Effect of pterostilbene on in vitro drug metabolizing enzyme activity.

Pterostilbene is a natural polyphenol compound found in small berries that is related to resveratrol, but has better bioavailability and a longer half-life. The purpose of this study was to assess the potential inhibitory effect of pterostilbene on in vitro drug metabolism. The effect of pterostilbene on cytochrome P450 (CYP) and UDP-glucuronosyltransferase (UGT) enzyme activities were studied using the enzyme-selective substrates amodiaquine (CYP2C8), midazolam (CYP3A4), estradiol (UGT1A1), serotonin (UGT1A6) and mycophenolic acid (UGT1A8/9/10). The IC50 value was used to express the strength of inhibition. Further, a volume per dose index (VDI) was used to estimate the potential for in vivo interactions. Pterostilbene significantly inhibited CYP2C8 and UGT1A6 activities. The IC50 (mean ±â€¯SE) values for CYP2C8 and UGT1A6 inhibition were 3.0 ±â€¯0.4 µM and 15.1 ±â€¯2.8 µM, respectively; the VDI exceeded the predefined threshold of 5 L/dose for both CYP2C8 and UGT1A6, suggesting a potential for interaction in vivo. Pterostilbene did not inhibit the metabolism of the other enzyme-selective substrates. The results of this study indicate that pterostilbene inhibits CYP2C8 and UTG1A6 activity in vitro and may inhibit metabolism by these enzymes in vivo. Clinical studies are warranted to evaluate the in vivo relevance of these interactions.

Pioglitazone improves hepatic mitochondrial function in a mouse model of nonalcoholic steatohepatitis.

Pioglitazone is effective in improving insulin resistance and liver histology in patients with nonalcoholic steatohepatitis (NASH). Because dysfunctional mitochondrial metabolism is a central feature of NASH, we hypothesized that an important target of pioglitazone would be alleviating mitochondrial oxidative dysfunction. To this end, we studied hepatic mitochondrial metabolism in mice fed high-fructose high-transfat diet (TFD) supplemented with pioglitazone for 20 wk, using nuclear magnetic resonance-based 13C isotopomer analysis. Pioglitazone improved whole body and adipose insulin sensitivity in TFD-fed mice. Furthermore, pioglitazone reduced intrahepatic triglyceride content and fed plasma ketones and hepatic TCA cycle flux, anaplerosis, and pyruvate cycling in mice with NASH. This was associated with a marked reduction in most intrahepatic diacylglycerol classes and, to a lesser extent, some ceramide species (C22:1, C23:0). Considering the cross-talk between mitochondrial function and branched-chain amino acid (BCAA) metabolism, pioglitazone's impact on plasma BCAA profile was determined in a cohort of human subjects. Pioglitazone improved the plasma BCAA concentration profile in patients with NASH. This appeared to be related to an improvement in BCAA degradation in multiple tissues. These results provide evidence that pioglitazone-induced changes in NASH are related to improvements in hepatic mitochondrial oxidative dysfunction and changes in whole body BCAA metabolism.

Pharmacogenomics competencies in pharmacy practice: A blueprint for change.

The emerging use of genomic data to inform medication therapy populates the medical literature and provides evidence for guidelines in the prescribing information for many medications. Despite the availability of pharmacogenomic studies, few pharmacists feel competent to use these new data in patient care. The first pharmacogenomics competency statement for pharmacists was published in 2002. In 2011, the Pharmacogenomics Special Interest Group of the American Association of Colleges of Pharmacy led a process to update this competency statement with the use of a consensus-based method that incorporated input from multiple key professional pharmacy organizations to reflect growth in genomic science as well as the need for pharmacist application of genomic data. Given the rapidly evolving science, educational needs, and practice models in this area, a standardized competency-based approach to pharmacist education and training in pharmacogenomics is needed to equip pharmacists for leadership roles as essential members of health care teams that implement clinical utilization strategies for genomic data.

Inhibitory effect of six herbal extracts on CYP2C8 enzyme activity in human liver microsomes.

1. Herbal supplements widely used in the US were screened for the potential to inhibit CYP2C8 activity in human liver microsomes. The herbal extracts screened were garlic, echinacea, saw palmetto, valerian, black cohosh and cranberry. N-desethylamodiaquine (DEAQ) and hydroxypioglitazone metabolite formation were used as indices of CYP2C8 activity. 2. All herbal extracts showed inhibition of CYP2C8 activity for at least one of three concentrations tested. A volume per dose index (VDI) was calculated to determine the volume in which a dose should be diluted to obtain IC50 equivalent concentration. Cranberry and saw palmetto had a VDI value > 5.0 l per dose unit, suggesting a potential for interaction. 3. Inhibition curves were constructed and the IC50 (mean ± SE) values were 24.7 ± 2.7 µg/ml for cranberry and 15.4 ± 1.7 µg/ml for saw palmetto. 4. The results suggest a potential for cranberry or saw palmetto extracts to inhibit CYP2C8 activity. Clinical studies are needed to evaluate the significance of this interaction.

The effects of milk thistle (Silybum marianum) on human cytochrome P450 activity.

Milk thistle (Silybum marianum) extracts are widely used as a complementary and alternative treatment of various hepatic conditions and a host of other diseases/disorders. The active constituents of milk thistle supplements are believed to be the flavonolignans contained within the extracts. In vitro studies have suggested that some milk thistle components may significantly inhibit specific cytochrome P450 (P450) enzymes. However, determining the potential for clinically significant drug interactions with milk thistle products has been complicated by inconsistencies between in vitro and in vivo study results. The aim of the present study was to determine the effect of a standardized milk thistle supplement on major P450 drug-metabolizing enzymes after a 14-day exposure period. CYP1A2, CYP2C9, CYP2D6, and CYP3A4/5 activities were measured by simultaneously administering the four probe drugs, caffeine, tolbutamide, dextromethorphan, and midazolam, to nine healthy volunteers before and after exposure to a standardized milk thistle extract given thrice daily for 14 days. The three most abundant falvonolignans found in plasma, following exposure to milk thistle extracts, were silybin A, silybin B, and isosilybin B. The concentrations of these three major constituents were individually measured in study subjects as potential perpetrators. The peak concentrations and areas under the time-concentration curves of the four probe drugs were determined with the milk thistle administration. Exposure to milk thistle extract produced no significant influence on CYP1A2, CYP2C9, CYP2D6, or CYP3A4/5 activities.

Insulin resistance is an integral feature of MASLD even in the presence of PNPLA3 variants.

Background & Aims: It has been postulated that carriers of PNPLA3 I148M (CG [Ile/Met] or GG [Met/Met]) develop metabolic dysfunction-associated steatotic liver disease (MASLD) in the absence of insulin resistance or metabolic syndrome. However, the relationship between insulin resistance and MASLD according to the PNPLA3 allele has not been carefully assessed. Methods: A total of 204 participants were recruited and underwent PNPLA3 genotyping, an oral glucose tolerance test, liver proton magnetic resonance spectroscopy and percutaneous liver biopsy if diagnosed with MASLD. A subgroup of patients (n = 55) had an euglycemic hyperinsulinemic clamp with glucose tracer infusion. Results: As expected, patients with the CG/GG genotype had worse intrahepatic triglyceride content and worse liver histology. However, regardless of PNPLA3 genotype, patients with a diagnosis of MASLD had severe whole-body insulin resistance (Matsuda index, an estimation of insulin resistance in glucose metabolic pathways) and fasting and postprandial adipose tissue insulin resistance (Adipo-IR index and free fatty acid suppression during the oral glucose tolerance test, respectively, as measures of insulin resistance in lipolytic metabolic pathways) compared to patients without MASLD. Moreover, for the same amount of liver fat accumulation, insulin resistance was similar in patients with genotypes CC vs. CG/GG. In multiple regression analyses, A1c and Adipo-IR were associated with the presence of MASLD and advanced liver fibrosis, independently of PNPLA3 genotype. Conclusions: PNPLA3 variant carriers with MASLD are equally insulin resistant as non-carriers with MASLD at the level of the liver, muscle, and adipose tissue. This calls for reframing "PNPLA3 MASLD" as an insulin-resistant condition associated with increased hepatic susceptibility to metabolic insults, such as obesity or diabetes, wherein early identification and aggressive intervention are warranted to reverse metabolic dysfunction and prevent disease progression. Impact and implications: It has been proposed that the PNPLA3 G allele is associated with the presence of metabolic dysfunction-associated steatotic liver disease (MASLD) in the absence of insulin resistance. However, our results suggest that regardless of PNPLA3 alleles, the presence of insulin resistance is necessary for the development of MASLD. This calls for reframing patients with "PNPLA3 MASLD" not as insulin sensitive, but on the contrary, as an insulin-resistant population with increased hepatic susceptibility to metabolic insults, such as obesity or diabetes.

Pharmacokinetic properties of pure xanthones in comparison to a mangosteen fruit extract in rats.

The xanthones α-mangostin and γ-mangostin are the major bioactive compounds in Garcinia mangostana (mangosteen) fruit extracts. Previously, we reported the pharmacokinetic properties of α-mangostin in rats. The purpose of this follow-up study was to compare the pharmacokinetic characteristics of α-mangostin and γ-mangostin in rats if administered as either a pure compound or as a component of a mangosteen fruit extract. The absolute bioavailability of γ-mangostin when administered as a pure compound was determined by giving male Sprague Dawley rats 2 mg/kg γ-mangostin intravenously or 20 mg/kg orally. A 160 mg/kg aliquot of mangosteen fruit extract was administered, containing α- and γ-mangostin doses equal to 20 mg/kg and 4.5 mg/kg of each pure compound, respectively. Plasma samples were collected for both pharmacokinetic studies, and compound concentrations were measured by LC-MS/MS. The pharmacokinetic of γ-mangostin after intravenous administration followed a two-compartment body model. The half-life of the distribution phase was 2.40 min, and that of the elimination phase was 1.52 h. After oral administration, both α- and γ-mangostin underwent intensive first-pass metabolism, and both compounds were conjugated rapidly after oral administration. When given as an extract, the total absorption of α- and γ-mangostin was not increased, but the conjugation was slower, resulting in increased free (unconjugated) compound exposure when compared to pure compound administration. Since reported beneficial biological activities of mangosteen xanthones are based on the free, unconjugated compounds, food supplements containing mangosteen fruit extracts should be preferred over the administration of pure xanthones.

Cyclophosphamide and 4-hydroxycyclophosphamide pharmacokinetics in patients with glomerulonephritis secondary to lupus and small vessel vasculitis.

AIMS: Cyclophosphamide, the precursor to the active 4-hydroxycyclophosphamide, is used in active glomerulonephritis despite limited pharmacokinetics data. The pharmacokinetics of cyclophosphamide and 4-hydroxycyclophosphamide were evaluated. The influence of laboratory and pharmacogenomic covariates on pharmacokinetics was evaluated as a secondary aim. METHODS: Glomerulonephritis patients (n = 23) participated in a pharmacokinetic evaluation. Blood was serially collected and assayed for cyclophosphamide and 4-hydroxycyclophosphamide by LC/MS methods. Kidney function, serum albumin and polymorphisms in drug metabolism or transport genes were evaluated. Analyses included non-compartmental pharmacokinetics and parametric and non-parametric statistics. RESULTS: The mean area under the plasma concentration-time curve (AUC(0,∞)) data were 110,100 ± 42,900 ng ml(-1) h and 5388 ± 2841 ng ml(-1) h for cyclophosphamide and 4-hydroxycyclophosphamide, respectively. The mean metabolic ratio was 0.06 ± 0.04. A statistically significant relationship was found between increased serum albumin and increased half-life (0.584, P = 0.007, 95% CI 0.176, 0.820) and a borderline relationship with AUC(0,∞) (0.402, P = 0.079, 95% CI -0.064, 0.724) for 4-hydroxycyclophosphamide. Covariate relationships that trended toward significance for cyclophosphamide included decreased serum albumin and increased elimination rate constant (-0.427, P = 0.061, 95% CI 0.738, 0.034), increased urinary protein excretion and increased AUC(0,∞) (-0.392, P = 0.064, 95% CI -0.699 to 0.037), decreased C(max) (0.367, P = 0.085, 95% CI -0.067, 0.684) and decreased plasma clearance (-0.392, P = 0.064, 95% CI -0.699, 0.037). CYP2B6*9 variants vs. wildtype were found to have decreased elimination rate constant (P = 0.0005, 95% CI 0.033, 0.103), increased V(d) (P = 0.0271, 95% CI -57.5, -4.2) and decreased C(max) (P = 0.0176, 95% CI 0.696, 6179) for cyclophosphamide. ABCB1 C3435T variants had a borderline decrease in cyclophosphamide elimination rate constant (P = 0.0858; 95% CI -0.005, 0.102). CONCLUSIONS: Pharmacokinetics of cyclophosphamide and 4-hydroxycyclophosphamide in patients with lupus nephritis and small vessel vasculitis are similar. Clinical and pharmacogenetic covariates alter disposition of cyclophosphamide and 4-hydroxycyclophosphamide. Clinical findings of worsened glomerulonephritis lead to increased exposure to cyclophosphamide vs. the active 4-hydroxycyclophosphamide, which could have relevance in terms of clinical efficacy. The CYP2B6*9 and ABCB1 C3435T polymorphisms alter the pharmacokinetics of cyclophosphamide and 4-hydroxycyclophosphamide in glomerulonephritis.

Pharmacokinetics of valerenic acid in rats after intravenous and oral administrations.

Valerenic acid (VA), a sesquiterpenoid, is one of the major secondary bioactive metabolites of VALERIANA OFFICINALIS L. Until now IN VIVO studies on the absorption, bioavailability, disposition, and metabolism of VA are limited. We established and validated an LC-MS/MS assay for the determination of VA in rat plasma and successfully used this method for pharmacokinetic studies in rats after intravenous (i. v.) and oral administrations. The plasma concentration-time data was analyzed by both non-compartmental and compartmental approaches using WinNonlin software. Following i. v. administration, the disposition of VA in rat plasma was biphasic, subdivided into a fast distribution and a slow elimination phase. The half-life of the distribution phase was 6-12 min, and that of the terminal elimination phase 6-46 h, indicating a possible large tissue binding. Disposition PK of valerenic acid after oral treatment was also described by a two-compartment model with a clearance (CL/F) of 2-5 L · h (-1) · kg (-1) and volume of distribution of (V (d)) 17-20 L · kg (-1). The extent of absorption (F) after oral administration was estimated to be 33.70 % with a half-life of 2.7-5 h. Dose proportionality was observed in terms of dose and AUCs, suggesting linear pharmacokinetics at the dose levels studied in rats.

The Influence of Cannabidiol on the Pharmacokinetics of Methylphenidate in Healthy Subjects.

Introduction: Cannabidiol (CBD) is a widely utilized nonpsychoactive cannabinoid available as an over-the-counter supplement, a component of medical cannabis, and a prescriptive treatment of childhood epilepsies. In vitro studies suggest CBD may inhibit a number of drug-metabolizing enzymes, including carboxylesterase 1 (CES1). The aim of this study was to evaluate effect of CBD on the disposition of the CES1 substrate methylphenidate (MPH). Methods: In a randomized, placebo-controlled, crossover study, 12 subjects ingested 750 mg of CBD solution, or alternatively, a placebo solution twice daily for a 3-day run-in period followed by an additional CBD dose (or placebo) and a single 10 mg dose of MPH and completed serial blood sampling for pharmacokinetic analysis. MPH and CBD concentrations were measured by liquid chromatography with tandem mass spectrometry. Results: The Cmax (mean ± CV) for the CBD group and placebo group was 13.5 ± 43.7% ng/mL and 12.2 ± 36.4% ng/mL, respectively. AUCinf (ng/mL*h) for the CBD group and placebo group was 70.7 ± 32.5% and 63.6 ± 25.4%, respectively. The CBD AUC0-8h (mean ± CV) was 1,542.2 ± 32% ng/mL*h, and Cmax was 389.2 ± 39% ng/mL. When compared to MPH only, the geometric mean ratio (CBD/control, 90% CI) for AUCinf and Cmax with CBD co-administration was 1.09 (0.89, 1.32) and 1.08 (0.85, 1.37), respectively. Discussion/Conclusion: Although the upper bound of bioequivalence was not met, the mean estimates of AUC and Cmax ratios were generally small and unlikely to be of clinical significance.

A randomized, cross-over trial of metoprolol succinate formulations to evaluate PK and PD end points for therapeutic equivalence.

There are limited comparison data throughout the dosing interval for generic versus brand metoprolol extended-release (ER) tablets. We compared the pharmacokinetics (PKs) and pharmacodynamics of brand name versus two generic formulations (drugs 1 and 2) of metoprolol ER tablets with different time to maximum concentration (Tmax ) in adults with hypertension. Participants were randomized to equal drug doses (50-150 mg/day) administered in one of two sequences (brand-drug1-brand-drug2 or brand-drug2-brand-drug1) and completed 24-h PK, digital heart rate (HR), ambulatory blood pressure (BP), and HR studies after taking each formulation for greater than or equal to 7 days. Metoprolol concentrations were determined by liquid chromatography tandem mass spectrometry, with noncompartmental analysis performed to obtain PK parameters in Phoenix WinNonlin. Heart rate variability (HRV) low-to-high frequency ratio was determined per quartile over the 24-h period. Thirty-six participants completed studies with the brand name and at least one generic product. Among 30 participants on the 50 mg dose, the primary PK end points of area under the concentration-time curve and Cmax were similar between products; Tmax was 6.1 ± 3.6 for the brand versus 3.5 ± 4.9 for drug 1 (p = 0.019) and 9.6 ± 3.2 for drug 2 (p < 0.001). Among all 36 participants, 24-h BPs and HRs were similar between products. Mean 24-h HRV low-to-high ratio was also similar for drug 1 (2.04 ± 1.35), drug 2 (1.86 ± 1.35), and brand (2.04 ± 1.77), but was more sustained over time for the brand versus drug 1 (drug × quartile interaction p = 0.017). Differences in Tmax between metoprolol ER products following repeated doses may have implications for drug effects on autonomic balance over the dosing interval.

Inhibitory effects of commonly used herbal extracts on UDP-glucuronosyltransferase 1A4, 1A6, and 1A9 enzyme activities.

The aim of this study was to investigate the effect of commonly used botanicals on UDP-glucuronosyltransferase (UGT) 1A4, UGT1A6, and UGT1A9 activities in human liver microsomes. The extracts screened were black cohosh, cranberry, echinacea, garlic, ginkgo, ginseng, milk thistle, saw palmetto, and valerian in addition to the green tea catechin epigallocatechin gallate (EGCG). Formation of trifluoperazine glucuronide, serotonin glucuronide, and mycophenolic acid phenolic glucuronide was used as an index reaction for UGT1A4, UGT1A6, and UGT1A9 activities, respectively, in human liver microsomes. Inhibition potency was expressed as the concentration of the inhibitor at 50% activity (IC(50)) and the volume in which the dose could be diluted to generate an IC(50)-equivalent concentration [volume/dose index (VDI)]. Potential inhibitors were EGCG for UGT1A4, milk thistle for both UGT1A6 and UGT1A9, saw palmetto for UGT1A6, and cranberry for UGT1A9. EGCG inhibited UGT1A4 with an IC(50) value of (mean ± S.E.) 33.8 ± 3.1 µg/ml. Milk thistle inhibited both UGT1A6 and UGT1A9 with IC(50) values of 59.5 ± 3.6 and 33.6 ± 3.1 µg/ml, respectively. Saw palmetto and cranberry weakly inhibited UGT1A6 and UGT1A9, respectively, with IC(50) values >100 µg/ml. For each inhibition, VDI was calculated to determine the potential of achieving IC(50)-equivalent concentrations in vivo. VDI values for inhibitors indicate a potential for inhibition of first-pass glucuronidation of UGT1A4, UGT1A6, and UGT1A9 substrates. These results highlight the possibility of herb-drug interactions through modulation of UGT enzyme activities. Further clinical studies are warranted to investigate the in vivo extent of the observed interactions.

Nicotine as a factor in stress responsiveness among detoxified alcoholics.

AIMS: The effect of transdermal nicotine on stress reactivity was investigated in currently smoking, detoxified, substance-dependent individuals (65% alcohol dependent, n = 51; 31 male) following a psychosocial stressor. METHODS: Using a randomized, double-blind, placebo-controlled design, subjects were assigned to receive either active transdermal nicotine (low or high dose) or placebo. Six hours following nicotine administration, subjects performed a laboratory psychosocial stressor consisting of two 4-min public-speaking sessions. RESULTS: Consistent with prior reports, substance-dependent individuals displayed a blunted stress response. However, a review of the cortisol distribution data encouraged additional analyses. Notably, a significant minority of the substance-dependent individuals (33%) demonstrated elevated poststress cortisol levels. This group of responders was more likely to be alcohol dependent and to have received the high dose of nicotine [χ2(2) = 32, P < 0.0001], [χ2(2) = 18.66, P < 0.0001]. Differences in salivary cortisol responses between responders and nonresponders could not be accounted for by the length of sobriety, nicotine withdrawal levels, anxiety or depressive symptomatology at the time of the psychosocial stressor. CONCLUSION: These results suggest that nicotine administration may support a normalization of the salivary cortisol response following psychosocial stress in subgroups of substance-dependent individuals, particularly those who are alcohol dependent. Given the association between blunted cortisol levels and relapse, and the complex actions of nicotine at central and peripheral sites, these findings support the systematic study of factors including nicotine, which may influence stress reactivity and the recovery process in alcohol-dependent individuals.

Effects of herbal supplements on drug glucuronidation. Review of clinical, animal, and in vitro studies.

The use of herbal supplements has increased steadily over the last decade. Recent surveys show that many people who take herbal supplements also take prescription and nonprescription drugs, increasing the risk for potential herb-drug interactions. While cytochrome P450-mediated herb-drug interactions have been extensively characterized, the effects of herbal extracts and constituents on UDP-glucuronosyl transferase (UGT) enzymes have not been adequately studied. Thus, the purpose of this review is to evaluate current evidence on the glucuronidation of phytochemicals and the potential for UGT-mediated herb-drug interactions with the top-selling herbal supplements in the United States and Europe. IN VITRO and animal studies indicate that cranberry, GINKGO BILOBA, grape seed, green tea, hawthorn, milk thistle, noni, soy, St. John's wort, and valerian are rich in phytochemicals that can modulate UGT enzymes. However, the IN VIVO consequences of these interactions are not well understood. Only three clinical studies have investigated the effects of herbal supplements on drugs cleared primarily through UGT enzymes. Evidence on the potential for commonly used herbal supplements to modulate UGT-mediated drug metabolism is summarized. Moreover, the need for further research to determine the clinical consequences of the described interactions is highlighted.

Absolute/relative bioavailability and metabolism of dodeca-2E,4E,8Z,10E/Z-tetraenoic acid isobutylamides (tetraenes) after intravenous and oral single doses to rats.

The present study assessed the absolute and relative bioavailabilities of dodeca-2 E,4 E,8 Z,10 E/ Z-tetraenoic acid isobutylamides (tetraenes), the main bioactive constituents in Echinacea, administered as pure compounds or in the form of an Echinacea purpurea root extract preparation. Tetraenes were administered orally by gavage or intravenously in a dose of 0.75 mg/kg. The extract was administered orally in a dose of 158.6 mg/kg which corresponds to the same amount of tetraenes. Pharmacokinetic parameters of tetraenes were calculated by non-compartmental analysis using WinNonlin® 5.2 software. Mean dodeca-2 E,4 E,8 Z,10 E/ Z-tetraenoic acid isobutylamide dose-normalized plasma area under the concentration-time curve (AUC0-∞/dose) was 3.24 ± 0.32 min · ng/mL/µg and 0.95 ± 0.16 min · ng/mL/µg after iv and oral administrations, respectively, and 1.53 ± 0.18 min · ng/mL/µg after oral administration of the Echinacea root extract. The absolute oral bioavailability of dodeca-2 E,4 E,8 Z,10 E/ Z-tetraenoic acid isobutylamides was 29.2 ± 2.3 %, which was increased to 47.1 ± 7.2 % (1.6-fold) by administration of the Echinacea extract. Administration of an Echinacea extract increased blood exposure with no impact on C(max), but prolonged the elimination half-life to 123.3 ± 15.7 min in comparison to 35.8 ± 6.5 min after administration of the pure dodeca-2 E,4 E,8 Z,10 E/ Z-tetraenoic acid isobutylamides.

Inhibition of intestinal and hepatic glucuronidation of mycophenolic acid by Ginkgo biloba extract and flavonoids.

Herb-drug interactions have received more attention in recent years because of the widespread popularity of herbal supplements. However, there are limited data on the effect of herbs on glucuronidation in humans. The goal of this work was to examine the effect of Ginkgo biloba extract and its main flavonoid and terpene lactone constituents on mycophenolic acid (MPA) 7-O-glucuronidation. Human liver (HLM) and intestinal (HIM) microsomes were incubated with MPA and G. biloba extract (unhydrolyzed or acid-hydrolyzed), quercetin, kaempferol, ginkgolide A, ginkgolide B, or bilobalide. MPA-7-O-glucuronide formation was inhibited in HLM and HIM incubations by unhydrolyzed [IC(50) = 84.3 (HLM) and 6.9 (HIM) microg/ml] and hydrolyzed [IC(50) = 20.9 (HLM) and 4.3 (HIM) microg/ml] G. biloba extracts, quercetin [IC(50) = 19.1 (HLM) and 5.8 (HIM) microM], and kaempferol [IC(50) = 23.1 (HLM) and 7.7 (HIM) microM]. Terpene lactones did not show inhibition of MPA glucuronidation. Quercetin was a mixed-type inhibitor in HLM and HIM incubations [K(i) = 11.3 (HLM) and 2.8 (HLM) microM], whereas kaempferol was a noncompetitive inhibitor in HLM (K(i) = 33.7 microM) and a mixed-type inhibitor in HIM (K(i) = 4.5 microM). These results indicate that G. biloba extract or quercetin- and kaempferol-rich supplements may inhibit intestinal and hepatic glucuronidation of MPA. Future studies are needed to evaluate the clinical significance of this interaction.

Inhibitory effects of commonly used herbal extracts on UGT1A1 enzyme activity.

Commonly used herbal supplements were screened for their potential to inhibit UGT1A1 activity using human liver microsomes. Extracts screened included ginseng, echinacea, black cohosh, milk thistle, garlic, valerian, saw palmetto, and green tea epigallocatechin gallate (EGCG). Estradiol-3-O-glucuronide (E-3-G) formation was used as the index of UGT1A1 activity. All herbal extracts except garlic showed inhibition of UGT1A1 activity at one or more of the three concentrations tested. A volume per dose index (VDI) was calculated to estimate the volume in which the daily dose should be diluted to obtain an IC(50)-equivalent concentration. EGCG, echinacea, saw palmetto, and milk thistle had VDI values >2.0 L per dose unit, suggesting a higher potential for interaction. Inhibition curves were constructed for EGCG, echinacea, saw palmetto, and milk thistle. IC(50) values were (mean ± SE) 7.8 ± 0.9, 211.7 ± 43.5, 55.2 ± 9.2, and 30.4 ± 6.9 µg/ml for EGCG, echinacea, saw palmetto, and milk thistle extracts, respectively. Based on our findings, inhibition of UGT1A1 by milk thistle and EGCG and to a lesser extent by echinacea and saw palmetto is plausible, particularly in the intestine where higher extract concentrations are anticipated. Further clinical studies are warranted.

ESRD impairs nonrenal clearance of fexofenadine but not midazolam.

ESRD can affect the pharmacokinetic disposition of drugs subject to nonrenal clearance. Cytochrome P450 (CYP) enzymes, including CYP3A, and multiple intestinal and hepatic drug transporters are thought to mediate this process, but the extent to which kidney disease alters the function of these proteins in humans is unknown. We used midazolam and fexofenadine to assess CYP3A (intestinal and hepatic) and drug transport, respectively, in patients with ESRD and healthy control subjects. We evaluated the effect of uremia on CYP3A and transporter expression in vitro by incubating normal rat hepatocytes and enterocytes with serum drawn from study participants. ESRD dramatically reduced nonrenal transporter function, evidenced by a 63% decrease in clearance (P < 0.001) and a 2.8-fold increase in area under the plasma concentration-time curve for fexofenadine (P = 0.002), compared with control subjects. We did not observe significant differences in midazolam or 1'-hydroxymidazolam clearance or area under the curve after oral administration, suggesting that CYP3A function is not changed by ESRD. Changes in hepatocyte and enterocyte protein expression in the presence of uremic serum were consistent with in vivo results. These findings demonstrate a mechanism for altered drug disposition in kidney disease, which may partially account for the high rates of drug toxicity in this population.

Intensive Care Unit Delirium in Surgical Patients Is Associated with Upregulation in Tryptophan Metabolism.

INTRODUCTION: In intensive care unit (ICU) patients, delirium is frequent, occurs early in ICU admission, and is associated with poor outcomes. Risk models based on clinical factors have shown variable performance in terms of predictive ability. Identification of a candidate biomarker that associates with delirium may lead to a better understanding of disease mechanism, validation biomarker studies, and the ability to develop targeted interventions for prevention and treatment of delirium. This study analyzed metabolite concentrations early in the course of ICU admission to assess the association with delirium onset. METHODS: Within 24 hours of ICU admission, blood samples for global and targeted metabolomics analyses in adult surgical ICU patients were collected prospectively. Metabolites were determined using mass spectrometry/ultra-high-pressure liquid chromatography and analyzed in patients with delirium and a group of controls matched on age, sex, and admission Sequential Organ Function Assessment (SOFA) score. RESULTS: Patients in the study (65 per group) were a mean age of 59 years, had a median SOFA score of 6, and were most commonly admitted to the ICU following major trauma. In the delirium group, median onset of delirium was 3 (interquartile range 1-6) days, and the most common delirium subtype was mixed (56%). Kynurenic acid was significantly increased, and tryptophan concentration was significantly decreased in the delirium group (p=0.04). The ratio of kynurenine-to-tryptophan concentration was significantly higher in the delirium group (p=0.005). CONCLUSIONS: Evidence of upregulation was found in the tryptophan metabolic pathway in delirious patients because tryptophan concentrations were lower, tryptophan metabolites were higher, and the kynurenine-to-tryptophan ratio was increased. These findings suggest a role of increased inflammation and accumulation of neurotoxic metabolites in the pathogenesis of ICU delirium. Future studies should target this pathway to validate metabolites in the tryptophan pathway as risk biomarkers in patients with ICU delirium.

Examination of Metoprolol Pharmacokinetics and Pharmacodynamics Across CYP2D6 Genotype-Derived Activity Scores.

Recent CYP2D6 phenotype standardization efforts by CYP2D6 activity score (AS) are based on limited pharmacokinetic (PK) and pharmacodynamic (PD) data. Using data from two independent clinical trials of metoprolol, we compared metoprolol PK and PD across CYP2D6 AS with the goal of determining whether the PK and PD data support the new phenotype classification. S-metoprolol apparent oral clearance (CLo), adjusted for clinical factors, was correlated with CYP2D6 AS (P < 0.001). The natural log of CLo was lower with an AS of 1 (7.6 ± 0.4 mL/minute) vs. 2-2.25 (8.3 ± 0.6 mL/minute; P = 0.012), similar between an AS of 1 and 1.25-1.5 (7.8 ± 0.5 mL/minute; P = 0.702), and lower with an AS of 1.25-1.5 vs. 2-2.25 (P = 0.03). There was also a greater reduction in heart rate with metoprolol among study participants with AS of 1 (-10.8 ± 5.5) vs. 2-2.25 (-7.1 ± 5.6; P < 0.001) and no significant difference between those with an AS of 1 and 1.25-1.5 (-9.2 ± 4.7; P = 0.095). These data highlight linear trends among CYP2D6 AS and metoprolol PK and PD, but inconsistencies with the phenotypes assigned by AS based on the current standards. Overall, this case study with metoprolol suggests that utilizing CYP2D6 AS, instead of collapsing AS into phenotype categories, may be the most precise approach for utilizing CYP2D6 pharmacogenomics in clinical practice.