 2006 [source] Exercise Neuroprotection in a Rat Model of Binge Alcohol ConsumptionALCOHOLISM, Issue 3 2010J. Leigh Leasure Background:, Excessive alcohol intake produces structural and functional deficits in corticolimbic pathways that are thought to underlie cognitive deficits in the alcohol use disorders (AUDs). Animal models of binge alcohol administration support the direct link of high levels of alcohol consumption and neurotoxicity in the hippocampus and surrounding cortex. In contrast, voluntary wheel running enhances hippocampal neurogenesis and generally promotes the health of neurons. Methods:, We investigated whether voluntary exercise prior to binge alcohol exposure could protect against alcohol-induced cell loss. Female Long-Evans rats exercised voluntarily for 14 days before undergoing 4 days of binge alcohol consumption. Brains were harvested immediately after the last dose of alcohol and examined for various histological markers of neurodegeneration, including both cell death (FluoroJade B) and cell birth (Ki67) markers. Results:, Rats that exercised prior to binge exposure were significantly less behaviorally intoxicated, which was not a result of enhanced hepatic metabolism. Rats that exercised prior to binge alcohol consumption had reduced loss of dentate gyrus granule cells and fewer FluoroJade B positive cells in the dentate gyrus and associated entorhinal-perirhinal cortex compared to nonexercisers. However, exercise did not protect against cell death in the piriform cortex nor protect against alcohol-induced decreases in cell proliferation, evidenced by a similar alcohol-induced reduction in Ki67 labeled cells between exercise and sedentary rats. Conclusions:, We conclude that exercise can reduce behavioral sensitivity to ethanol intoxication and protect vulnerable brain areas from alcohol-induced cell death. Exercise neuroprotection of alcohol-induced brain damage has important implications in understanding the neurobiology of the AUDs as well as in developing novel treatment strategies. [source] Review article: drug-induced liver injury in clinical practiceALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 1 2010E. Björnsson Aliment Pharmacol Ther 2010; 32: 3,13 Summary Background, Drug-induced liver injury (DILI) is an important differential diagnosis in many patients in clinical hepatology. DILI is the leading cause of acute liver failure and is an important safety issue when new drugs are developed. Aims, To provide a review of the recent data on DILI with particular focus on the most common and relevant issues seen in clinical practice. Methods, A Medline search was undertaken to identify relevant literature using search terms including ,drug-induced liver injury' and ,hepatotoxicity'. Results, The true incidence of DILI remains unknown but incidence up to 14 cases per 100 000 inhabitants and year has been reported. Antibiotics, analgesics and NSAIDs are the most common drugs causing liver injury. Idiosyncratic DILI has been shown to have a dose-dependent component and drugs without significant hepatic metabolism rarely cause DILI. Chronic elevation in liver enzymes can develop after DILI but this is rarely associated with clinical morbidity or mortality. Conclusions, Drug-induced liver injury remains a diagnostic challenge. Multicentre studies and international collaborative work with well-characterized patients will increase our understanding of liver injury associated with drugs. New therapies for acute liver failure resulting from drugs are needed. [source] Quantitative tests of liver function measure hepatic improvement after sustained virological response: results from the HALT-C trialALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 5 2009G. T. EVERSON Summary Backgroud, The impact of virologic response on hepatic function has not been previously defined. Aim, To determine the relationships of quantitative liver function tests (QLFTs) with virological responses to peginterferon (PEG) ± ribavirin (RBV) in patients with chronic hepatitis C and to use serial QLFTs to define the spectrum of hepatic improvement after sustained virological response (SVR). Methods, Participants (n = 232) were enrolled in the Hepatitis C Antiviral Long-term Treatment against Cirrhosis (HALT-C) Trial, had failed prior therapy, had bridging fibrosis or cirrhosis and were retreated with PEG/RBV. All 232 patients had baseline QLFTs; 24 patients with SVR and 68 nonresponders had serial QLFTs. Lidocaine, [24- 13C]cholate, galactose and 99mTc-sulfur colloid were administered intravenously; [2,2,4,2- 2H]cholate, [1- 13C]methionine, caffeine and antipyrine were administered orally. Clearances (Cl), breath 13CO2, monoethylglycylxylidide (MEGX), perfused hepatic mass (PHM) and liver volume were measured. Results, Rates of SVR were 18,26% in patients with good function by QLFTs, but ,6% in patients with poor function. Hepatic metabolism, measured by caffeine kelim (P = 0.02), antipyrine kelim (P = 0.05) and antipyrine Cl (P = 0.02) and the portal circulation, measured by cholate Cloral (P = 0.0002) and cholate shunt (P = 0.0003) and PHM (P = 0.03) improved after SVR. Conclusion, Hepatic dysfunction impairs the virological response to PEG/RBV. SVR improves hepatic metabolism, the portal circulation and PHM. [source] Metabolism of isometamidium in hepatocytes isolated from control and inducer-treated ratsJOURNAL OF VETERINARY PHARMACOLOGY & THERAPEUTICS, Issue 6 2006I. BOIBESSOT Little is known about the metabolism and mechanism of action of the trypanocide, isometamidium (ISM), the major drug used for prophylaxis of trypanosomiasis. We have investigated its metabolism and distribution in isolated rat hepatocytes using liquid chromatography-mass spectrometry and confocal laser scanning microscopy (CLSM). Two putative metabolites were formed, which were proposed to be a mono-acetyl derivative and an oxidized metabolite (SII). This is the first demonstration of the hepatic metabolism of ISM, as previous in vivo studies were hampered by dose-limiting toxicity and insensitive analytical methods. The intrinsic fluorescence of the drug enabled its intracellular uptake to be followed by CLSM. It is taken up rapidly into the nucleolus, nuclear membrane and endoplasmic reticulum within 5 min, and retained in the nucleus for at least 24 h. Persistent binding of ISM to cellular macromolecules may contribute to its prophylactic effect in vivo. Pretreatment of rats with 3-methylcholanthrene, phenobarbitone (PB) or the widely used pyrethroid pesticide, deltamethrin, resulted in an increase in metabolism of ISM to the proposed SII after 1 h incubation with hepatocytes. 3-methylcholanthrene was the most potent inducer, causing a maximal 19.5-fold induction of SII formation after exposure of hepatocytes to ISM for 1 h compared with formation by control hepatocytes. In comparison, at the 1 h timepoint deltamethrin pre-treatment caused a 10.2-fold induction, and PB only 8.2 fold. [source] KN07 Extra hepatic metabolism of xenobiotics, focusing on veterinary speciesJOURNAL OF VETERINARY PHARMACOLOGY & THERAPEUTICS, Issue 2006H. TJÄLVE First page of article [source] Vitamin E and K interactions , a 50-year-old problemNUTRITION REVIEWS, Issue 11 2008Maret G Traber The mechanisms by which vitamin E interferes with vitamin K activity, especially blood clotting, are not known, but hypothetically this interference may involve metabolic pathways. Phylloquinone (K1) must be converted to menaquinone (MK-4, the most potent extrahepatic tissue vitamin K) by truncation of the K1 side chain and replacement with geranylgeranyl. Possible mechanisms for the vitamin E and K interaction include: 1) vitamin E competes for the yet undiscovered enzyme that truncates the K1 side chain; 2) vitamin E competes with K1 for the hypothetical cytochrome P450 enzyme that ,-hydroxylates the K1 side chain, thereby preventing its ,-oxidation and its removal for MK-4 formation; or 3) vitamin E increases xenobiotic pathways that increase hepatic metabolism and excretion of all vitamin K forms. Currently, the pathway for K1 conversion to MK-4 is unknown, the process for regulating vitamin K metabolism to urinary excretion products is unknown, and why vitamin E supplements have such a dramatic effect, causing bleeding in some individuals and not in others, remains a mystery. [source] Dietary Fructose: Implications for Dysregulation of Energy Homeostasis and Lipid/Carbohydrate MetabolismNUTRITION REVIEWS, Issue 5 2005Peter J. Havel DVM Fructose intake and the prevalence of obesity have both increased over the past two to three decades. Compared with glucose, the hepatic metabolism of fructose favors lipogenesis, which may contribute to hyperlipidemia and obesity. Fructose does not increase insulin and leptin or suppress ghrelin, which suggests an endocrine mechanism by which it induces a positive energy balance. This review examines the available data on the effects of dietary fructose on energy homeostasis and lipid/carbohydrate metabolism. Recent publications, studies in human subjects, and areas in which additional research is needed are emphasized. [source] Prediction of herb,drug metabolic interactions: a simulation studyPHYTOTHERAPY RESEARCH, Issue 6 2005Shufeng Zhou Abstract In vitro and in vivo studies have indicated that the induction or inhibition of cytochrome P450 (CYP) is one of the major mechanisms for some clinically important pharmacokinetic herb,drug interactions. An attempt was made to simulate the effects of herbal preparation with single or multiple CYP-inhibiting constituents on the area of the plasma concentration-time curve (AUC) of coadministered drug that was either a low clearance drug by intravenous (i.v.) injection or a high clearance drug by oral route. Our simulation studies indicated that the expected increase (Rc) in the AUC of the coadministered drug by inhibiting herbal constituent(s) was dependent on the route of administration. For low clearance drug by i.v. injection, Rc was generally determined by inhibition constant (Ki), unbound inhibitor concentration ([I]), hepatic fraction (fh), number of inhibitory herbal constituents (n) and metabolic pathway fraction in hepatic metabolism (fm), while Rc for a high clearance drug by oral route, Rc was determined by Ki, [I], n and fm. By varying these parameters, Rc changed accordingly. It appeared likely to predict a herb,drug metabolic interaction, if the inhibiting herbal constituents could be quantitatively determined. However, many herb- and drug-related factors may cause difficulties with the prediction, and thus in vivo animal and human studies are always necessary. Copyright © 2005 John Wiley & Sons, Ltd. [source] Latest news and product developmentsPRESCRIBER, Issue 22 2007Article first published online: 28 DEC 200 Glitazones: benefits outweigh the risks Following a review of the safety of rosiglitazone and pioglitazone, the European Medicines Agency (EMEA) has concluded that their benefits outweigh their risks in the approved indications. The review was prompted by reports of an increased risk of fractures in women and, in patients taking rosiglitazone, ischaemic heart disease. The EMEA concluded that prescribing information for rosiglitazone should now include a warning that, in patients with ischaemic heart disease, it should only be used after careful evaluation of each patient's individual risk, and the combination of rosiglitazone and insulin should only be used in exceptional cases and under close supervision. No change was considered necessary to the prescribing information for pioglitazone. Modern dressings no better? A systematic review has found only weak evidence that modern dressings are better than saline gauze or paraffin gauze for healing acute and chronic wounds (Arch Dermatol 2007;143: 1297-304). The analysis, which included 99 studies, found that only hydrocolloids were demonstrably better than older dressings for healing chronic wounds, and alginates were superior to other modern dressings for debriding necrotic wounds. There was no evidence that modern dressings offered superior overall performance to the older alternatives. Hospital inflation twice primary care level The cost of drugs prescribed in secondary care but dispensed in the community increased by 6.4 per cent in 2006 - twice the rate of inflation in primary care - according to the latest statistics on hospital prescribing in England. The increase follows a reduction in costs in 2005 after the introduction of the new PPRS scheme. Data from The Information Centre (www.ic.nhs.uk) show that hospital medicines make up about 24 per cent of the NHS drugs budget. Secondary care has a consistently better record than primary care in prescribing lower-cost alternatives within therapeutic categories, eg simvastatin and pravastatin among the statins, omeprazole and lansoprazole among PPIs, and ACE inhibitors among drugs acting on the renin angiotensin system. The most expensive drug prescribed by hospital specialists and dispensed in the community is interferon beta. MHRA limits the use of fibrates The Medicines and Healthcare products Regulatory Agency (MHRA) has advised that fibrates should now be reserved for the treatment of isolated severe hypertriglyceridaemia. They should be considered for hypercholesterolaemia only when a statin or other treatment is contraindicated or not tolerated. In the latest Drug Safety Update, the MHRA says there is insufficient evidence of long-term benefits from fibrates, and first-line use is no longer justified because the evidence for the benefits of statins is robust. The MHRA also warns that some breastfeeding infants have increased susceptibility to the adverse effects of codeine taken by their mother, and that St John's wort may affect the hepatic metabolism of any anticonvulsant. Annual zoledronic acid infusion cuts mortality after hip fracture Once-yearly infusion of zoledronic acid (Aclasta) after hip fracture reduces deaths over a two-year period by 28 per cent compared with placebo, US investigators say (N Engl J Med 2007;357:1799-809). The HORIZON Recurrent Fracture Trial randomised 2127 men and women (mean age 75) within 90 days of surgery for hip fracture to zoledronic acid 5mg yearly or placebo. Mortality over 1.9 years of follow-up was 9.6 per cent with zoledronic acid and 13.3 per cent with placebo. Zoledronic acid also significantly reduced the rate of any new clinical fractures (by 35 per cent) and new clinical vertebral fractures(by 45 per cent),but the lower rate of hip fracture (2.0 vs 3.5 per cent with placebo) was not statistically significant. Rivastigmine patch for mild to moderate AD Rivastigmine (Exelon) is now available as a transdermal patch for the treatment of mild to moderate Alzheimer's disease. Applied once daily, the patch delivers 9.5mg per 24 hours and, says manufacturer Novartis, is associated with a lower incidence of nausea and vomiting than a comparable oral dose. The patch is available in two strengths: 4.6mg per 24hr is equivalent to oral doses of 3 or 6mg per day, and the 9.5mg per 24hr patch is equivalent to 9 or 12mg per day orally. The recommended dose of the patch is 9.5mg per day; both strengths cost £83.84 for 30 patches. Women more aspirin resistant than men? The cardioprotective effect of low-dose aspirin may be lower in women than men, say Canadian investigators (BMC Medicine 2007;5:29 doi: 10.1186/1741-70155-29). Their meta-analysis of 23 randomised trials involving a total of 113 494 participants found that aspirin significantly reduced the risk of nonfatal but not fatal myocardial infarction (MI). About one-quarter of the variation in its effects on nonfatal MI was accounted for by the sex mix of the trial population. Separating the results by sex showed the reduction in risk with aspirin use was statistically significant in men (relative risk, RR, 0.62) but not in women (RR 0.87). Look after physical health of mentally ill GPs and other primary care workers should take more responsibility for the physical health of their mentally ill patients, say advocacy groups. Mind and Body: Preventing and Improving Physical Health Problems in Patients With Schizophrenia points out that the mental health needs of patients with schizophrenia are met in secondary care, but their physical health needs should be met in primary care. In particular, the metabolic effects of antipsychotics may lead to obesity, diabetes and cardiovascular disease, and weight gain in particular is a frequent reason for nonadherence to treatment. The Mind and Body Manifesto was developed by SANE, The Mental Health Nurses Association, The National Obesity Forum and The Disability Rights Commission and sponsored by Bristol-Myers Squibb Pharmaceuticals Limited and Otsuka Pharmaceuticals (UK) Ltd. Copies are available from elizabeth.green@ ogilvyhealthworld.com. Health eCard costs Some costs quoted in our article on the Health eCard (The Health eCard: the way ahead for medical records?,5 October issue, pages 28-9) have been revised: the card and initial download will cost patients £39.50, and GPs will be entitled to charge patients £10 per annum for subsequent downloads. NICE appraisals of cytokine inhibitors in RA NICE has endorsed the use of the anti-TNF agents adalimumab (Humira), etanercept (Enbrel) and infliximab (Remicade), normally in conjunction with methotrexate, for the treatment of active RA when methotrexate and another DMARD have failed (also see New from NICE below). NICE has provisionally concluded, subject to consultation, that abatacept (Orencia) should not be recommended for the treatment of RA. Boots and BMJ launch health advice site www.askbootshealth.com is a new website providing information about health and medicines for the public produced by Boots using information provided by the BMJ Publishing Group. The website covers many of the topics already available from NHSDirect, with perhaps more information about available treatments. Diabetes care shows small improvement The third National Diabetes Audit in England and Wales has found that more people with diabetes were achieving the targets set by NICE for cholesterol levels, glycaemic control and blood pressure in 2005/06 - but younger patients were doing less well. Overall, the HbA1C target of ,7.5 per cent was achieved in 60 per cent of people with diabetes compared with 58 per cent in 2004/05. However, HbA1C was >9.5 per cent in 30 per cent of children and young people, of whom 9 per cent experienced at least one episode of ketoacidosis. More topics for NICE New topics referred to NICE include clinical guidelines on ovarian cancer, coeliac disease and stable angina, public health guidance on preventing cardiovascular disease, and technology appraisals on insulin detemir (Levemir) for type 1 diabetes, several treatments for cancer and hepatic and haematological disorders, and biological therapies for juvenile arthritis. New from NICE NICE appraisal on anti-TNFs for RA Since NICE published its first appraisal of agents acting against tumour necrosis factor-alpha (anti-TNFs) for the treatment of RA in 2002, the product licences for etanercept (Enbrel) and infliximab (Remicade) have changed and a new agent, adalimumab (Humira), has been introduced. The anti-TNFs act in different ways. Infliximab is a chimeric monoclonal antibody that binds to TNF-alpha, neutralising its activity. Etanercept, a recombinant human TNF-alpha receptor fusion protein, and adalimumab, a human-sequence antibody, both bind to TNF-alpha and block its interaction with cell surface receptors. Adalimumab also modulates some biological responses induced or regulated by TNF-alpha. These agents are recommended for adults with severe active RA (defined as a disease activity score - DAS28 - greater than 5.1) who have already tried two disease-modifying drugs, including methotrexate (if not contraindicated). Prior treatment should have been of at least six months' duration, including two months at the standard dose (unless limited by toxicity). Anti-TNFs should normally be prescribed with methotrexate; when this is not appropriate, etanercept and adalimumab may be prescribed as monotherapy. Treatment with an anti-TNF should be continued beyond six months only if there is an adequate response (defined as an improvement in DAS28 of at least 1.2). Data from the British Rheumatology Society Biologics register show that, after six months, 67 per cent of patients met NICE criteria for an adequate response; this declined to 55 per cent at 18 months. The basic annual cost of treatment is £9295 for adalimumab 40mg on alternate weeks or etanercept 25mg twice weekly; infliximab costs £3777 for a loading dose, then £7553-£8812 depending on dose. Assuming no progression of disability, the incremental costs per QALY (compared with sequential DMARDs) were £30 200 for adalimumab, £24 600 for etanercept and £39 400 for infliximab. There are no direct comparative trials of the anti-TNFs, and their clinical trial findings are not directly comparable. Unless other factors determine treatment choice, NICE therefore recommends the least expensive. If the first anti-TNF is withdrawn within six months due to an adverse event, a second may be tried. [source] Intestinal and hepatic metabolism of glutamine and citrulline in humansTHE JOURNAL OF PHYSIOLOGY, Issue 2 2007Marcel C. G. Van De Poll Glutamine plays an important role in nitrogen homeostasis and intestinal substrate supply. It has been suggested that glutamine is a precursor for arginine through an intestinal,renal pathway involving inter-organ transport of citrulline. The importance of intestinal glutamine metabolism for endogenous arginine synthesis in humans, however, has remained unaddressed. The aim of this study was to investigate the intestinal conversion of glutamine to citrulline and the effect of the liver on splanchnic citrulline metabolism in humans. Eight patients undergoing upper gastrointestinal surgery received a primed continuous intravenous infusion of [2- 15N]glutamine and [ureido- 13C,2H2]citrulline. Arterial, portal venous and hepatic venous blood were sampled and portal and hepatic blood flows were measured. Organ specific amino acid uptake (disposal), production and net balance, as well as whole body rates of plasma appearance were calculated according to established methods. The intestines consumed glutamine at a rate that was dependent on glutamine supply. Approximately 13% of glutamine taken up by the intestines was converted to citrulline. Quantitatively glutamine was the only important precursor for intestinal citrulline release. Both glutamine and citrulline were consumed and produced by the liver, but net hepatic flux of both amino acids was not significantly different from zero. Plasma glutamine was the precursor of 80% of plasma citrulline and plasma citrulline in turn was the precursor of 10% of plasma arginine. In conclusion, glutamine is an important precursor for the synthesis of arginine after intestinal conversion to citrulline in humans. [source] Unique Early Gene Expression Patterns in Human Adult-to-Adult Living Donor Liver Grafts Compared to Deceased Donor GraftsAMERICAN JOURNAL OF TRANSPLANTATION, Issue 4 2009J. De Jonge Because of inherent differences between deceased donor (DD) and living donor (LD) liver grafts, we hypothesize that the molecular signatures will be unique, correlating with specific biologic pathways and clinical patterns. Microarray profiles of 63 biopsies in 13 DD and 8 LD liver grafts done at serial time points (procurement, backbench and postreperfusion) were compared between groups using class comparisons, network and biological function analyses. Specific genes were validated by quantitative PCR and immunopathology. Clinical findings were also compared. Following reperfusion, 579 genes in DD grafts and 1324 genes in LDs were differentially expressed (p < 0.005). Many upregulated LD genes were related to regeneration, biosynthesis and cell cycle, and a large number of downregulated genes were linked to hepatic metabolism and energy pathways correlating with posttransplant clinical laboratory findings. There was significant upregulation of inflammatory/immune genes in both DD and LD, each with a distinct pattern. Gene expression patterns of select genes associated with inflammation and regeneration in LD and DD grafts correlated with protein expression. Unique patterns of early gene expression are seen in LD and DD liver grafts, correlating with protein expression and clinical results, demonstrating distinct inflammatory profiles and significant downregulation of metabolic pathways in LD grafts. [source] In vitro Metabolism of Genistein and Tangeretin by Human and Murine Cytochrome P450sBASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 1 2003Vibeke M. Breinholt Analysis of the metabolic profile from incubations with genistein and human liver microsomes revealed the production of five different metabolites, of which three were obtained in sufficient amounts to allow a more detailed elucidation of the structure. One of these metabolites was identified as orobol, the 3,-hydroxylated metabolite of genistein. The remaining two metabolites were also hydroxylated metabolites as evidenced by LC/MS. Orobol was the only metabolite formed after incubation with CYP1A2. The two major product peaks after incubation of tangeretin with human microsomes were identical with 4,-hydroxy-5,6,7,8-tetramethoxyflavone and 5,6-dihydroxy-4,,7,8-trimethoxyflavone, previously identified in rat urine in our laboratory. By comparison with UV spectra and LC/MS fragmentation patterns of previously obtained standards, the remaining metabolites eluting after 14, 17 and 20 min. were found to be demethylated at the 4,,7-, 4,,6-positions or hydroxylated at the 3,- and demethylated at the 4,-positions, respectively. Metabolism of tangeretin by recombinant CYP1A2, 3A4, 2D6 and 2C9 resulted in metabolic profiles that qualitatively were identical to those observed in the human microsomes. Inclusion of the CYP1A2 inhibitor fluvoxamine in the incubation mixture with human liver microsomes resulted in potent inhibition of tangeretin and genistein metabolism. Other isozymes-selective CYP inhibitors had only minor effects on tangeretin or genistein metabolism. Overall the presented observations suggest major involvement of CYP1A2 in the hepatic metabolism of these two flavonoids. [source] Ipriflavone pharmacokinetics in mutant Nagase analbuminemic ratsBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 6 2009Hye J. Chung Abstract Ipriflavone, a derivative of naturally occurring isoflavones, was primarily metabolized in rats via hepatic CYP1A1/2 and 2C11. Protein and mRNA expression of CYP1A2 in the liver, reported to be increased in mutant Nagase analbuminemic rats (NARs), should influence the pharmacokinetic parameters of ipriflavone. In this study, the contribution of hepatic CYP2C11 and intestinal CYP1A protein to the metabolism and the pharmacokinetic parameters of ipriflavone were examined after intravenous (20,mg/kg) and oral (200,mg/kg) administration to male Sprague,Dawley (control) rats and NARs. There was no change in the protein expression of hepatic CYP2C11. By contrast, CYP1A protein of the intestine increased by almost 100%. After the intravenous administration of ipriflavone to NARs, the Clnr and AUC were unchanged, suggesting that the contribution of the increase in protein expression and mRNA level of hepatic CYP1A2 to hepatic metabolism of the drug in NARs seemed to be almost negligible. However, after the oral administration of ipriflavone to NARs, the AUC was significantly lower than that in the control rats (53.0% decrease), possibly due to the increased intestinal CYP1A that resulted in increased intestinal metabolism and decreased gastrointestinal absorption of ipriflavone in NARs. Copyright © 2009 John Wiley & Sons, Ltd. [source] Dose-dependent pharmacokinetics and first-pass effects of mirodenafil, a new erectogenic, in ratsBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 6 2009Young H. Choi Abstract The pharmacokinetics of mirodenafil and its two metabolites, SK3541 and SK3544, after intravenous (5, 10, 20 and 50,mg/kg) and oral (10, 20 and 50,mg/kg) administration of mirodenafil, and the first-pass effect of mirodenafil after intravenous, oral, intraportal, intragastric and intraduodenal (20,mg/kg) administration of mirodenafil were evaluated in rats. The pharmacokinetics of mirodenafil and SK3541 were dose-dependent after both intravenous and oral administration of mirodenafil due to the saturable hepatic metabolism of mirodenafil. After oral administration of mirodenafil, approximately 2.59% of the oral dose was not absorbed, the F value was approximately 29.4%, and the hepatic and gastrointestinal first-pass effects of mirodenafil were approximately 21.4% and 54.3% of the oral dose, respectively. The low F value of mirodenafil in rats was mainly due to considerable hepatic and gastrointestinal first-pass effects in rats. The equilibrium plasma-to-blood cell partition ratios of mirodenafil were independent of the initial blood mirodenafil concentrations of 1,10,µg/ml; the mean values were 1.08,1.21. The plasma binding values of mirodenafil to rat plasma was 87.8%. Copyright © 2009 John Wiley & Sons, Ltd. [source] Faster clearance of omeprazole in mutant Nagase analbuminemic rats: possible roles of increased protein expression of hepatic CYP1A2 and lower plasma protein bindingBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 3 2009Dae Y. Lee Abstract It is well known that there are various changes in the expression of hepatic and intestinal CYPs in mutant Nagase analbuminemic rats (NARs). It has been reported that the protein expression of hepatic CYP1A2 was increased, whereas that of hepatic CYP3A1 was not altered, and it was also found that the protein expression of the intestinal CYP1A subfamily significantly increased in NARs from our other study. In addition, in this study additional information about CYP changes in NARs was obtained; the protein expression of the hepatic CYP2D subfamily was not altered, but that of the intestinal CYP3A subfamily increased in NARs. Because omeprazole is metabolized via hepatic CYP1A1/2, 2D1, 3A1/2 in rats, it could be expected that the pharmacokinetics of omeprazole would be altered in NARs. After intravenous administration of omeprazole to NARs, the Clnr was significantly faster than in the controls (110 versus 46.6 ml/min/kg), and this could be due to an increase in hepatic metabolism caused by a greater hepatic CYP1A2 level in addition to greater free fractions of the drug in NARs. After oral administration of omeprazole to NARs, the AUC was also significantly smaller (80.1% decrease) and F was decreased in NARs. This could be primarily due to increased hepatic and intestinal metabolism caused by greater hepatic CYP1A2 and intestinal CYP1A and 3A levels. In particular, the smaller F could mainly result from greater hepatic and intestinal first-pass effect in NARs than in the controls. Copyright © 2009 John Wiley & Sons, Ltd. [source] Gender differences in ondansetron pharmacokinetics in ratsBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 7 2008Si H. Yang Abstract It has been reported that ondansetron is primarily metabolized via hepatic CYP2D and 3A1/2 in male Sprague,Dawley rats, and CYP2D1 and 3A2 are male dominant and male specific isozymes, respectively, in rats. Thus, it could be expected that the pharmacokinetics of ondansetron would be changed in male rats compared with those in female rats. Thus, gender-different ondansetron pharmacokinetics were evaluated after its intravenous or oral administration at a dose of 8 mg/kg to male and female Sprague,Dawley rats. After intravenous administration of ondansetron to male rats, the AUC and time-averaged non-renal clearance (Clnr) of the drug were significantly smaller (22.6% decrease) and faster (27.3% increase), respectively, than those in female rats. This probably could be due to faster hepatic blood flow rate in male rats. After oral administration of ondansetron to male rats, the AUC of the drug was also significantly smaller (58.8% decrease) than that in female rats, and this could have been due mainly to increased intestinal metabolism of ondansetron in addition to increased hepatic metabolism of the drug in male rats. Copyright © 2008 John Wiley & Sons, Ltd. [source] Pharmacokinetics of omeprazole in rats with water deprivation for 72 hoursBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 8 2006Dae Y. Lee Abstract Dehydration can occur by excessive sweating, polyuria, severe diarrhea and hyperthermia. Previous studies reported that the expressions of CYP1A1/2 and 3A1(23)/2 were not changed in male Sprague,Dawley rats with 72 h water deprivation (dehydrated rats), and that the metabolism of omeprazole is mainly catalysed via CYP1A1/2, 2D1 and 3A23/2 in rats. Hence, it could be expected that the hepatic metabolism of omeprazole would not be changed considerably in dehydrated rats, if the contribution of CYP2D1 to the metabolism of omeprazole in dehydrated rats is not considerable. Therefore, the pharmacokinetics of omeprazole were compared after intravenous (20 mg/kg) and oral (40 mg/kg) administration in control rats and in dehydrated rats. After intravenous administration, the time-averaged nonrenal clearance (Clnr) values of omeprazole were comparable between the two groups of rats. This could be supported by comparable in vitro intrinsic clearance (Clint) values for the disappearance of omeprazole in rat hepatic microsomes and the comparable free (unbound to plasma proteins) fractions of omeprazole in plasma in the two groups of rats. After oral administration, the AUC values of omeprazole were also comparable in the two groups of rats. The above data suggest that the dehydration state did not affect considerably the pharmacokinetics of omeprazole in rats. Copyright © 2006 John Wiley & Sons, Ltd. [source] Minimal effect of ketoconazole on cyclosporine (SangCyATM) oral absorption and first-pass metabolism in rats: evidence of a significant vehicle effect on SangCyA absorptionBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 2 2002Susan Wong Abstract The current work evaluated the effect of the CYP3A inhibitor ketoconazole on the oral absorption and first-pass metabolism of cyclosporine administered as the SangCyA formulation. Groups of 6 male Sprague,Dawley rats were administered SangCyA (5 and 15 mg/kg) by oral gavage alone and with ketoconazole (30 mg/kg). Blood cyclosporine levels were measured over 6 h, encompassing the cyclosporine absorption window. A significant vehicle effect on SangCyA absorption was observed. Comparing a 15 mg/kg dose, cyclosporine Cmax (mean±SD 1.12±0.16 µg/ml) and AUC0,6 (5.34±0.71 µg h/ml) were 50% lower when propylene glycol was used as gavage vehicle instead of saline (2.19±0.94 µg/ml and 9.52±2.52 µg h/ml, respectively). Coefficients-of-variation for these parameters were halved in the propylene glycol vehicle however Tmax was unaffected. Ketoconazole increased cyclosporine Cmax and AUC0,6 by 50,60%, regardless of the vehicle or the cyclosporine dose, without altering Tmax (2,3 h). The small effect of ketoconazole suggests that CYP3A-mediated intestinal and first-pass hepatic metabolism are minor determinants of cyclosporine oral bioavailability in rats. Copyright © 2002 John Wiley & Sons, Ltd. [source] | |||||||||||||