WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT• UDP-glucuronosyltransferase (UGT) 2B15 is a major drug glucuronidation enzyme expressed in human liver.• Oxazepam is an isoform-selective probe drug that is being used for in vitro studies of UGT2B15.• The most common UGT2B15 missense polymorphisms (D85Y and K523T) are correlated with variable oxazepam glucuronidation in human liver bank samples.• UGT2B17 is also expressed in liver and has high sequence homology and substrate specificity overlap with UGT2B15. WHAT THIS STUDY ADDS• UGT2B15 D85Y polymorphism is identified as a major determinant of oxazepam disposition, accounting for as much as 34% of interindividual variability in oxazepam apparent oral clearance.• An effect of the UGT2B15 K523T or the UGT2B17 deletion polymorphisms on oxazepam disposition could not be detected.• Provides evidence supporting the use of oxazepam as an isoform-selective in vivo probe for studies of variability in UGT2B15 activity. AIMSAlthough in vitro studies indicate that oxazepam is an isoform-selective substrate probe for UDP-glucuronosyltransferase 2B15, the utility of this drug as an in vivo probe is uncertain. The main aim of this study was to determine whether common missense polymorphisms in the UGT2B15 gene (D85Y and K523T) are associated with altered oxazepam pharmacokinetics and pharmacodynamics. We also determined the possible influence of a common deletion polymorphism in the gene encoding UGT2B17, which shows substantial substrate specificity overlap with UGT2B15. METHODSThirty healthy male subjects were administered 15 mg of oxazepam by mouth followed by plasma oxazepam concentration monitoring for 36 h, and pharmacodynamic testing for 8 h. Genotypes were determined by genomic polymerase chain reaction and commercial 5′-nuclease assays. RESULTSAllele frequencies for D85Y, K523T, UGT2B17del were 47%, 23% and 19%, respectively. Median oxazepam apparent oral clearance was significantly lower in 85YY subjects (1.62 ml min -1 kg -1) compared with 85DD subjects (3.35 ml min -1 kg -1; P = 0.003, Student-Newman-Keuls test), whereas 85DY subjects were intermediate (2.34 ml min -1 kg -1; P = 0.018 vs. 85DD, P = 0.034 vs. 85YY). Regression analysis indicated that UGT2B15 D85Y genotype accounted for 34% of interindividual variability. However, neither UGT2B15 K523T nor UGT2B17del was associated with altered oxazepam disposition. Furthermore, no differences in pharmacodynamic measures, including quantitative electroencephalography, digit-symbol substitution test, self-or observer-rated visual analogue scales, could be demonstrated for any of the polymorphisms evaluated. CONCLUSIONSThese results identify UGT2B15 D85Y as a major determinant of oxazepam clearance, and indicate that oxazepam may be useful as an in vivo probe for glucuronidation by UGT2B15.

Over 30 years ago, black Africans from Kenya and Ghana were shown to metabolize acetaminophen faster by glucuronidation and slower by oxidation compared with white Scottish Europeans. The objectives of this study were to determine whether similar differences exist between African-Americans and European-Americans, and to identify genetic polymorphisms that could explain these potential differences. Acetaminophen plasma pharmacokinetics and partial urinary metabolite clearances via glucuronidation, sulfation, and oxidation were determined in healthy African-Americans (18 men, 23 women) and European-Americans (34 men, 20 women) following a 1-g oral dose. There were no differences in acetaminophen total plasma, glucuronidation, or sulfation clearance values between African-Americans and European-Americans. However, median oxidation clearance was 37% lower in African-Americans versus European-Americans (0.57 versus 0.90 ml/min per kilogram; = 0.0001). Although acetaminophen total or metabolite clearance values were not different between genders, shorter plasma half-life values (by 11-14%; < 0.01) were observed for acetaminophen, acetaminophen glucuronide, and acetaminophen sulfate in women versus men. The UGT2B15*2 polymorphism was associated with variant-allele-number proportional reductions in acetaminophen total clearance (by 15-27%; < 0.001) and glucuronidation partial clearance (by 23-48%; < 0.001). UGT2B15 *2/*2 genotype subjects also showed higher acetaminophen protein-adduct concentrations than *1/*2 (by 42%; = 0.003) and *1/*1 (by 41%; = 0.003) individuals. Finally, CYP2E1 *1D/*1D genotype African-Americans had lower oxidation clearance than *1C/*1D (by 42%; = 0.041) and *1C/*1C (by 44%; = 0.048) African-Americans. Consequently, African-Americans oxidize acetaminophen more slowly than European-Americans, which may be partially explained by the CYP2E1*1D polymorphism. UGT2B15*2 influences acetaminophen pharmacokinetics in both African-Americans and European-Americans.

AIMSTurmeric extract derived curcuminoids (curcumin, demethoxycurcumin and bisdemethoxycurcumin) are currently being evaluated for the treatment of cancer and Alzheimer's dementia. Previous in vitro studies indicate that curcuminoids and piperine (a black pepper derivative that enhances curcuminoid bioavailability) could inhibit human CYP3A, CYP2C9, UGT and SULT dependent drug metabolism. The aim of this study was to determine whether a commercially available curcuminoid/piperine extract alters the pharmacokinetic disposition of probe drugs for these enzymes in human volunteers. METHODSA randomized placebo-controlled six way crossover study was conducted in eight healthy volunteers. A standardized curcuminoid/piperine preparation (4 g curcuminoids plus 24 mg piperine) or matched placebo was given orally four times over 2 days before oral administration of midazolam (CYP3A probe), flurbiprofen (CYP2C9 probe) or paracetamol (acetaminophen) (dual UGT and SULT probe). Plasma and urine concentrations of drugs, metabolites and herbals were measured by HPLC. Subject sedation and electroencephalograph effects were also measured following midazolam dosing. RESULTSCompared with placebo, the curcuminoid/piperine treatment produced no meaningful changes in plasma Cmax, AUC, clearance, elimination half-life or metabolite levels of midazolam, flurbiprofen or paracetamol (a = 0.05, paired t-tests). There was also no effect of curcuminoid/piperine treatment on the pharmacodynamics of midazolam. Although curcuminoid and piperine concentrations were readily measured in plasma following glucuronidase/sulfatase treatment, unconjugated concentrations were consistently below the assay thresholds (0.05-0.08 mM and 0.6 mM, respectively). CONCLUSIONThe results indicate that short term use of this piperine-enhanced curcuminoid preparation is unlikely to result in a clinically significant interaction involving CYP3A, CYP2C9 or the paracetamol conjugation enzymes. WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT• Curcumin and other curcuminoids derived as extracts of turmeric (Curcumina longa) are being developed as potential treatments for cancer and Alzheimer's dementia.• The curcuminoids demonstrate low oral bioavailability in part because of extensive metabolism.• Curcuminoid oral bioavailability can be enhanced by combining with piperine, a black pepper extract.• In vitro studies indicate that both the curcuminoids and piperine could interfere with the metabolism of drugs by CYP3A, CYP2C9, UGT and/or SULT in vivo. WHAT THIS STUDY ADDS• The results of this study indicate that short term use of a piperine-enhanced curcuminoid preparation is unlikely to result in a clinically significant interaction involving drugs metabolized by CYP3A, CYP2C9 or the paracetamol (acetaminophen) conjugation enzymes.• The lack of interaction might be related to the short duration of therapy (2 days) and/or the low (unconjugated) curcuminoid and piperine plasma concentrations that were observed in the subjects despite the use of a standardized piperine-enhanced cur...

AIMThe present study evaluated the possibility of drug interactions involving blueberry juice (BBJ) and substrate drugs whose clearance is dependent on cytochromes P4503A (CYP3A) and P4502C9 (CYP2C9). METHODSA 50:50 mixture of lowbush and highbush BBJ was evaluated in vitro as an inhibitor of CYP3A activity (hydroxylation of triazolam and dealkylation of buspirone) and of CYP2C9 activity (flurbiprofen hydroxylation) using human liver microsomes. In clinical studies, clearance of oral buspirone and oral flurbiprofen was studied in healthy volunteers with and without co-treatment with BBJ. RESULTSBBJ inhibited CYP3A and CYP2C9 activity in vitro, with 50% inhibitory concentrations (IC50) of less than 2%, but without evidence of mechanism-based (irreversible) inhibition. Grapefruit juice (GFJ) also inhibited CYP3A activity, but inhibitory potency was increased by pre-incubation, consistent with mechanism-based inhibition. In clinical studies, GFJ significantly increased area under the plasma concentration-time curve (AUC) for the CYP3A substrate buspirone. The geometric mean ratio (GMR = AUC with GFJ divided by AUC with water) was 2.12. In contrast, the effect of BBJ (GMR = 1.39) was not significant. In the study of flurbiprofen (CYP2C9 substrate), the positive control inhibitor fluconazole significantly increased flurbiprofen AUC (GMR = 1.71), but BBJ had no significant effect (GMR = 1.03). CONCLUSIONThe increased buspirone AUC associated with BBJ is quantitatively small and could have occurred by chance. BBJ has no effect on flurbiprofen AUC. The studies provide no evidence for concern about clinically important pharmacokinetic drug interactions of BBJ with substrate drugs metabolized by CYP3A or CYP2C9.

Nutrient interactions with prescription drugs is a topic of ongoing basic and clinical research. Pomegranate (POM) juice, and a 1-gram capsule containing POM extract, were evaluated in vitro and in vivo as inhibitors of CYP2C9, with flurbiprofen serving as the index substrate. Fluconazole was the positive control inhibitor. The in vitro 50% inhibitory concentrations (IC50) for POM juice and extract were below 1% (v/v), with no evidence of mechanism-based (irreversible) inhibition. In clinical studies, flurbiprofen pharmacokinetics were unchanged by POM juice or extract compared to a low-polyphenol placebo control beverage. However, fluconazole significantly reduced the oral clearance of flurbiprofen. Despite inhibition of CYP2C9 in vitro, POM juice and extract had no effect on CYP2C9 activity in human subjects, and can be consumed by patients taking CYP2C9 substrate drugs with negligible risk of a pharmacokinetic interaction.

Sjögren's syndrome is an autoimmune disorder primarily affecting women, with decreased saliva and tear production as the principal characteristic. Cognitive, neurological, and psychiatric disorders also are associated with Sjögren's. The present study addressed the hypothesis that patients with Sjögren's syndrome differ significantly from matched controls in the prevalence and impact of a number of neuropsychiatric abnormalities. Sjögren's patients and controls (n = 37 per group) underwent medical and psychiatric evaluation, demographic assessments, quality of life and symptom evaluation, and extensive testing of cognitive function and memory. Patients and controls were closely matched for age, gender distribution, verbal IQ, marital status, educational level, employment status, and current/past medical or psychiatric history. On most subjective self-ratings, Sjögren's patients reported greater fatigue, impaired physical functioning, feeling depressed, and autonomic symptomatology compared to controls. Impaired memory was described mainly as loss of thought continuity in the midst of a task or activity. However, the majority of objective measures of cognition, psychomotor function, and memory showed minimal differences between groups. Sjögren's patients rate themselves as impaired on multiple ratings of emotional, cognitive, and physical function, but objective measures of cognition reveal fewer substantive differences between patients and matched controls. Sjögren's patients perceive deteriorated physical function over time, but they achieve a level of functioning comparable to controls despite the burden of their illness.

No abstract

Oxazepam is specifically glucuronidated by UGT2B15. In previous studies we have shown that a common non‐synonymous polymorphism in the UGT2B15 gene (*2, D85Y) results in lower oxazepam glucuronidation by recombinant enzyme and human liver microsomes. The goal of this study was to determine the effect of UGT2B15*2 on the pharmacokinetics of oxazepam in 30 healthy male subjects administered 15 mg oxazepam by mouth. UGT2B15 genotype frequencies were 0.20, 0.67 and 0.13 for *1/*1, *1/*2 and *2/*2, respectively. Mean (+/‐ SD) plasma oxazepam area under the curve values extrapolated to infinity were significantly higher (P<0.001, ANOVA) in *2/*2 subjects (2.50 +/‐ 0.96 ug/mL*hr) compared with *1/*2 (1.37 +/‐ 0.40) and *1/*1 (0.981 +/‐ 0.29) subjects. Furthermore, mean weight‐normalized plasma clearance values were significantly lower (P=0.003, ANOVA) in *2/*2 subjects (1.55 +/‐ 0.61 mL/min/kg) compared with *1/*2 (2.56 +/‐ 0.74) and *1/*1 (3.53 +/‐ 1.14) subjects. These results mirror our previous in vitro results and substantiate the UGT2B15*2 polymorphism as a major determinant of oxazepam clearance in vivo. (Supported by NIH grants GM‐61834, DK‐79300, AI‐058784, and AG‐017880.)