Simultaneous Determination of Decursin, Decursinol Angelate, Nodakenin, and Decursinol of Angelica gigas Nakai in Human Plasma by UHPLC-MS/MS: Application to Pharmacokinetic Study

Coumarins in Cham-dang-gwi, the dried root of Angelica gigas Nakai (AGN), possess pharmacological effects on anemia, pain, infection, and articular rheumatism. The AGN root containes decursin (D), decursinol angelate (DA), nodakenin, and decursinol (DOH), a major metabolite of D and DA. The aim of this study was to develop a simultaneous determination method for these four coumarins in human plasma using ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Chromatographic separation was performed on dual columns (Kinetex^® C₁₈ column and Capcell core C₁₈ column) with mobile phase consisting of water and acetonitrile at a flow rate of 0.3 mL/min using gradient elution. Multiple reaction monitoring was operated in positive ion mode with precursors to product ion transition values of m/z 328.9→228.8, 328.9→228.9, 409.4→248.8, and 246.8→212.9 to measure D, DA, nodakenin, and DOH, respectively. Linear calibration curves were fitted over concentration range of 0.05–50 ng/mL for these four components, with correlation coefficient greater than 0.995. Inter- and intra-day accuracies were between 90.60% and 108.24%. These precisions were within 11.19% for all components. The established method was then applied to a pharmacokinetic study for the four coumarins after usual dosing in Korean subjects.

A simple high-performance liquid chromatographic method for the determination of brazilin and its application to a pharmacokinetic study in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Caesalpinia sappan is a medicinal plant native to China popularly used to treat chronic pelvic inflammation, dysmenorrhea and hysteromyoma. Its main bioactive component is brazilin which had presented antibacterial, anti-inflammatory and anti-platelet aggregation activities. To establish a sensitive, selective, reproducible, and accurate high performance liquid chromatographic (HPLC) method for the quantitative determination of brazilin in plasma, and study the pharmacokinetics of brazilin in rats after intravenous administration of brazilin.

MATERIALS AND METHODS

Rats received intravenous injection of 25, 50 and 100mg/kg of brazilin. Concentrations of brazilin in plasma were determined by HPLC method at different time points and all pharmacokinetic parameters were estimated by non-compartmental analysis with WinNonLin 6.2 software.

RESULTS

After single intravenous doses of 25, 50 and 100mg/kg brazilin in rats, the main PK parameters were as follows: Cmax were 18.1 ± 4.1, 46.7 ± 8.7 and 82.2 ± 9.6 µg/mL; AUC0-24 were 20.4 ± 4.3, 48.7 ± 6.8 and 90.4 ± 10.3 µgh/mL; and t1/2 were 5.4 ± 1.5, 5.8 ± 0.9 and 6.2 ± 1.2h, respectively.

CONCLUSION

It showed that the brazilin was eliminated moderately in rat by intravenous injection route with t1/2 of 6h and showed a dose-dependence profile of Cmax and AUC0-24 at the doses of 25~100mg/kg of brazilin for injection in rats.

Biomarkers of human exposure to personal care products: results from the Flemish Environment and Health Study (FLEHS 2007-2011)

Personal care products (PCPs), such as soaps, perfumes, cosmetics, lotions, etc., contain a variety of chemicals that have been described as potentially hormone disrupting chemicals. Therefore, it is important to assess the internal exposure of these chemicals in humans. Within the 2nd Flemish Environment and Health Study (FLEHS II, 2007-2011), the human exposure to three classes of pollutants that are present in a wide variety of PCPs--i.e. polycyclic musks (galaxolide, HHCB and tonalide, AHTN in blood), parabens (urinary para-hydroxybenzoic acid, HBA) and triclosan (urinary TCS)--was assessed in 210 Flemish adolescents (14-15 years) and in 204 adults (20-40 years) randomly selected from the general population according to a stratified two stage clustered study design. The aim of this study was to define average levels of exposure in the general Flemish population and to identify determinants of exposure. Average levels (GM (95% CI)) in the Flemish adolescents were 0.717 (0.682-0.753) μg/L for blood HHCB; 0.118 (0.108-0.128) μg/L for blood AHTN; 1022 (723-1436) μg/L for urinary HBA and 2.19 (1.64-2.92) μg/L for urinary TCS. In the adults, levels of HBA were on average 634 (471-970) μg/L. Inter-individual variability was small for HHCB and AHTN, intermediate for HBA, and large for TCS. All biomarkers were positively associated with the use of PCPs. Additionally, levels of HHCB and AHTN increased with higher educational level of the adolescents. Both in adults and adolescents, urinary HBA levels were negatively correlated with BMI. We define here Flemish exposure values for biomarkers of PCPs, which can serve as baseline exposure levels to identify exposure trends in future biomonitoring campaigns.

Single oral dose pharmacokinetics of decursin, decursinol angelate, and decursinol in rats

Decursin and decursinol angelate are the major components in the alcoholic extract of the root of Angelica gigas Nakai. Our previous work convincingly demonstrated that both decursin and decursinol angelate were rapidly converted to decursinol in mice after administration by either oral gavage or i. p. injection. In the current study, we compared for the first time the plasma profiles of decursinol, when equal moles of decursin/decursinol angelate or decursinol were given to rats by oral gavage, and investigated the effect of different formulas and other chemicals in Angelica gigas extract on the bioavailability of decursinol. Our results show that gavage of decursinol led to a faster attainment of plasma decursinol peak (Tmax ~ 0.7 h) and much higher peak levels than an equal molar amount administered as decursin/decursinol angelate mixture or as Angelica gigas ethanol extract, resulting in 2-3 fold higher bioavailability as estimated by the area under the curve of the respective regimens (65 012 vs. 27 033 h · ng/mL for decursinol and decursin/decursinol angelate treatment groups, respectively). Compared to a formula based on ethanol-PEG400-Tween80, carboxyl methyl cellulose was a less optimized vehicle. In addition, we detected peak levels of decursin and decursinol angelate in the plasma of rats administered with decursin/decursinol angelate or Angelica gigas extract in the nM range (Tmax ~ 0.5 h) with a newly established sensitive UHPLC-MS/MS method. Furthermore, our data support the liver, instead of intestine, as a major organ site where decursin and decursinol angelate were hydrolyzed to decursinol with a S9 microsomal in vitro metabolism assay. Taken together, our study provided important PK, LC-MS/MS methodology, formulation and metabolism insights in a rodent model for the rational design of in vivo efficacy studies of the corresponding chemicals in the future.

KCN1, a novel synthetic sulfonamide anticancer agent: in vitro and in vivo anti-pancreatic cancer activities and preclinical pharmacology

The purpose of the present study was to determine the in vitro and in vivo anti-cancer activity and pharmacological properties of 3,4-dimethoxy-N-[(2,2-dimethyl-2H-chromen-6-yl)methyl]-N-phenylbenzenesulfonamide, KCN1. In the present study, we investigated the in vitro activity of KCN1 on cell proliferation and cell cycle distribution of pancreatic cancer cells, using the MTT and BrdUrd assays, and flow cytometry. The in vivo anti-cancer effects of KCN1 were evaluated in two distinct xenograft models of pancreatic cancer. We also developed an HPLC method for the quantitation of the compound, and examined its stability in mouse plasma, plasma protein binding, and degradation by mouse S9 microsomal enzymes. Furthermore, we examined the pharmacokinetics of KCN1 following intravenous or intraperitoneal injection in mice. Results showed that, in a dose-dependent manner, KCN1 inhibited cell growth and induced cell cycle arrest in human pancreatic cancer cells in vitro, and showed in vivo anticancer efficacy in mice bearing Panc-1 or Mia Paca-2 tumor xenografts. The HPLC method provided linear detection of KCN1 in all of the matrices in the range from 0.1 to 100 µM, and had a lower limit of detection of 0.085 µM in mouse plasma. KCN1 was very stable in mouse plasma, extensively plasma bound, and metabolized by S9 microsomal enzymes. The pharmacokinetic studies indicated that KCN1 could be detected in all of the tissues examined, most for at least 24 h. In conclusion, our preclinical data indicate that KCN1 is a potential therapeutic agent for pancreatic cancer, providing a basis for its future development.

Transepithelial transport of theasinensins through Caco-2 cell monolayers and their absorption in Sprague-Dawley rats after oral administration

The aim of this study is to illustrate the in vivo and in vitro absorption of theasinensins B and A that are (-)-epigallocatechin-3-O-gallate (EGCG)-(-)-epigallocatechin (EGC) dimer and EGCG dimer, respectively, and their transport pathway across the intestinal membrane. Our animal study by a single oral administration to rats demonstrated the intact absorption of theasinensins into the blood system, which was estimated to be a >10-fold lower absorption amount than EGCG. The in vitro absorption study indicated that theasinensins can be transported across Caco-2 cell monolayers, while their permeability coefficients were also >10-fold lower than those of EGCG and EGC. Transport experiments using cytochalasin D or quercetin as a tight junction (TJ) modulator and a non-saturable permeation revealed that theasinensins were transported across Caco-2 cells in a TJ paracellular diffusion route. In conclusion, the dimers of condensed catechins, theasinensins B and A, can be absorbed intact into rat blood and transported across Caco-2 cell monolayers probably through a TJ paracellular pathway.

First-pass metabolism of decursin, a bioactive compound of Angelica gigas, in rats

Decursin is considered the major bioactive compound of Angelica gigas roots, a popular Oriental herb and dietary supplement. In this study, the pharmacokinetics of decursin and its active metabolite, decursinol, were evaluated after the administration of decursin in rats. The plasma concentration of decursin decreased rapidly, with an initial half-life of 0.05 h. It was not detectable at 1 h after intravenous administration at an area under the plasma concentration-time curve of 1.20 µg · mL-1·h, whereas the concentration of decursinol increased rapidly reaching a maximum concentration of 2.48 µg · mL-1 at the time to maximum plasma concentration of 0.25 h and an area under the plasma concentration-time curve of 5.23 µg · mL-1·h. Interestingly, after oral administration of decursin, only decursinol was present in plasma, suggesting an extensive hepatic first-pass metabolism of decursin. The extremely low bioavailability of decursin after its administration via the hepatic portal vein (the fraction of dose escaping first-pass elimination in the liver, FH = 0.11) is indicative of extensive hepatic first-pass metabolism of decursin, which was confirmed by a tissue distribution study. These findings suggest that decursin is not directly associated with the bioactivity of A. gigas and that it may work as a type of natural prodrug of decursinol.

Quantitative determination of decursin, decursinol angelate, and decursinol in mouse plasma and tumor tissue using liquid-liquid extraction and HPLC

The pyranocoumarin compound decursin and its isomer decursinol angelate (DA) are the major hydrophobic phytochemicals in the root of Angelica gigas Nakai (AGN, Korean Angelica), a major traditional medicinal herb. The ethanol extract of AGN and especially the purified decursin and DA have been shown to exhibit antitumor activities by our collaborative team and others. Although decursinol has been identified as a major hydrolysis metabolite of decursin and DA in vivo in previous pharmacokinetic studies with mouse and rat, other recently published results sharply disputed this conclusion. In this study, we set up a practical method for the concurrent analysis of decursin, DA, and decursinol in mouse plasma and tumor tissues by liquid-liquid extraction and HPLC-UV and applied the method to several animal experiments. Plasma or tumor homogenate was extracted directly with ethyl acetate. The extraction efficiency for decursin/DA (quantitated together) and decursinol was between 82-95 % in both mouse plasma and tumor homogenate. The lower limit of quantitation (LLOQ) was approximately 0.25 µg/mL for decursin/DA and 0.2 µg/mL for decursinol in mouse plasma. In a pilot pharmacokinetic study, male C57BL/6 mice were given a single dose of 4.8 mg decursin/DA mixture (~240 mg/kg) per mouse either by oral gavage or intraperitoneal injection. Maximum plasma concentrations for decursin/DA and decursinol were 11.2 and 79.7 µg/mL, respectively, when decursin/DA was administered via intraperitoneal injection, and 0.54 and 14.9 µg/mL via oral gavage. Decursin/DA and decursinol contents in the tumor tissues from nude mouse xenografts correlated very well with those in plasma. Overall, our results confirm the conclusion that the majority of decursin/DA hydrolyze to decursinol in rodent models with a tiny fraction remaining as the intact compounds administered.

Effect of food on the pharmacokinetic profile of etamicastat (BIA 5-453)

BACKGROUND

Etamicastat is a novel, potent, and reversible peripheral dopamine-β-hydroxylase inhibitor that has been administered orally at doses up to 600 mg once daily for 10 days to male healthy volunteers and appears to be well tolerated.

OBJECTIVE

The aim of this study was to investigate the effect of food on the pharmacokinetics of etamicastat.

MATERIAL AND METHODS

A single-center, open-label, randomized, two-way crossover study in 12 healthy male subjects was performed. Subjects were administered a single dose of etamicastat 200 mg following either a standard high-fat and high-calorie content meal (test) or 10 hours of fasting (reference). The statistical method for testing the effect of food on the pharmacokinetic parameters of interest was based upon the 90% confidence interval (CI) for the test/reference geometric mean ratio (GMR). The parameters of interest were maximum plasma concentration (C(max)), area under the plasma concentration-time curve (AUC) from time zero to the last measurable concentration (AUC(last)), and AUC from time zero to infinity (AUC(∞)). Bioequivalence was assumed when the 90% CI fell within the recommended acceptance interval (80, 125).

RESULTS

Etamicastat C(max), AUC(last), and AUC(∞) were 229 ng/mL, 1856 ng · h/mL, and 2238 ng · h/mL, respectively, following etamicastat in the fasting, and 166 ng/mL, 1737 ng · h/mL, and 2119 ng · h/mL, respectively, following etamicastat in the fed condition. Etamicastat test/reference GMR was 72.27% (90% CI 64.98, 80.38) for C(max), 93.59% (90% CI 89.28, 98.11) for AUC(last), and 96.47% (90% CI 91.67, 101.53) for AUC(∞). Time to C(max) was prolonged by the presence of food (p < 0.001). The C(max), AUC(last), and AUC(∞) values of the inactive metabolite BIA 5-961 were 275 ng/mL, 1827 ng · h/mL, and 2009 ng · h/mL, respectively, in the fasting, and 172 ng/mL, 1450 ng · h/mL, and 1677 ng · h/mL, respectively, in the fed condition. BIA 5-961 test/reference GMR was 62.42% (90% CI 56.77, 68.63) for C(max), 79.41% (90% CI 56.77, 68.63) for AUC(last), and 83.47% (90% CI 76.62, 90.93) for AUC(∞). A total of six mild to moderate unspecific adverse events were reported by four subjects. There was no clinically significant abnormality in laboratory assessments.

CONCLUSION

Etamicastat was well tolerated. The C(max) of etamicastat decreased 28% following oral administration of etamicastat in the presence of food, while AUC remained within the pre-defined acceptance interval. The delay in absorption and decrease in peak exposure of etamicastat is not clinically significant, and therefore etamicastat could be administered without regard to meals.

TRIAL REGISTRATION

EudraCT No. 2007-006530-33.

Occurrence of synthetic musk fragrances in human blood from 11 cities in China

We measured two nitro musk fragrances (musk xylene) and musk ketone) and five polycyclic musk fragrances (galaxolide [HHCB], tonalide [AHTN], celestolide [ADBI], traseolide [ATII], and phantolide [AHMI]) in human blood samples from 11 cities of China (n = 204). Possible temporal trends in musk concentrations and associations with personal factors, such as gender, age, and others, were studied. Galaxolide (HHCB) showed the highest median concentration (0.85 ng/g) followed by AHTN (0.53 ng/g) with high detection frequency (91 and 77%, respectively). Concentrations of the other synthetic musk fragrances, including musk ketone and musk xylene, were all below the quantification limits. The results suggested that musk concentrations were not significantly relative to gender and body weight but positively correlated with age groups and locations. Apparent differences were also observed in the ratios of HHCB to AHTN concentrations among different cities.

Simultaneous determination of fixed dose combination of nebivolol and valsartan in human plasma by liquid chromatographic-tandem mass spectrometry and its application to pharmacokinetic study

A rapid, sensitive and accurate liquid chromatographic-tandem mass spectrometry method is described for the simultaneous determination of nebivolol and valsartan in human plasma. Nebivolol and valsartan were extracted from plasma using acetonitrile and separated on a C18 column. The mobile phase consisting of a mixture of acetonitrile and 0.05 mM formic acid (50:50 v/v, pH 3.5) was delivered at a flow rate of 0.25 ml/min. Atmospheric pressure ionization (API) source was operated in both positive and negative ion mode for nebivolol and valsartan, respectively. Selected reaction monitoring mode (SRM) using the transitions of m/z 406.1-->m/z 150.9; m/z 434.2-->m/z 179.0 and m/z 409.4-->m/z 228.1 were used to quantify nebivolol, valsartan and internal standard (IS), respectively. The linearity was obtained over the concentration range of 0.01-50.0 ng/ml and 1.0-2000.0 ng/ml and the lower limits of quantitation were 0.01 ng/ml and 1.0 ng/ml for nebivolol and valsartan, respectively. This method was successfully applied to the pharmacokinetic study of fixed dose combination (FDC) of nebivolol and valsartan formulation product after an oral administration to healthy human subjects.

Determination of bergenin in rat plasma by high-performance liquid chromatography

A simple, sensitive, selective and reproducible reversed-phase high-performance liquid chromatography (HPLC) method was developed for the determination of bergenin in rat plasma after intravenous administration. Acetaminophen was successfully used, as internal standard (IS) for calibration. The chromatographic separation was accomplished on a reversed-phase C18 column using a mobile phase consisting of methanol-water (20:80, v/v, pH 2.50) and a detection wavelength of 275 nm. Retention times of bergenin and acetaminophen were approximately 9.9 and 6.1 min and no interfering peak of the blank plasma chromatograms was observed. Good linearity was achieved in the range of 0.3 - 100 microg/ml (r2 = 0.9998). The extraction recoveries of bergenin from plasma was 70.82%, 69.44%, 70.98% at concentrations of 5, 50, 100 microg/ml. Intra-assay and inter-assay variabilities were 0.92 - 2.60% and 2.31 - 2.95%, respectively. The accuracy was validated by relative error (RE%), which was in the range of -0.05 - 1.74%. The capability of the assay to pharmacokinetic studies was demonstrated by the determination of bergenin in plasma after intravenous administration to rats in doses of 7.5 mg/kg, 15.0 mg/kg, and 30.0 mg/kg, using water as the solvent. The half-lives for distribution and elimination are not related to administered doses. A biphasic phenomenon with a rapid distribution followed by a slower elimination phase was observed from the plasma concentration-time curve and the pharmacokinetics was based on first order kinetics.

Quantitation of Armillarisin A in human plasma by liquid chromatography–electrospray tandem mass spectrometry

A rapid and sensitive LC-MS/MS method for quantifying Armillarisin A in human plasma after a single oral dose (40 mg) has been developed and validated. Sample preparation used liquid-liquid extraction with a mixture of diethyl ether-dichloromethane (60:40, v/v) in an acidic environment. The retention times of Armillarisin A and the internal standard, probenecid, were 1.63 and 1.78 min, respectively. The calibration curve was linear over the range 0.15-50 ng/mL with a limit of quantitation of 0.15 ng/mL. The coefficient of variation as a measure of intra- and inter-day precision was <9.3% and the accuracy was in the range 92.5-108.0%. The Armillarisin A concentration-time profile in human plasma was determined after an oral dose of a 40 mg tablet.

The influence of CYP2D6 phenotype on the clinical response of nebivolol in patients with essential hypertension

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

* The variability in drug metabolism has been recognized as an important factor in the occurrence of adverse effects or lack of therapeutic efficacy. * The metabolism of the third-generation beta(1)-receptor antagonist nebivolol has been shown to be highly dependent on cytochrome P450 2D6 enzymatic activity in preclinical studies.

WHAT THIS STUDY ADDS

* This paper assesses the role of a cytochrome P450 2D6 gene defect on the antihypertensive response to nebivolol in a clinical setting. * Despite significant differences in drug disposition, the chronic administration of nebivolol produced similar efficacy and tolerability in hypertensive patients either characterized as poor or extensive metabolizers of the drug. * The study offers insight into the relative contribution of nebivolol enantiomers in systemic blood pressure control.

AIMS

Nebivolol is a beta(1)-adrenergic receptor antagonist with vasodilating properties used in the treatment of hypertension. It is administered as a racemic mixture (D- and L-nebivolol) and is highly metabolized by the cytochrome P-450 2D6 (CYP2D6). The purpose of this study was to determine the role of CYP2D6 phenotypes on the efficacy and tolerability of nebivolol during chronic administration to patients with essential hypertension.

METHODS

Two hundred and eighteen patients were genotyped and phenotyped for CYP2D6 activity, allowing to find and match 14 poor metabolizers (PMs) with 23 extensive metabolizers (EMs). Patients took rac-nebivolol 5 mg daily for 12 weeks. Blood pressure (BP), heart rate, adverse events, plasma levels of the two enantiomers D- and L-nebivolol and their corresponding hydroxymetabolites were assessed.

RESULTS

The metabolic disposition of nebivolol was enantioselective and highly influenced by CYP2D6 phenotypes. Mean steady-state plasma concentrations of D- and L-nebivolol were 10- and 15-fold greater in PMs than in EMs, respectively (P < 0.0001). Despite these differences in the pharmacokinetics of nebivolol, EMs and PMs displayed similar BP responses. Mean reductions in sitting systolic and diastolic BPs were -11/-10 +/- 9/4 mmHg in EMs and -11/-9 +/- 10/5 mmHg in PMs. Side-effects were mild to moderate and not different between groups.

CONCLUSION

Polymorphisms in the gene encoding CYP2D6 significantly influenced the metabolism of nebivolol, but not its antihypertensive efficacy and tolerability. The similar clinical response between EMs and PMs could be explained by the contribution of active hydroxylated metabolites of nebivolol to its antihypertensive actions in EMs.

Simultaneous determination of paclitaxel and a new P-glycoprotein inhibitor HM-30181 in rat plasma by liquid chromatography with tandem mass spectrometry

An LC-MS/MS method for the simultaneous determination of a new P-glycoprotein inhibitor 4-oxo-4H-chromene-2-carboxylic acid [2-(2-(4-[2-(6,7-dimethoxy-3,4-dihydro-1H-isoquinolin-2-yl)-ethyl]-phenyl)-2H-tetrazol-5-yl)-4,5-dimethoxy-phenyl]-amide (HM-30181) and a P-glycoprotein substrate paclitaxel in rat plasma was developed to simultaneously evaluate the pharmacokinetics of paclitaxel and HM-30181 in the rats. HM-30181, paclitaxel, HM-30059 (internal standard (I.S.) for HM-30181), and docetaxel (I.S. for paclitaxel) were extracted from rat plasma with methyl-tert-butyl ether and analyzed on an Atlantis C18 column (5 microm, 2.1 x 100 mm) with the mobile phase of ACN/10 mM ammonium formate (75:25 v/v). The analytes were detected using an ESI MS/MS in the multiple reaction monitoring (MRM) mode. The standard curves for HM-30181 and paclitaxel in plasma were linear (r > 0.999) over the concentration range of 2.0-500 ng/mL with a weighting of 1/concentration2. The method showed a satisfactory sensitivity (2 ng/mL using 50 microL plasma), precision (CV: < or = 6.6%), accuracy (relative error: -6.3 to 2.0%), and selectivity. This method was successfully applied to the pharmacokinetic study of HM-30181 and paclitaxel in rat plasma after oral-coadministration of paclitaxel and HM-30181 to male Sprague- Dawley rats.

Column-switching high-performance liquid chromatographic method for the determination of zaltoprofen in rat plasma

A direct injection column-switching high-performance liquid chromatography (HPLC) method was developed and validated for quantification of zaltoprofen in rat plasma. Following dilution with mobile phase A, i.e. acetonitrile-10mM potassium phosphate buffer (pH 6.8) (12:88, v/v) samples were directly injected to the pre-column without sample pre-purification step. After endogenous plasma components were eluted to waste, the system was switched and the analyte was eluted to the trap column. Zaltoprofen was then back-flushed to the analytical column for separation with mobile phase B, i.e. acetonitrile-10mM potassium phosphate buffer (pH 6.8) (35:65, v/v) and quantification with an ultraviolet detector at 230 nm. The calibration curve was linear in the concentration range of 40-5000 ngmL(-1). This method has been fully validated and shown to be specific, accurate and precise. The method is simple, rapid and the sample preparation is minimal and appears to be useful for the pharmacokinetic study of zaltoprofen.

Effects of soybean glyceollins and estradiol in postmenopausal female monkeys

Glyceollins are a novel class of soybean phytoalexins with potential cancer-protective antiestrogenic effects. The purpose of this study was to evaluate the estrogen-antagonist effects of glyceollin-enriched soy protein on biomarkers for breast cancer risk. Thirty female postmenopausal cynomolgus macaques were randomized to one of three dietary treatments for 3 wk: 1) estradiol (E2, 1 mg/day) + casein/lactalbumin (control); 2) E2 + soy protein isolate (SPI) containing 194 mg/day isoflavonoids; and 3) E2 + glyceollin-enriched soy protein (GLY) containing 189 mg/day isoflavonoids + 134 mg/day glyceollins. Doses are expressed in calorically scaled human equivalents. Mean serum glyceollin concentrations at 4 h postfeeding were 134.2 +/- 34.6 nmol/L in the GLY group and negligible in the SPI group (P = 0.0007). Breast proliferation was significantly increased in the control group (+237%, P = 0.01) but not in the SPI group (+198%, P = 0.08) or GLY group (+36%, P = 0.18). Gene expression of trefoil factor 1 and progesterone receptor, two markers of estrogen receptor activity in breast epithelium, were also significantly higher in the control (P < 0.05 for both) but not in the GLY group. These preliminary findings suggest that soybean glyceollins are natural compounds with potential estrogen-modulating properties in the breast.

Determination of zaltoprofen in human plasma by liquid chromatography with electrospray tandem mass spectrometry: Application to a pharmacokinetic study

In the present study, we developed a method coupling liquid-liquid extraction (LLE) to high-performance liquid chromatography (HPLC) with positive ion electrospray ionization tandem mass spectrometry (ESI-MS/MS) to determine zaltoprofen levels in human plasma, using enalapril as internal standard (IS). The high sensitivity and specificity of MS/MS detection enabled the use of small plasma volumes (250 microL) and a simple LLE procedure. Furthermore, the short run-times (2 min) involved are compatible with the requirements of large-scale clinical studies. Ion acquisition was performed in multiple reaction monitoring (MRM) mode by monitoring the transitions m/z 299.3 > 225.0 for zaltoprofen and m/z 377.4 > 234.2 for the IS enalapril. The limit of detection (LOD) was 0.01 microg/mL and the lower limit of quantitation (LLOQ) was 0.05 microg/mL. The devised method was linear over the studied range (0.05-20 microg/mL), with r2 > 0.99 and a run-time of 2 min. Intra-day precisions fell in the range 2.0-13.8%, inter-day precisions in the range 2.1-3.9%, and intra- and inter-day accuracies in the range 102.8-114.1%. The described method provides a fast and sensitive analytical tool for zaltoprofen and was successfully applied to a 24-subject pharmacokinetic study.

Evaluation of Interethnic Differences in Repinotan Pharmacokinetics by Using Population Approach

Repinotan is a selective full serotonin receptor agonist at the 5-HT1A subtype which has been studied in phase I and II studies involving over 500 healthy subjects and patients. Repinotan is primarily metabolized by CYP2D6 which is known to be subject to polymorphism and ethnic differences in its quantitative and qualitative expression pattern. In order to investigate the effect of ethnicity on repinotan pharmacokinetics (PK) between a Caucasian and Japanese population and to explain PK variability, this population PK evaluation was conducted. A population PK model was established based on the data of 1314 blood samples from 241 patients from 3 Phase II studies. This analysis has characterized the repinotan PK, with particular attention to ethnicity. Using the MIXTURE subroutine of NONMEM, evidence was provided for different CL groups. Repinotan plasma levels in the 'High CL' subgroup, which comprised the majority of patients, did not show relevant differences between a Japanese and Caucasian population. In the 'Low CL' subgroup, Japanese and Caucasian populations were different. These findings are consistent with the published literature, which reports ethnic differences in the distribution of CYP2D6 activity. The finding of a greater percentage of patients with intermediate CL in the Japanese population falling between poor and extensive metabolizers is consistent with the distribution pattern of CYP2D6 in the Japanese population. The results of this evaluation can be used to assist in designing future trials.

Determination and pharmacokinetic study of bergenin in rat plasma by RP-HPLC method

A validated reversed-phase high-performance liquid chromatographic (RP-HPLC) method was developed for the determination of bergenin in rat plasma. Bergenin in rat plasma was extracted with methanol, which also acted as a deproteinization agent. Chromatographic separation of bergenin was performed on a C(18) column, with a mobile phase of methanol-water (22:78, v/v) at a flow-rate of 0.8 mL/min and an operating temperature of 40 degrees C, and UV detection was set at 220 nm. The calibration curve was linear over the range 0.25-50 microg/mL (r = 0.9990) in rat plasma. The limit of quantification was 0.25 microg/mL using a plasma sample of 100 microL. The extraction recoveries were 83.40 +/- 6.02, 81.49 +/- 2.40 and 72.51 +/- 2.64% at concentrations of 0.5, 5 and 50 microg/mL, respectively. The intra-day and inter-day precision and accuracy were validated by relative standard deviation (RSD%) and relative error (RE%), which were in the ranges 3.74-9.91 and -1.6-8.0%. After intravenous administration to rats at the dose of 11.25 mg/kg, the plasma concentration-time curve of bergenin was best conformed to a two-compartment open model. The main pharmacokinetic parameters indicated that bergenin exhibited a wide distribution and moderate elimination velocity in rat.

Rapid quantification of nebivolol in human plasma by liquid chromatography coupled with electrospray ionization tandem mass spectrometry

A simple, sensitive and rapid liquid chromatographic/electrospray ionization tandem mass spectrometric method was developed and validated for the quantitation of nebivolol in human plasma. The method involved a simple single-step liquid-liquid extraction with diethyl ether/dichloromethane (70/30). The analyte was chromatographed on Waters symmetry C18 reversed-phase chromatographic column by isocratic elution with water:acetonitrile:formic acid (30:70:0.03, v/v) and analyzed by mass spectrometry in the multiple reaction monitoring mode. The precursor to product ion transitions of m/z 406.4-151.5 and m/z 409.1-228.1 were used to measure the analyte and the internal standard (I.S.), respectively. The chromatographic runtime was 2 min and the weighted (1/x2) calibration curves were linear over the range 50-10,000 pg/mL. The method was validated in terms of accuracy, precision, absolute recovery, freeze-thaw stability, bench-top stability and re-injection reproducibility. The limit of detection and lower limit of quantification in human plasma were 10 and 50 pg/mL, respectively. The within- and between-batch accuracy and precision were found to be well within acceptable limits (<10%). The analyte was stable after three freeze-thaw cycles (deviation <10%). The average absolute recoveries of nebivolol and tamsulosin, used as an internal standard, from spiked plasma samples were 73.4+/-3.7 and 72.1+/-2.0%, respectively. The assay method described here was applied to study the pharmacokinetics of nebivolol.

Comparative evaluation of positron emission tomography radiotracers for imaging the norepinephrine transporter: (S,S) and (R,R) enantiomers of reboxetine analogs ([11C]methylreboxetine, 3-Cl-[11C]methylreboxetine and [18F]fluororeboxetine), (R)-[11C]nisoxetine, [11C]oxaprotiline and [11C]lortalamine

We have synthesized and evaluated several new ligands for imaging the norepinephrine transporter (NET) system in baboons with positron emission tomography (PET). Ligands possessing high brain penetration, high affinity and selectivity, appropriate lipophilicity (log P = 1.0-3.5), high plasma free fraction and reasonable stability in plasma were selected for further studies. Based on our characterization studies in baboons, including 11C-labeled (R)-nisoxetine (Nis), oxaprotiline (Oxap), lortalamine (Lort) and new analogs of methylreboxetine (MRB), in conjunction with our earlier evaluation of 11C and 18F derivatives of reboxetine, MRB and their individual (R,R) and (S,S) enantiomers, we have identified the superiority of (S,S)-[11C]MRB and the suitability of MRB analogs [(S,S)-[11C]MRB > (S,S)-[11C]3-Cl-MRB > (S,S)-[18F]fluororeboxetine] as potential NET ligands for PET. In contrast, Nis, Oxap and Lort displayed high uptake in striatum (higher than in thalamus). The use of these ligands is further limited by high non-specific binding and relatively low specific signal, as is characteristic of many earlier NET ligands. Thus, to our knowledge (S,S)-[11C]MRB remains by far the most promising NET ligand for PET studies.

Blood concentrations of polycyclic musks in healthy young adults

Knowledge on the concentration of polycyclic musk fragrance compounds in human blood is sparse. This study examined the concentrations of six polycyclic musks in blood samples from healthy volunteers. Blood was taken from hundred healthy students of the Medical University of Vienna. The lipophilic fraction was extracted and after purification analyzed by GC-MS. Study participants also completed a questionnaire on the use of cosmetics, about nutrition and other life-style aspects. Two compounds -- galaxolide and tonalide -- were identified in higher percentages of the blood plasma samples. Maximum plasma levels over 100 ng/l were also only found for galaxolide (4100 ng/l) and tonalide (800 ng/l). Women showed significantly higher levels than men. In a statistical multivariate approach only use of body lotion and age were predictive of positive galaxolide concentrations. For tonalide no significant predictor could be found. The findings mirror the replacement of nitro musk fragrances by polycyclic musks, mainly galaxolide. The high concentrations of galaxolide in human blood raise concern since few toxicological data are available.

Studies of drug binding to plasma proteins using a variant of equilibrium dialysis

The plasma protein binding of three model compounds was investigated using a variant of equilibrium dialysis, denoted comparative equilibrium dialysis (CED), and the results were compared with those obtained with ultrafiltration (UF). In CED, the buffer that the plasma is dialysed against in traditional equilibrium dialysis is replaced by, for example, plasma from other species. The CED method has the advantage that the unbound concentration (C(u)) does not need to be measured, which can be difficult for drugs with extremely small unbound fractions. Instead, the ratio of the total drug concentration (C(tot)) on either side of the dialysis membrane at equilibrium is a direct measure of the relative binding properties of the two plasma types. For the first model compound, having an unbound fraction (f(u)) of about 0.05% in human plasma, the time to reach equilibrium was too long (> or =40 h) to make the CED technique feasible in practice. For the second model compound, the more weakly bound drug NAD-299 (with an unbound fraction of about 2% in human plasma), the CED equilibration times were considerably shortened (< or =16 h), and the technique was applied to plasma from three different species. Large discrepancies between the CED and UF results were seen, CED always giving rise to much lower C(tot) differences than expected from the UF results. It is suspected that this discrepancy was due to equilibration between the dialysis chambers of all plasma components with a molecular weight less than the cut-off of the membrane. This equilibration causes altered binding properties compared to the initial plasma. When performing ultrafiltration on plasma where drug was added to untreated plasma or added to blank plasma that was equilibrated against plasma from the same or from another species, the change of binding properties was confirmed. To ensure that the results were not specific for NAD-299, a third model compound, tolterodine, was also included. The same trends as for NAD-299 were seen. Because of the long equilibration times for compounds with high protein binding and, in particular, the suspected partial mixture of low molecular weight compounds from the two plasma types and the subsequent change of binding properties, we cannot recommend the CED method as a tool for studying relative protein binding.

Antivascular and antitumor evaluation of 2-amino-4-(3-bromo-4,5-dimethoxy-phenyl)-3-cyano-4H-chromenes, a novel series of anticancer agents

A novel series of 2-amino-4-(3-bromo-4,5-dimethoxy-phenyl)-3-cyano-4H-chromenes was identified as potent apoptosis inducers through a cell-based high throughput screening assay. Six compounds from this series, MX-58151, MX-58276, MX-76747, MX-116214, MX-116407, and MX-126303, were further profiled and shown to have potent in vitro cytotoxic activity toward proliferating cells only and to interact with tubulin at the colchicine-binding site, thereby inhibiting tubulin polymerization and leading to cell cycle arrest and apoptosis. Furthermore, these compounds were shown to disrupt newly formed capillary tubes in vitro at low nanomolar concentrations. These data suggested that the compounds might have vascular targeting activity. In this study, we have evaluated the ability of these compounds to disrupt tumor vasculature and to induce tumor necrosis. We investigated the pharmacokinetic and toxicity profiles of all six compounds and examined their ability to induce tumor necrosis. We next examined the antitumor efficacy of a subset of compounds in three different human solid tumor xenografts. In the human lung tumor xenograft (Calu-6), MX-116407 was highly active, producing tumor regressions in all 10 animals. Moreover, MX-116407 significantly enhanced the antitumor activity of cisplatin, resulting in 40% tumor-free animals at time of sacrifice. Our results identify MX-116407 as the lead candidate and strongly support its continued development as a novel anticancer agent for human use.

Different effects of exercise on plasma concentrations of nebivolol, bisoprolol and carvedilol

BACKGROUND

In-vitro studies have shown that beta-blockers are taken up into and released from adrenergic cells together with epinephrine and norepinephrine. Consequently, studies in humans revealed an increase in plasma concentrations of propranolol and atenolol, whereas those of carvedilol were not affected by physical exercise. However, nebivolol and bisoprolol never were investigated on this issue.

METHODS

Ten healthy males received oral doses of 5 mg nebivolol, 5 mg bisoprolol, and 50 mg carvedilol daily for one week in a cross-over fashion. Exercise was performed at 3 hours following oral intake of the respective last drugs on the eighth day. Blood samples were taken at rest, during the last minute of exercise, and after 15 min of recovery.

RESULTS

At rest and during exercise, heart rates were as follows: Nebivolol, 57 +/- 7 and 137 +/- 11 beats/min; bisoprolol, 55 +/- 5 and 139 +/- 14 beats/min; carvedilol, 56 +/- 5 and 135 +/- 13 beats/min, with no significant differences between the drugs. Plasma concentrations were as follows: Nebivolol-rest 0.273 +/- 0.029 ng/ml, exercise 0.274 +/- 0.035 ng/ml, recovery 0.272 +/- 0.035 ng/ml (n.s.). Bisoprolol-rest 4.99 +/- 2.73 ng/ml, exercise 6.49 +/- 5.58 ng/ml, recovery 4.90 +/- 3.06 ng/ml ( p < 0.01). Carvedilol-rest 10.3 +/- 9.3 ng/ml, exercise 9.7 +/- 8.2 ng/ml, recovery 6.5 +/- 5.6 ng/ml ( p < 0.05).

DISCUSSION

Plasma concentrations of bisoprolol increased during exercise and returned to baseline during recovery, a behaviour which would have been predicted according to present knowledge. However, exercise had no effect on plasma concentrations of nebivolol and carvedilol, a finding that is in contrast to previous results with other beta-blockers such as propranolol and atenolol. We conclude that both nebivolol and carvedilol are not taken up into and released from adrenergic nerves during exercise, a feature that clearly distinguishes these drugs from other beta-blockers so far investigated.

Differences in the pharmacokinetics of peroxisome proliferator-activated receptor agonists in genetically obese Zucker and sprague-dawley rats: implications of decreased glucuronidation in obese Zucker rats

Genetically obese Zucker rats exhibit symptoms similar to those of obese patients with insulin-resistance or Type II diabetes; therefore, they have been used as a genetic model to study obesity, as well as a pharmacological model for the discovery of new drugs for the treatment of Type II diabetes and hyperlipidemia. In the present study, we compared the pharmacokinetics of two novel peroxisome proliferator-activated receptor (PPAR) agonists, MRL-I [(2R)-7-[3-[2-chloro-4-(4-fluorophenoxy)phenoxy]propoxy]-2-ethyl-3,4-dihydro-2H-benzopyran-2-carboxylic acid] and MRL-II [(2R)-7-[3-[2-chloro-4-(2,2,2-trifluoroethoxy)phenoxy]propoxy]-3,4-dihydro-2-methyl-2H-benzopyran-2-carboxylic acid], in obese Zucker and lean Sprague-Dawley rats following a single intravenous administration. The plasma clearance of both MRL-I and MRL-II was significantly lower in obese Zucker rats (4- and 2-fold, respectively) compared with Sprague-Dawley rats, but without any significant change in the volume of distribution, which resulted in a dramatic increase in the half-life (7- and 3-fold, respectively). The reversible in vitro plasma protein binding of [(14)C]MRL-I and [(14)C]MRL-II was comparable in the two strains, approximately 96% bound. The expression levels of uridine diphosphate-glucuronosyltransferases 1A1, 1A6, 2B1, and CYP2C11 and 3A1 mRNA in liver were lower (30-50%) in Zucker compared with Sprague-Dawley rats, as were the liver glutathione S-transferases (70%), quinone reductase (30%), organic anion-transporting protein 2 (80%), and multidrug resistance-associated protein 2 (Mrp2) (50%) mRNA levels. However, Mrp3 mRNA levels were similar in both strains. Consistent with these observations, the intrinsic clearance (CL(int)), calculated from the V(max)/K(m) of glucuronidation of [(14)C]MRL-I and [(14)C]MRL-II in liver microsomes, was approximately 2-fold lower in obese Zucker rats; the K(m) values were comparable in the two strains for both compounds. In conclusion, differences in the pharmacokinetics of two novel PPAR agonists, both cleared, predominantly, by conjugation, were evident in genetically obese Zucker rats compared with Sprague-Dawley rats. These differences were consistent with changes in the mRNA levels of hepatic drug-metabolizing enzymes and transporters. This information should be considered when comparing pharmacokinetic and efficacious doses in the obese Zucker rats, used as a pharmacological model, with those in Sprague-Dawley rats, which are used widely for drug metabolism and toxicology studies.

Simultaneous determination of the novel neuroprotective agent KR-31378 and its metabolite KR-31612 using high performance liquid chromatography with tandem mass spectrometry in human plasma

An LC/MS/MS method for the simultaneous determination of a neuroprotective agent for ischemia-reperfusion damage, KR-31378 and its N-acetyl metabolite KR-31612 in human plasma was developed. KR-31378, KR-31612 and the internal standard, KR-31543 were extracted from human plasma by liquid-liquid extraction. A reverse-phase HPLC separation was performed on Luna phenylhexyl column with the mixture of acetonitrile-5 mM ammonium formate (55:45, v/v) as mobile phase. The detection of analytes was performed using an electrospray ionization tandem mass spectrometry in the multiple reaction monitoring mode. The lower limits of quantification for KR-31378 and KR-31612 were 2.0 ng/ml. The method showed a satisfactory sensitivity, precision, accuracy, recovery and selectivity.

Direct absorption of acylated anthocyanin in purple-fleshed sweet potato into rats

Absorption of acylated anthocyanins in purple-fleshed sweet potato (Ipomoea batatas cv. Ayamurasaki) in rats was studied to obtain evidence that the acylated anthocyanins themselves could exert a physiological function in vivo. Peonidin 3-caffeoylsophoroside-5-glucoside (Pn 3-Caf*sop-5-glc) in purple-fleshed sweet potato was directly absorbed into rat and present as an intact acylated form in plasma. After oral administration of the purple-fleshed sweet potato anthocyanin (PSA) concentrate containing 38.9 micromol of Pn 3-Caf*sop-5-glc/kg of body weight, Pn 3-Caf*sop-5-glc was detected in the plasma, and the C(max) value and t(max) were estimated as 50.0 +/- 6.8 nmol/Lof plasma and 30 min, respectively. Furthermore, the plasma antioxidant capacity was significantly elevated from 58.0 +/- 12.0 to 89.2 +/- 6.8 micromol of Trolox equivalent/L of plasma 30 min after the administration of the PSA concentrate.

Integrated effects of the vasodilating beta-blocker nebivolol on exercise performance, energy metabolism, cardiovascular and neurohormonal parameters in physically active patients with arterial hypertension

OBJECTIVE

The present study was designed to investigate the integrated effects of the beta-1-selective blocker with vasodilator properties, nebivolol, on systemic haemodynamics, neurohormones and energy metabolism as well as oxygen uptake and exercise performance in physically active patients with moderate essential hypertension (EH).

DESIGN AND METHODS

Eighteen physically active patients with moderate EH were included: age: 46.9 +/- 2.38 years, weight: 83.9 +/- 2.81 kg, blood pressure (BP): 155.8 +/- 3.90/102.5 +/- 1.86 mm Hg, heart rate: 73.6 +/- 2.98 min(-1). After a 14-day wash-out period a bicycle spiroergometry until exhaustion (WHO) was performed followed by a 45-min submaximal exercise test on the 2.5 mmol/l lactate-level 48 h later. Before, during and directly after exercise testing blood samples were taken. An identical protocol was repeated after a 6-week treatment period with 5 mg nebivolol/day.

RESULTS

Nebivolol treatment resulted in a significant (P < 0.01) decrease in systolic and diastolic BP and heart rate at rest and during maximal and submaximal exercise. Maximal physical work performance, blood lactate and rel. oxygen uptake (rel. VO(2)) before and after nebivolol treatment at rest and during maximal and submaximal exercise remained unaltered. Free fatty acid, free glycerol, plasma catecholamines, beta-endorphines and atrial natriuretic peptide (ANP) increased before and after treatment during maximal and submaximal exercise but remained unaltered by nebivolol treatment. In contrast, plasma ANP levels at rest were significantly higher in the presence of nebivolol, endothelin-1 levels were unchanged.

CONCLUSIONS

Nebivolol was effective in the control of BP at rest and during exercise in patients with EH. Furthermore, nebivolol did not negatively affect lipid and carbohydrate metabolism and substrate flow. The explanation for the effects on ANP at rest remain elusive. This pharmacodynamic profile of nebivolol is potentially suitable in physically active patients with EH.

Repetitive cortical spreading depression in a gyrencephalic feline brain: inhibition by the novel benzoylamino-benzopyran SB-220453

Transient cortical depolarization is implicated in the pathology of migraine. SB-220453 is a potent anti-convulsant which inhibits neurogenic inflammation and cortical spreading depression (SD)-evoked nitric oxide release via a novel but unknown mechanism. This study further investigates the effects of SB-220453 on generation and propagation of repetitive SD in the anaesthetized cat. Vehicle or SB-220453 1, 3 or 10 mg/kg was administered intraperitoneally 90 min prior to induction of SD in the suprasylvian gyrus (SG). Changes in d.c. potential were recorded in the SG and the adjacent marginal gyrus (MG). In vehicle-treated animals (n = 7), a brief exposure (6 min) to KCl induced a median (25-75% range) number of five (four to six) and three (two to four) depolarizations over a duration of 55 min (32-59 min) and 51 min (34-58 min) in the SG and MG, respectively. SB-220453 produced dose-related inhibition of the number of events and period of repetitive SD activity. SB-220453 also reduced SD-induced repetitive pial vasodilatation but had no effect on resting haemodynamics. However, when SD events were observed in the presence of SB-220453, it had no effect on metabolic coupling. These results show that SB-220453 produces marked inhibition of repetitive SD in the anaesthetized cat. SB-220453 may therefore have therapeutic potential in treatment of SD-like activity in migraine.

Trace-level quantitation of iralukast in human plasma by microbore liquid chromatography/tandem mass spectrometry

Iralukast (CGP 45715A) is a potent peptido-leukotriene antagonist that is active in various in vitro and animal models for the treatment of asthma. An analytical challenge was to develop a sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) method with a lower limit of quantitation (LLOQ) of 10 pg/mL for the analysis of iralukast when administered at low doses during clinical trials. Several issues had to be addressed in order to devise a LC/MS/MS assay for the above compound. First, iralukast appeared to be light sensitive and unstable at room temperature under acidic conditions. Second, a LLOQ of 10 pg/mL was needed to support several clinical trials. Third, positive electrospray ionization of iralukast did not yield the necessary sensitivity required for studies in humans. Consequently, LC/MS/MS conditions were optimized for the negative ion mode of detection. Fourth, sample preparation steps proved to be critical to reduce the possibility of microbore HPLC column (50 mm x 1.0 mm i.d.) obstruction, chromatographic deterioration, and matrix-mediated electrospray ion suppression. While our validated method addressed the above challenges, its major drawback was limited sample throughput capability. Nonetheless, plasma concentration-time profiles for patients with moderate asthma after oral administration of 200, 500, 1000, and 5000 microgram/kg/day of iralukast were successfully obtained.

[Acute beta 1-selective beta-receptor blocker nebivolol poisoning in attempted suicide]

HISTORY AND ADMISSION FINDINGS

A 17-year-old girl had swallowed 80-100 tablets of Nebivolol, 5 mg each, with suicidal intent. She was referred to hospital 8 hours later by an emergency duty physician. On admission she was sweaty and pale, but there were no other obvious abnormalities. Neurological examination revealed decreased responsiveness and slowed movements. She was known to have type 1 diabetes mellitus.

INVESTIGATIONS

Blood pressure was 105/55 mmHg, the ECG showed sinus bradycardia of 55 beats/min. Biochemical tests revealed hypoglycaemia (2.1 mmol/l), hypokalaemia (3.4 mmol/l) and respiratory failure (pO2 6.16 kPa, O2 saturation 82%, pCO2 6.55 kPA). Heart and lung were unremarkable on physical examination as were chest radiogram and echocardiogram. Plasma level of nebivolol was 480 ng/ml on admission (therapeutic range 88-195 ng/ml).

TREATMENT AND COURSE

After gastric lavage and administration of charcoal and sodium sulphate a temporary pacemaker was connected and glucagon infused intravenously as an antidote. The cardiovascular state stabilized with falling plasma level of nebivolol. Glucose was administered initially, but transient intravenous insulin infusion became necessary to counteract hyperglycaemia. The patient was transferred from the intensive care unit in a stable cardiovascular state after 2 days.

CONCLUSION

This case demonstrates that swallowing 400-500 mg nebivolol, resulting in a plasma level of 480 ng/ml, need not be fatal. But the outcome in this patient should not be taken as necessarily applying to similar cases. It depends on the individual patient's metabolic state whether higher plasma levels might be reached with the same amount of ingested nebivolol.

Liquid chromatographic determination of a non-steroidal oral contraceptive CDRI-85/287 in rat serum

A precise and sensitive high performance liquid chromatographic (HPLC) assay method was developed and validated for the quantitation of 2-[4-(2-piperidinoethoxy) phenyl]-3-phenyl-(2H)-1-benzo(b)pyran (compound CDRI-85/287) in rat serum. This method, applicable to 0.5 ml volumes of serum, was validated according to GLP guidelines. It involved double extraction of serum samples with a mixture of hexane and iso-propanol (98:2 v/v) at alkaline pH and the use of UV detection at 332 nm. Linearity, precision and accuracy were acceptable (5-200 ng ml-1. The absolute recovery was more than 75% and the lower limit of quantitation was 5 ng ml-1. Freeze-thaw stability studies up to four cycles showed no apparent differences in the calculated spiked concentrations. However, in-process stability evaluation showed the stability of the processed samples lasted up to 85 h.

Pharmacokinetics and pharmacodynamics of the leukotriene B4 receptor antagonist CP-105,696 in man following single oral administration

AIMS

CP-105,696, (+)-1-(3S,4R)-[3-(4-phenylbenzyl)-4-hydroxy-chroman-7-yl] cyclopropane carboxylic acid is a potent, novel LTB4 receptor antagonist advanced to clinical trials to determine its efficacy in inflammatory diseases. The pharmacokinetics and pharmacodynamics of CP-105,696 were investigated in healthy male volunteers following oral administration of single doses of 5 to 640 mg.

METHODS

Forty-eight subjects participated in a randomized, double-blind, parallel group study. Plasma and urine concentrations of CP-105,696 were determined at intervals after drug administration. As an indication of LTB4 receptor antagonism following oral administration of CP-105,696, the inhibiton of LTB4-induced upregulation of the neutrophil cell surface complement receptor (CR3), CD11b/CD18, was monitored at 4 h following drug administration using an ex vivo whole blood flow cytometry assay.

RESULTS

Cmax and AUC(0, infinity) increased in a dose-related manner. Respective mean Cmax values were 0.54 to 30.41 microg ml(-1) following doses of 5 to 640 mg. Respective mean AUC(0, infinity) values were 1337 to 16819 microg ml(-1) h for the 40 to 640 mg dose groups. Plasma concentrations declined in a monoexponential manner, with terminal elimination half-lives ranging from 289 to 495 h. Group mean terminal elimination half-lives were dose-independent. Urinary excretion of unchanged drug accounted for < 1% of the administered dose. A linear relationship was observed between CP-105,696 plasma concentrations and inhibition of LTB4-mediated CD11b upregulation on human neutrophils in whole blood. CP-105,696 plasma concentrations of 5-6 microg ml(-1) were necessary to elicit a two-fold shift to the right of the LTB4 concentration response curve for CD11b upregulation.

CONCLUSIONS

These studies demonstrate pharmacologically significant LTB4-receptor antagonism following a single dose of CP-105,696 and pharmacokinetics consistent with once-daily dosing.

Combined effects of dehydroepiandrosterone and EM-800 on bone mass, serum lipids, and the development of dimethylbenz(A)anthracene-induced mammary carcinoma in the rat

Although treatment with dehydroepiandrosterone (DHEA) and the antiestrogen EM-800 alone decreased dimethylbenz(A)anthracene (DMBA)-induced mammary tumor incidence from 95% to 57% and 38%, respectively, approximately 9 months after DMBA administration, only two tumors developed in the group of animals that received the combination of DHEA and EM-800, and these two tumors disappeared before the end of the experiment (P < 0.01 vs. DHEA or EM-800 alone). Average tumor number per tumor-bearing animal as well as average tumor area per tumor-bearing animal were further decreased in animals that received the combination therapy compared with the effect of each treatment alone (P < 0.01). DHEA induced 6.9% (P < 0.01), 10.6% (P < 0.05), and 8.2% (P < 0.01) increases in bone mineral density of total skeleton, lumbar spine, and femur, respectively. The addition of EM-800 to DHEA did not affect the enhancing effect of DHEA on bone mass. The combination of the two drugs had important inhibitory effects on the urinary excretion of calcium and phosphorus as well as on the urinary hydroxyproline/creatinine ratio. Serum total alkaline phosphatase was stimulated by DHEA. Treatment with EM-800 decreased both serum triglyceride and cholesterol levels, whereas DHEA had an inhibitory effect on serum triglycerides. Although treatment with EM-800 caused a marked atrophy of the mammary gland, DHEA alone reduced lobular hyperplasia seen in aged intact rats while causing an androgen-specific stimulation of the same structures in animals already receiving the antiestrogen EM-800. The combination of DHEA and EM-800 lowered ovarian weight by 24% (P < 0.01) and decreased serum estradiol concentrations to intact control levels, whereas each compound alone had no effect on ovarian weight and stimulated serum estradiol levels by 45% (P < 0.05) and 46% (P < 0.05), respectively. Treatment with EM-800 caused a marked inhibition of uterine and vaginal weight. The present data show the additive inhibitory effects of DHEA and EM-800 on the development of DMBA-induced mammary carcinoma in the rat, thus suggesting the potential benefits of such a combination for the prevention of breast cancer in women while preserving or even increasing bone mass and maintaining a favorable lipid profile.

Simultaneous determination of a potassium channel opener and its metabolite in rat plasma with column-switching liquid chromatography using atmospheric pressure chemical ionisation

A specific LC-MS assay was developed for simultaneous determination of Ro 31-7837 (I) and its metabolite Ro 31-6930 (II) in rat plasma, using on-line SPE by column-switching reversed-phase HPLC combined with atmospheric pressure chemical ionization (APCI) tandem mass spectrometry for detection in the selected reaction monitoring mode. The method involved precipitation of plasma proteins with ethanol and automatic injection of a 1-ml aliquot of the supernatant onto a standard bore trapping column (LC-ABZ, 20x4.6 mm) for compound retention. Using the backflush mode, the analytes were transferred onto the analytical column (Kromasil C18, 125x4.0 mm) for chromatographic separation and mass spectrometric detection. The mean precision and accuracy for I and II in the concentration range 0.25-100 ng/ml were found to be 3.7% and 101%, and 3.5% and 106%, respectively. The data were assessed from QC samples during the validation phase of the assay. The lower limit of quantification for both I and II was 0.25 ng/ml, using a 0.5-ml plasma aliquot. This LC-MS method provided the requisite specificity, sensitivity, accuracy and precision to assess the pharmacokinetics of the compounds in the rat.

A pharmacokinetic and pharmacodynamic interaction study between nebivolol and the H2-receptor antagonists cimetidine and ranitidine

AIMS

The study was designed to investigate the effects of the H2-receptor antagonists, cimetidine and ranitidine on the pharmacokinetics and pharmacodynamics of nebivolol in healthy volunteers.

METHODS

Twelve healthy volunteers took part in a randomized placebo-controlled cross-over study. Each subject received on three separate occasions placebo, cimetidine (400 mg twice daily) or ranitidine (150 mg twice daily) for 24 h before and 48 h after a single oral dose of nebivolol (5 mg). Nebivolol and its individual (+) and (-) enantiomers were determined tby h.p.l.c.

RESULTS

Ranitidine had no significant effect on nebivolol pharmacokinetics. Cimetidine, however, resulted in a 21-23% increase in Cmax of unchanged nebivolol and of each enantiomer plus its hydroxylated metabolites. Cimetidine significantly (p < 0.05) increased the AUC [mean +/- s.d. (95% C.I. of differences in mean)] for unchanged (+/-)-nebivolol [7.76 +/- 3.07 ng ml-1 h with placebo; 11.50 +/- 5.40 (1.75, 8.76) ng ml-1 h with cimetidine], (+)-nebivolol plus its hydroxylated metabolites [73.0 +/- 18.0 ng ml-1 h with placebo; 91.5 +/- 25.7 (1.0, 23.1) ng ml-1 h with cimetidine] and (-)-nebivolol plus its hydroxylated metabolites [101 +/- 32 ng ml-1 h with placebo; 123 +/- 38 (3.3, 27.0) ng ml-1 h with cimetidine]. Statistical analysis of the resting blood pressure and heart rate and exercise data did not suggest any consistent effects of ranitidine or cimetidine upon the pharmacodynamic effects of nebivolol.

CONCLUSIONS

There was no interaction between ranitidine and nebivolol. Although cimetidine inhibited nebivolol metabolism, it did not have a significant influence on the pharmacodynamics of the drug.

Gastrointestinal physiology-regulated dogs for bioavailability evaluation of an oral controlled-release dosage form composed of pulsatile release granules

Gastrointestinal (GI) physiology-regulated beagle dogs (regulated dogs) were regulated by a combined treatment using intramuscular pentagastrin and intravenous atropine sulfate. In the regulated dogs, the gastric pH was shifted to around 2, and the GI transit time was prolonged to approximate that in humans. Pranoprofen, an acidic anti-inflammatory agent, was granulated around sucrose seeds, and then coated with low substituted hydroxypropyl cellulose used as a swelling agent to afford plain granules (A-granule). Then, A-granule was coated stepwise with ethyl cellulose used as an outer shell material to afford two kinds of pulsatile release granules (B- and C-granules). In the dissolution study using pH 1.2 and 6.8 media, A-, B- and C-granules exhibited lag times of 0, 1 and 2h, respectively. Even in intact beagle dogs, the absorption profiles for A- and B-granules corresponded with those expected from the dissolution profiles. In contrast, the bioavailability of C-granule was only 35% in the intact dogs, but was 55% in the regulated dogs. Thus, the absorption of pranoprofen from pulsatile release granules after a longer lag time should be influenced by the location in the GI tract. Next, a controlled-release (CR) dosage form of pranoprofen was tentatively prepared by combining A-, B- and C-granules at the ratio of 3:4:3 (w/w in contents of pranoprofen). The bioavailability of the CR dosage form was significantly diminished in the intact dogs, being about 70% as much as that in the regulated dogs. Therefore, the regulated dogs would be superior to the intact dogs in avoiding the underestimation of the bioavailability of a CR dosage form with a pulsatile release property.

BMS-180448, a novel glyburide-reversible cardioprotective agent, enhances postischemic recovery of contractile function in dogs

BMS-180448 has been found to retain the cardioprotective potency of its chemically related analog, cromakalim, although having significantly less peripheral vasodilating activity. The effect of the ATP-sensitive potassium channel opener, BMS-180448, on postischemic recovery of function (segmental shortening) was determined in open chested, anesthetized dogs instrumented with ultrasonic crystals. The plasma concentration of the effective and ineffective doses of BMS-180448 was compared to concentrations used in isolated rat hearts. BMS-180448 was given as a total dose of 4.2, 1.4 or 0.5 mg/kg over 30 min, starting 15 min before ischemia. Ischemia was initiated by a complete occlusion of the left anterior descending coronary artery for 15 min. Reperfusion was maintained for 3 hr and segmental shortening was measured. During ischemia, systolic bulging was observed in the ischemic region in drug- and vehicle-treated groups. Upon reperfusion, some contractile functional recovery was observed in vehicle-treated controls within minutes, but quickly decreased so that slight bulging was observed up to 3 hr into reperfusion. High dose BMS-180448 significantly improved the recovery of contractile function such that, by 3 hr after reperfusion, segmental shortening had recovered to 60% of base line. The 1.4-mg/kg dose also significantly improved reperfusion function, but 0.5 mg/kg of BMS-180448 was without effect. None of the doses of BMS-180448 significantly affected peripheral hemodynamic status or collateral blood flow. The plasma concentration of the 1.4-mg/kg dose was approximately 3 microM during ischemia. In isolated rat hearts, BMS-180448 significantly increased postischemic function at 3 microM and higher concentrations, which agrees with the dog data. BMS-180448 was protective in a dose-dependent manner in a canine model of stunned myocardium, and the concentrations necessary for protection are similar to that for rats.

The development and cross-validation of methods based on radioimmunoassay and LC/MS-MS for the quantification of the class III antiarrhythmic agent, MK-0499, in human plasma and urine

An analytical method based on radioimmunoassay (RIA) has been developed for the determination of the antiarrhythmic agent, MK-0499, in plasma and urine. Owing to the potency of the drug, the specificity of this assay in human plasma could not be adequately determined using conventional RIA procedures. A highly specific procedure, based on LC/MS-MS, was developed to cross-validate the RIA. The lower quantifiable limits of the RIA and LC/MS-MS-based methods were 0.05 and 0.013 ng ml-1, respectively. Cross-validation data, compared using paired student's t-test regression analysis, showed excellent correlation between methods. The mass spectrometric assay was also used to simultaneously measure plasma concentrations of unlabeled and 14C-labeled MK-0499 following administration of the drug at high specific activity to volunteers.

Stereospecific high-performance liquid chromatographic determination of an S(-)-benzopyran methyl ester derivative (CGP 50 068), its (-)-carboxylic acid metabolite (CGP 55 461) and the related (+)-enantiomer (CGP 54 228) in human and dog plasma

The simultaneous determination of CGP 50 068, S(-)-enantiomer (I), its (-)-carboxylic acid metabolite CGP 55 461 (II) and the related (+)-enantiomer CGP 54 228 (III) by stereospecific high-performance liquid chromatography, in human plasma, is described. The three compounds and racemic acebutolol, used as internal standard, were isolated from plasma by liquid-solid extraction on disposable C18 columns. The resolution and determination of I and the two carboxylic acid enantiomers were achieved by direct chromatography using a Chiral-AGP column refrigerated at 5 degrees C. The mobile phase was tetrabutylammonium iodide in a pH 7 phosphate buffer solution used at a constant flow-rate of 0.5 ml/min. The UV detection wavelength was set at 270 nm. The reproducibility and accuracy of the method were found to be suitable over the concentration range 0.56-28.0 mumol/l for II and III and 2.0-26.7 mumol/l for I.

High-performance liquid chromatographic measurement of the novel anti-HIV agent 7,8-dihydrocostatolide (NSC 661123)

An HPLC assay was used to determine levels of a promising anti-HIV agent 7,8-dihydrocostatolide (DC; NSC 661123) in human and murine plasma. The structurally related compound costatolide (C) was found to be a suitable internal standard. Drug was extracted from human or murine plasma using a solid-phase C18 cartridge. The compound was eluted from an ODS analytical HPLC column using an acetonitrile-water mobile phase. Drug was quantified over the assay range of 19.5 to 625 ng/ml with excellent within- and between-day reproducibility. Data resulting from the use of the assay method for determination of dihydrocostatolide pharmacokinetics in mice are presented. This is the first report of a validated HPLC assay for determining DC levels in human and mouse plasma.

Pharmacokinetic behaviour in polymorphonuclear leucocytes of N,N-dimethylcarbamoylmethyl alpha,2-dimethyl-5H-[1]benzopyrano[2,3-b]- pyridine-7-acetate (Y-23023), a new prodrug type of anti-inflammatory agent, and indomethacin after oral administrations in rats

N,N-Dimethylcarbamoylmethyl alpha,2-dimethyl-5H-[1]- benzopyrano[2,3-b]pyridine-7-acetate (Y-23023) is a prodrug developed as a new non-steroidal anti-inflammatory drug (NSAID). Y-23023 is rapidly hydrolysed to an active metabolite, alpha,2-dimethyl-5H-[1]benzopyrano[2,3-b]pyridine-7-acetic acid (M1) following its absorption and then exhibits a strong anti-inflammatory activity. We have examined the pharmacokinetic behaviour in polymorphonuclear leucocytes (PMNs) of M1 and of indomethacin after oral administration to rats of Y-23023 and indomethacin, respectively. Y-23023 was rapidly absorbed, producing a mean Cmax (1.13 micrograms mL-1) of M1 after 1 h in plasma. Indomethacin was less rapidly absorbed, producing a mean Cmax (3.38 micrograms mL-1) after 3 h in plasma. The mean AUC of M1 and indomethacin in plasma were 5.45 micrograms h mL-1 and 22.49 micrograms h mL-1, respectively. The mean tmax, Cmax and AUC of M1 in PMNs were 1 h, 11.1 ng (41 pmol)/10(8) cells and 58.6 ng (164 pmol) h/10(8) cells, respectively. The same parameters for indomethacin in the PMNs were 3 h, 15.4 ng (57 pmol)/10(8) cells and 95.2 ng (266 pmol) h/10(8) cells, respectively. The PMNs/plasma ratio of M1 was about 2.8 times that of indomethacin. These results indicate that the association of M1, an active metabolite of Y-23023, from blood to the PMNs is greater than that of indomethacin.

Reduction in myocardial infarct size by the new potassium channel opener bimakalim

We examined the effect of a new potassium channel opener, bimakalim, on myocardial infarct size (IS) in dogs. Barbital-anesthetized dogs were subjected to 90 min of left circumflex coronary artery (LCX) occlusion followed by 5-h reperfusion. Bimakalim (3 micrograms/kg bolus followed by 0.1 microgram/kg/min intravenously, i.v.) was initiated either 15 min before LCX occlusion and continued throughout the experiments in one group of animals or initiated 5 min before and throughout reperfusion in a second group. A third group of dogs received i.v. vehicle (control) 15 minutes before LCX occlusion and throughout the remainder of the experiment. IS was determined by triphenyltetrazolium histochemical staining, regional myocardial blood flow (RMBF) by the radioactive microsphere technique, and neutrophil migration by measurement of tissue myeloperoxidase (MPO) activity. Bimakalim reduced mean aortic blood pressure (MBP, 25 mm Hg) during the occlusion and reperfusion periods in the group of dogs that received the drug throughout the experiment and reduced in BP, during reperfusion when administered immediately before the reperfusion period. In addition, bimakalim increased LCX coronary artery blood flow (CBF) and increased regional myocardial blood flow (RMBF) primarily during reperfusion in both drug-treated groups, with the greatest increase to the subepicardial region. During occlusion, however, bimakalim had no effect on collateral blood flow to the ischemic region. In all three groups, left ventricular (LV) mass, area at risk (AAR) mass, and percentage of he left ventricle at risk were similar.(ABSTRACT TRUNCATED AT 250 WORDS)

Determination of the anti-ischemic activity of nebivolol in comparison with atenolol

The anti-ischemic effect of 5 mg nebivolol o.i.d., a newly developed beta 1-selective adrenoceptor blocking drug with vasodilating properties, was compared with that of atenolol (100 mg o.i.d.) following a treatment period of 6 days. The study was performed in 24 patients with documented coronary artery disease and stable angina pectoris according to a double-blind randomized study, designed using conventional symptom-limited exercise testing. Exercise testing 3 h after the first dose showed a more marked ST-segment reduction by atenolol than by nebivolol (59% vs. 18%). ST-segment depression measured 24 h after administration of the penultimate dose was statistically significantly reduced by nebivolol (from 0.19 +/- 0.07 to 0.13 +/- 0.07 mV; P = 0.0059) but not by atenolol (from 0.17 +/- 0.06 to 0.14 +/- 0.10 mV; P = 0.0703). Approximately 3 h after the last dose, the reduction was comparable (45% and 38% by nebivolol and atenolol, respectively). Exercise duration, exercise time necessary to produce ST-segment depression by 0.1 mV and exercise time to the onset of angina were also prolonged following administration of both drugs. Thus, at steady-state single daily doses of 100 mg atenolol and 5 mg nebivolol were about equieffective when measured at time of maximal effect (i.e. 3 h after drug administration). However, duration of action with respect to the ST-segment depression seems to be slightly longer for nebivolol.

Stereoselective disposition of pranoprofen, a nonsteroidal antiinflammatory drug, in rabbits

The stereoselective disposition of pranoprofen, a nonsteroidal antiinflammatory drug, was studied in rabbits. Plasma levels of S(+)-pranoprofen after oral and i.v. administration of the racemate pranoprofen were always higher than those of the R(-)-isomer. The elimination rate constant of the R(-)-isomer (2.74 h-1), calculated using a 2-compartment model, was significantly larger than that of the S(+)-isomer (2.14 h-1), while no significant difference was observed in the absorption rate constants between enantiomers. Pranoprofen was excreted in the urine exclusively in the form of pranoprofen glucuronide. The glucuronide of R(-)-isomer was excreted more rapidly than the S(+)-isomer. However, no metabolite of pranoprofen was detected in plasma, owing to its instability in liver and plasma. Moreover, the elimination of the S(+)- and R(-)-isomers of pranoprofen was more rapid when the enantiomers were separately administered than when administered as the racemate. The R(-)-isomer showed a significantly higher elimination rate than the S(+)-isomer, compared to what was observed upon the administration of the racemate. No inversion to an R(-)-form or S(+)-form to their corresponding antipode after administration of the isomers separately was detected. Pranoprofen, especially the R(-)-isomer, was significantly distributed in the kidney. An in vitro metabolism experiment of pranoprofen showed the predominant glucuronidation to be in the kidney rather than in the liver because of rapid hydrolysis of glucuronide in the liver.(ABSTRACT TRUNCATED AT 250 WORDS)

Study of interaction of pranoprofen with human serum albumin: binding properties of enantiomers and metabolite

The interaction of pranoprofen, pranoprofen glucuronide and pranoprofen methylester with human serum albumin (HSA), was investigated by equilibrium dialysis and spectroscopic techniques. The binding affinities of pranoprofen glucuronide and pranoprofen methylester to HSA were found to be almost the same, although they were remarkably small as compared to that of the parent compound, pranoprofen. Pranoprofen and pranoprofen methylester showed stereoselective affinities to HSA. It was found from the competitive displacement experiments using the fluorescent probes that the specific binding site for pranoprofen was site II, the diazepam site, and that the binding sites of pranoprofen glucuronide and pranoprofen methylester were site I, the warfarin site. In addition, from the binding data with modified HSA, it seemed that tyrosine-411 was specifically involved in the pranoprofen binding. The absorption spectral changes which accompanied the binding of pranoprofen and pranoprofen methylester to HSA or detergents implied that the HSA binding site of pranoprofen consisted of a cationic site on the surface of the albumin molecule with a hydrophobic region to accommodate the aromatic ring and that the binding site for pranoprofen methylester seemed to occupy a wide hydrophobic area. These limited data indicated differences in the location and microenvironments of binding sites for pranoprofen and its glucuronide on the HSA molecule.

Quantitative determination of CGS 18102A, a new anxiolytic, in human plasma using capillary gas chromatography/mass spectrometry

CGS 18102A is a novel hexahydrobenzopyranopyridine that has a mixed pharmacological profile of 5-HT-1A agonist and 5-HT-2 antagonist properties. Based upon these mechanisms, the compound is predicted to have anxiolytic efficacy with possible efficacy in depression. Preclinical studies in the rat have shown the drug to be well absorbed and extensively metabolized. Because of the anticipated low plasma levels in humans a gas chromatography/mass spectrometry (GC/MS) analytical method has been developed and validated to determine plasma concentrations of CGS 18102A in early clinical studies. The method utilizes CGS 18416A as the internal standard. Samples (1 mL) were extracted with pentane:ethyl acetate (75:25, v:v). Extracts were then concentrated and analysed directly by GC/MS. Separation was accomplished on a methylsilicone capillary column (30 m x 0.32 mm i.d.). GC/MS was carried out under positive ion ammonia CI conditions, with selected ion monitoring of the [M + H]+ ions (m/z = 262 and 248) for CGS 18102A and CGS 18416A, respectively. The method was successively applied to the analysis of clinical samples from an ascending multidose safety and tolerability study conducted in six normal healthy male volunteers.

Disposition of the enantiomers of cromakalim in rat and cynomolgus monkey

1. Disposition of the 3R,4S(+) and 3S,4R(-) enantiomers of the racemic antihypertensive drug cromakalim has been studied in rats and cynomolgus monkeys using the 14C-drug labelled in either the 3R,4S(+) or the 3S,4R(-) enantiomer. 2. After oral administration to rat, blood concentrations of the 3R,4S(+) enantiomer were up to fourfold higher than those of the 3S,4R(-) enantiomer. Metabolism of the former was not as extensive as that of the latter and consequently plasma and urinary radiometabolite patterns were quantitatively different. 3. In contrast to rat, there were much greater differences in the disposition of the two enantiomers following oral administration of cromakalim to the cynomolgus monkey. Plasma concentrations of the 3R,4S(+) enantiomer were approximately 100 x those of the 3S,4R(-) enantiomer and the rate of urinary 14C elimination for the 3R,4S(+) enantiomer was much faster than that for the 3S,4R(-) enantiomer. Plasma and urinary radiometabolite patterns were very different for the two isomers. Metabolic end products of the 3R,4S(+) enantiomer were predominantly phase I metabolites whereas the 3S,4R(-) enantiomer was almost entirely metabolized by glucuronidation. 4. A study of the racemic drug alone would have led to a misunderstanding of the fate of the compound in these species.