Determination of terbutaline enantiomers in human urine by capillary electrophoresis using hydroxypropyl-β-cyclodextrin as a chiral selector

A method for the determination of terbutaline enantiomers in human urine by capillary electrophoresis has been developed. Optimum resolution was achieved using 50 mM phosphate buffer, pH 2.5, containing 15 mM of hydroxypropyl-beta-cyclodextrin as a chiral selector. Urine samples were prepared by solid-phase extraction with Sep-pak silica, followed by CE. The assay was linear between 2-250 ng/mL (R = 0.9998 for (S)-(+)-terbutaline and R = 0.9999 for (R)-(-)terbutaline) and detection limit was 0.8 ng/mL. The intra-day variation ranged between 6.3 and 14.5% in relation to the measured concentration and the inter-day variation was 8.2-20.1%. It has been applied to the determination of (S)-(+)terbutaline and (R)-(-)-terbutaline in urine from healthy volunteer dosed with racemic terbutaline sulfate.     

Stereoselective analysis of carvedilol in human plasma and urine using HPLC after chiral derivatization

An enantioselective high-performance liquid chromatographic method for the analysis of carvedilol in plasma and urine was developed and validated using (-)-menthyl chloroformate (MCF) as a derivatizing reagent. Chloroform was used for extraction, and analysis was performed by HPLC on a C18 column with a fluorescence detector. The quantitation limit was 0.25 ng/ml for S(-)-carvedilol in plasma and 0.5 ng/ml for R(+)-carvedilol in plasma and for both enantiomers in urine. The method was applied to the study of enantioselectivity in the pharmacokinetics of carvedilol administered in a multiple dose regimen (25 mg/12 h) to a hypertensive elderly female patient. The data obtained demonstrated highest plasma levels for the R(+)-carvedilol (AUC(SS) (0-12) 75.64 vs 37.29 ng/ml). The enantiomeric ratio R(+)/S(-) was 2.03 for plasma and 1.49 for urine (Ae(0-12) 17.4 vs 11.7 microg).     

Steady-state pharmacokinetics of carvedilol and its enantiomers in patients with congestive heart failure

Carvedilol is a relatively new drug with beta- and alpha 1-receptor blocking activity and antioxidant effects recently approved for the treatment of congestive heart failure (CHF). An ascending, multiple-dose study was completed in 20 male patients with stable New York Heart Association (NYHA) Class III or IV CHF. The pharmacokinetics of carvedilol, S(-)-carvedilol, R(+)-carvedilol, and the active metabolites of carvedilol was assessed at steady state after twice-daily oral administration of carvedilol for 7 days at 6.25, 12.5, 25, and 50 mg doses. Carvedilol exhibited stereoselective pharmacokinetics in CHF patients with dose-proportional increases in steady-state plasma concentrations of carvedilol and its enantiomers. Mean AUC and Cmax values for carvedilol were up to twofold higher in patients with Class IV CHF as compared to those with Class III CHF. Steady-state plasma concentrations of the active metabolites also increased in a dose-proportional manner and were typically 10% or less of that observed for carvedilol. In general, carvedilol was adequately tolerated by adult male CHF patients at the dose levels (6.25-50 mg) evaluated in this study as adverse events were consistent with those frequently observed in patients with CHF.     

Development and validation of a capillary electrophoresis method for the enantiomeric purity determination of RS86017 using experimental design

A selective capillary electrophoresis method for determination of enantiomeric purity of RS86017, a new antiarrhythmic agent with two chiral centers, was developed and validated using sulfobutyl ether-β-cyclodextrin as chiral selector. The concentration of the chiral selector and organic modifier, pH of background electrolyte (BGE), capillary temperature, and applied voltage were systematically optimized by using orthogonal design and concentration of chiral selector was further optimized. The optimal conditions included 25mM phosphate buffer at pH 8.0, containing 28mg/mL sulfobutyl ether-β-cyclodextrin and 20% acetonitrile as running buffer, an applied voltage of 22kV, and a temperature of 20°C. The detection wavelength was 206nm. The obtained method was capable of separating RS86017 from its potential chiral impurities, the S,R-enantiomer, the R,R-diastereomer and the S,S-diastereomer with a short analysis time of 10min. The separation was validated with respect to its selectivity, repeatability, linearity, precision, accuracy, limits of detection (LOD), limits of quantitation (LOQ) and robustness testing. The LODs and LOQs were 0.8μg/mL and 2.5μg/mL for all isomers of RS86017, respectively. Finally, the method was used to investigate the chiral purity of RS86017 in bulk samples.     

2-甲基-β-环糊精作为手性选择剂对5种药物对映体的毛细管电泳拆分研究

目的以2-甲基-β-环糊精(2-O-methylated-β-cyclodextrin,2-O-M-β-CD)为手性添加剂,利用毛细管电泳法(capillary electrophoresis,CE)对消旋体药物甲溴后马托品、氧氟沙星、酮康唑、利阿唑和卡维地洛进行拆分研究。方法考察了背景电解质溶液的pH值、2-O-M-β-CD浓度、缓冲盐浓度对分离的影响,优化了分离条件。结果在最佳分离条件下,甲溴后马托品、氧氟沙星、酮康唑、利阿唑对映体达到完全分离,分离度分别为3.6、2.8、1.7、1.5;卡维地洛对映体分离度达到1.4。结论所建立的毛细管电泳法适于除卡维地洛外其余4种药物的对映体分离。     

Enantioselective quantification of carvedilol in human plasma by HPLC in heavily medicated heart failure patients

A simple, specific, sensitive, inexpensive and rapid HPLC method for enantioselective quantification of carvedilol in human plasma was developed in this study. S(−)- and R(+)-carvedilol and R(+)-propranolol as the internal standard were extracted from human plasma by liquid–liquid extraction using methyl tert-butyl ether. Enantioseparation was performed on a reverse-phase C18 Phenomenex Luna 5micron 150 mm × 2 mm column after chiral derivatization with 2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl isothiocyanate. The mobile phase was a mixture of water and acetonitrile. The peaks were detected using a fluorescence detector, where the excitation and emission wavelengths were set at 242 and 344 nm, respectively. The limits of quantification for the S(−)- and R(+)-carvedilol enantiomers were both 0.5 ng/ml. Combined intra- and inter-day variations for both enantiomers were less than 8.3%. The combined accuracy for both enantiomers ranged from 91.7 to 104.7%. This method was used to assay the carvedilol enantiomers in human plasma samples obtained from heavily medicated heart failure patients within the framework of a clinical trial.     

Chiral discrimination of sibutramine enantiomers by capillary electrophoresis and proton nuclear magnetic resonance spectroscopy

Capillary electrophoresis (CE) and proton nuclear magnetic resonance spectroscopy (¹H-NMR) have been used to discriminate the enantiomers of sibutramine using cyclodextrin derivatives. Possible correlation between CE and ¹H-NMR was examined. Good correlation between the ¹H-NMR shift non-equivalence data for sibutramine and the degree of enantioseparation in CE was observed. In CE study, a method of enantiomeric separation and quantitation of sibutramine was developed using enantiomeric standards. The method was based on the use of 50 mM of phosphate buffer of pH 3.0 with 10 mM of methyl-beta-cyclodextrin (M-β-CD). 0.05% of LOD, 0.2% of LOQ for S-sibutramine enantiomer was achieved, and the method was validated and applied to the quantitative determination of sibutramine enantiomers in commercial drugs. On a 600 MHz ¹H-NMR analysis, enantiomer signal separation of sibutramine was obtained by fast diastereomeric interaction with a chiral selector M-β-CD. For chiral separation and quantification, N-methyl proton peaks (at 2.18 ppm) were selected because of its being singlet and simple for understanding of diastereomeric interaction. Effects of temperature and concentration of chiral selector on enantiomer signal separation were investigated. The optimum condition was 0.5 mg/mL of sibutramine and 10 mg/mL of M-β-CD at 10°C. Distinguishment of 0.5% of S-sibutramine in R-sibutramine was found to be possible by ¹H-NMR with M-β-CD as chiral selector. Host-guest interaction between sibutramine and M-β-CD was confirmed by ¹H-NMR studies and CE studies. A Structure of the inclusion complex was proposed considering ¹H-NMR and 2D ROESY studies.     

Mutual inhibition between carvedilol enantiomers during racemate glucuronidation mediated by human liver and intestinal microsomes

Carvedilol is administered orally as a racemic mixture of R(+)- and S(-)-enantiomers for treatment of angina pectoris, hypertension and chronic heart failure. We have reported that enzyme kinetic parameters for carvedilol glucuronidation by human liver microsomes (HLM) differed greatly depending on the substrate form, namely, racemic carvedilol and each enantiomer. These phenomena were thought to be caused by mutual inhibition between carvedilol enantiomers during racemate glucuronidation. The aim of this study was to clarify the mechanism of these phenomena in HLM and human intestinal microsomes (HIM) and its relevance to uridine 5'-diphosphate (UDP)-glucuronosyl transferase (UGT) 1A1, UGT2B4 and UGT2B7, which mainly metabolize carvedilol directly in phase II enzymes. HLM apparently preferred metabolizing (S)-carvedilol to (R)-carvedilol in the racemate, but true activities of HLM for both glucuronidation were approximately equal. By determination of the inhibitory effects of (S)-carvedilol on (R)-carvedilol glucuronidation and vice versa, it was shown that (R)-carvedilol glucuronidation was more easily inhibited than was (S)-carvedilol glucuronidation. UGT2B7 was responsible for (S)-carvedilol glucuronidation in HLM. Ratios of contribution to (R)-carvedilol glucuronidation were approximately equal among UGT1A1, UGT2B4 and UGT2B7. However, enzyme kinetic parameters were different between the two lots of HLM used in this study, depending on the contribution ratio of UGT2B4, in which (R)-glucuronidation was much more easily inhibited by (S)-carvedilol than was (S)-glucuronidation by (R)-carvedilol. Meanwhile, HIM preferred metabolizing (R)-carvedilol, and this tendency was not different between the kinds of substrate form.     

Stereospecific determination of citalopram and desmethylcitalopram by capillary electrophoresis and liquid-phase microextraction

A chiral capillary electrophoresis (CE) system allowing simultaneous enantiomer determination of citalopram (CIT) and its pharmacologically active metabolite desmethylcitalopram (DCIT) was developed. Excellent chiral separation was obtained using 1% sulfated-beta-cyclodextrin (S-beta-CD) as chiral selector in combination with 12% ACN in 25 mM phosphate pH 2.5. Samples were prepared by liquid-phase microextraction (LPME) based on a rodlike porous polypropylene hollow fibre. CIT and DCIT were extracted from 1 ml plasma made alkaline with NaOH, into dodecyl acetate impregnated in the pores of a hollow fibre, and into 20 mM phosphate pH 2.75, inside the hollow fibre. The acceptor solution was directly compatible with the CE system. Efficient sample clean-up was seen, and the recoveries were 46 and 29% for the enantiomers of CIT and DCIT, respectively, corresponding to 31 and 19 times enrichment. The limit of quantification (S/N=10) was <11.2 ng/ml, intra-day precision was <12.8% RSD, and inter-day precision was <14.5% RSD, for all enantiomers. The validated method was successfully applied to simultaneous determination of enantiomer concentrations of CIT and DCIT in plasma samples from nine patients treated with racemic citalopram. The results confirm LPME-CE as a suitable and promising tool for enantiomeric determination of chiral drugs and metabolites in biological matrices.     

Determination of MDMA and its metabolites in blood and urine by gas chromatography-mass spectrometry and analysis of enantiomers by capillary electrophoresis

A gas chromatography-mass spectrometry (GC-MS) method was used for the simultaneous quantitation of 3,4-methylenedioxymethamphetamine (MDMA) and the 3,4-methylenedioxyamphetamine (MDA), 4-hydroxy-3-methoxymethamphetamine (HMMA), and 4-hydroxy-3-methoxyamphetamine (HMA) metabolites in plasma and urine samples after the administration of 100 mg MDMA to healthy volunteers. Samples were hydrolyzed prior to a solid-phase extraction with Bond Elut Certify columns. Analytes were eluted with ethyl acetate (2% ammonium hydroxide) and analyzed as their trifluoroacyl derivatives. Linear calibration curves were obtained at plasma and urine concentration ranges of 25-400 ng/mL and 250-2000 ng/mL for MDMA and HMMA, and of 2.5-40 ng/mL and 100-1000 ng/mL for MDA and HMA. Following the same urine preparation procedure but without the derivatization step, a capillary electrophoresis (CE) method for enantiomerical resolution of compounds was developed using (2-hydroxy)propyl-beta-cyclodextrin at two different concentrations (10 and 50mM in 50mM H3PO4, pH 2.5) as chiral selector. Calibration curves for the CE method were prepared with the corresponding racemic mixture and were linear between 125 and 2000 ng/mL, 50 and 1000 ng/mL, and 125 and 1500 ng/mL for each enantiomer of MDMA, MDA, and HMMA, respectively. Stereoselective disposition of MDMA and MDA was confirmed. HMMA disposition seems to be in apparent contradiction with MDMA findings as the enantiomer ratio is close to 1 and constant over the time.     

Chiral purity test of bevantolol by capillaryelectrophoresis and high performance liquid chromatography

Two methods for the chiral purity determination of bevantolol were developed, namely capillary electrophoresis (CE) using carboxymethyl-beta-cyclodextrin (CM-beta-CD) as a chiral selector and high-performance liquid chromatography (HPLC) using a chiral stationary phase. In the HPLC method, the separation of bevantolol enantiomers was performed on a Chiralpak AD-H column by isocratic elution with n-hexane-ethanol-diethylamine (10:90:0.1, v/v/v) as mobile phase. In the CE method, bevantolol enantiomers were separated on an uncoated fused silica capillary with 50 mM amonium phosphate dibasic adjusted to a pH 6.5 with phosphoric acid containing 15 mM CM-beta-CD as running buffer. Validation data such as linearity, recovery, detection limit, and precision of the two methods are presented. The detection limits of S-(-)-bevantolol were 0.1% and 0.05% for CE and HPLC method, respectively and R-(+)-bevantolol were 0.15% and 0.05% for CE and HPLC method, respectively. There was generally good agreement between the HPLC and CE results.     

正交试验优选拆分5种碱性药物的毛细管电泳法

目的以羧甲基-β-环糊精(carboxymethyl-β-cyclodextrin,CM-β-CD)为手性选择剂,用毛细管电泳法(capillary electrophoresis,CE)对5种碱性药物苯磺酸氨氯地平(amlodipine besilate)、二氧丙嗪(dioxopromethazine)、硫酸特布他林(terbutaline sulfate)、氢溴酸后马托品(homatropinehydrobromide)和盐酸美普他酚(meptazinol hydrochloride)进行对映体分离研究。方法采用正交试验设计的方法考察3个水平数背景电解质溶液的pH值、CM-β-CD浓度、缓冲盐浓度对对映体分离的影响,优化了分离条件。结果在最优分离条件下,苯磺酸氨氯地平、二氧丙嗪、硫酸特布他林、氢溴酸后马托品、盐酸美普他酚对映体达到良好分离,分离度分别为12.6、4.4、6.0、5.7、3.5。结论 CM-β-CD对5种碱性药物均具有较好的对映体选择性。     

Stereoselective metabolism of carvedilol in the rat. Use of enantiomerically radiolabeled pseudoracemates.

14C-Labeled R(+)- and S(-)-carvedilol enantiomers were prepared by direct resolution of 14C-labeled racemic carvedilol on a chiral HPLC column. Two enantiomerically radiolabeled carvedilol pseudoracemates, 14C-labeled R(+)/unlabeled S(-)-carvedilol and 14C-labeled S(-)/unlabeled R(+)-carvedilol, were reconstituted and administered orally and iv to separate groups of bile duct-cannulated rats to determine the biliary excretion of carvedilol enantiomers and the stereochemical composition of metabolites excreted into the bile. The respective biliary excretions of the radioactivity derived from the radiolabeled R(+)- and S(-)-enantiomers accounted for 41.4 +/- 0.9 and 41.5 +/- 1.9% of the oral racemic dose, and 43.7 +/- 2.4 and 40.0 +/- 0.9% of the iv dose. Oral administration of these pseudoracemates produced no enantiomeric difference in the biliary excretion of the radioactivity derived from the enantiomers, whereas iv administration did result in an enantiomeric difference: the biliary excretion rate of the radioactivity derived from R(+)-enantiomer was higher than that from S(-)-enantiomer. After administration by the two routes, two carbazole ring-hydroxylated glucuronides, 1-hydroxycarvedilol O-glucuronide (1-OHCG) and 8-hydroxycarvedilol O-glucuronide (8-OHCG), were detected as the major metabolites in the bile. The S/R enantiomer ratios of 1-OHCG were 0.59 for oral dosing and 0.43 for iv dosing, suggesting that the formation of 1-OHCG is selective for R(+)-enantiomer, while the S/R ratios of 8-OHCG showed values of 3.29 and 2.63 for oral and iv administrations, respectively, favoring S(-)-enantiomer. Since corresponding hydroxylated metabolites are rapidly biotransformed to glucuronides that are excreted predominantly in the bile, the stereoselectivity of these glucuronides presumably reflects that of carbazole ring hydroxylation.     

Assay and disposition of carvedilol enantiomers in humans and monkeys: evidence of stereoselective presystemic metabolism

Carvedilol is a new beta-blocking agent with vasodilating activities, which is a racemic mixture of R(+)- and S(-)-enantiomers. Since the two enantiomers differ in pharmacological properties, it is necessary to individually measure their plasma concentrations in order to evaluate the pharmacological effects of racemic carvedilol after oral administration. In this study, a sensitive, stereospecific high-performance liquid chromatographic assay was used to determine the plasma concentration of each enantiomer. The assay involves the diastereomeric derivatization of racemic carvedilol with 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl isothiocyanate as a chiral reagent. After oral administration of racemic carvedilol to humans, the mean Cmax and AUC infinity values for R(+)-enantiomer were 2.6 and 2.8 times greater, respectively, than those for the more active S(-)-enantiomer. Similarly, in monkeys, the respective R:S enantiomer ratios for Cmax and AUC infinity were 1.5 and 1.2. The difference in AUCoral between these enantiomers is ascribed to the greater intrinsic clearance of S(-)-enantiomer than that of the R(+)-enantiomer in the liver, and to a lower plasma protein binding of the S(-)-enantiomer.     

Chiral separation and quantitation of pentazocine enantiomers in pharmaceuticals by capillary zone electrophoresis using maltodextrins

The chiral separation of pentazocine was achieved by capillary electrophoresis using oligosaccharides. Enantiomers were separated on 100 mM Tris/H3PO4 buffer (pH 2.5) with 5% maltodextrin as a chiral selector, and migration behavior was monitored at 200 nm. Under these conditions, (-)- and (+)-pentazocine and dextromethorphan (internal standard) migrated within 9 min, and the resolution of pentazocine enantiomers was 2.54. Linear calibration curves were obtained in the range 5-50 microg/ml(-1) for each enantiomer. The detection limit of pentazocine enantiomers was 29 pg, and the recoveries of(-)- and (+)-pentazocine were 98.9 (R.S.D., 3.4%) and 101.4% (R.S.D., 4.3%) with 10 microg/ml(-1), respectively.     

Pharmacokinetics of acebutolol enantiomers in humans.

The chiral beta-blocker acebutolol (AC) is marketed as a racemic mixture. Both AC and its major metabolite, diacetotol (DC), are chiral, the S-enantiomer possessing beta-blocking activity. The pharmacokinetics of AC and DC enantiomers was determined in 12 healthy subjects following oral administration of 200 mg of AC. Plasma and urine were collected over a 24-hr period and both AC and DC enantiomers were measured utilizing a stereospecific HPLC assay. Concentrations of S-AC were predominant in both plasma and urine [AUC S:R, 1.20 +/- 0.1; cumulative urinary excretion (sigma Xu) S:R, 1.17 +/- 0.05), which corresponded to a significantly greater oral clearance of R-AC (106 +/- 30 L/h) than S-AC (87 +/- 22 L/h). The Cmax of R-DC was significantly greater than for S-DC (S/R 0.7 +/- 0.1). The half-life (t1/2) of R-DC (6.4 +/- 1.6 h) was significantly shorter than that of S-DC (8.8 +/- 2.4 h). The observed AUC values for R- and S-DC were not significantly different. Renal clearance of R-DC (70 +/- 34 mL/min) was significantly greater than that of S-DC (53 +/- 29 mL/min). The data suggest that the first-pass metabolism of R-AC to R-DC is stereoselective. This metabolism, coupled with the stereoselective renal excretion of R-DC is likely a major contributor to the observed stereoselective disposition of AC and its major metabolite in humans.     

Stereoselective analysis of carvedilol in human plasma using HPLC/MS/MS after chiral derivatization

A relatively high-throughput high-performance liquid chromatography/tandem mass spectrometry (HPLC-MS/MS) method using a chiral derivatization reagent was developed for the quantitative determination of carvedilol enantiomers in human plasma. S-carvedilol and R-carvedilol are extracted from human plasma by protein precipitation using acetonitrile containing racemic [(2)H(5)]-carvedilol as an internal standard. Extracts are then derivatized with 2,3,4,6-tetra-O-acetyl-beta-glucopyranosyl isothiocyanate (GITC) and analysed using HPLC-MS/MS with a TurboIonspray (TIS) interface and selected reaction monitoring. Using 150microL of plasma, the method was validated over a concentration range of 0.2-200ng/mL. The maximum within-run precision observed in a three run quality control was 8.2% for S-carvedilol and 6.7% for R-carvedilol, respectively. The maximum percentage bias observed at all quality control sample concentrations was 9.4% for S-carvedilol and 11.6% for R-carvedilol, respectively. The HPLC-MS/MS method was also compared with a previously developed high-performance LC/fluorescence method by analysing 25 samples containing racemic carvedilol. Based on results obtained, these two methods were found to be equivalent. However, compared with LC/fluorescence method, HPLC-MS/MS method is more sensitive, uses less plasma, and also employs a less time-consuming sample preparation process.     

Chiral separation of ketoprofen on an achiral C8 column by HPLC using norvancomycin as chiral mobile phase additives

A high-performance liquid chromatographic method for chiral separation of ketoprofen racemate was developed. (R)- and (S)-ketoprofen enantiomers were separated on a Hypersil BDS C8 column (150 mm x 4.6 mm i.d., 5 microm) at 25 degrees C, using acetonitrile-triethylamine acetate (TEAA) buffer (pH 5.2, 20 mM) (35:65, v/v) containing 2.0 mM norvancomycin as the mobile phase. Effects of norvancomycin concentration, content of acetonitrile and TEAA buffer pH on the enantioseparation were investigated. The method was validated for linearity, repeatability, limits of detection (LOD) and limits of quantification (LOQ). Calibration curves (r2 = 0.999) were constructed in the range of 2.01-200.8 microg ml(-1) for (S)-ketoprofen and 2.04-152.4 microg ml(-1) for (R)-ketoprofen, respectively. Repeatability (n = 5) showed less than 2% relative standard deviation (R.S.D.). LOD and LOQ for the two enantiomers were found to be 0.20 and 0.78 ng for (S)-ketoprofen, 0.20 and 0.86 ng for (R)-ketoprofen, respectively. Norvancomycin and vancomycin as chiral mobile phase additives (CMPAs) in the chiral separation showed similar abilities of enantioseparation. However, to obtain the optimum enantioseparation, a lower concentration of norvancomycin than that of vancomycin is required.     

Stereoselective effect of amiodarone on the pharmacokinetics of racemic carvedilol

We investigated whether there was a stereoselective effect of amiodarone on the pharmacokinetics of carvedilol. Among a series of 106 inpatients with heart failure, 52 received carvedilol monotherapy (carvedilol group) and 54 received carvedilol plus amiodarone (carvedilol+amiodarone group). The serum carvedilol concentration administered/dose ratio was compared between the two groups based on HPLC measurement of the serum levels of carvedilol, amiodarone, and desethylamiodarone. In 6 patients from the carvedilol group, serum carvedilol levels were compared before and after coadministration of amiodarone. There was no significant between-group difference of the serum concentration to dose (C/D ratio) for the R-enantiomer carvedilol, however, the C/D ratio for the S-enantiomer and the serum S-carvedilol to R-carvedilol (S/R) ratio were both significantly lower in the carvedilol group than in the carvedilol+amiodarone group(47.8+/-56.7 versus 95.3+/-105 ng/mg/kg, P=0.0048 and 0.460+/-0.207 versus 0.879+/-0.377 ng/mg/kg, P<0.001), respectively. Furthermore, the mean S-carvedilol concentration over 14 days of coadministration with amiodarone was higher than that before coadministration (6.54+/-1.73 ng/mL versus 3.03+/-0.670 ng/mL, P<0.001). These results suggest that metabolism of S-carvedilol was markedly inhibited by coadministration of amiodarone.     

Enantiomeric purity determination of tamsulosin by capillary electrophoresis using cyclodextrins and a polyacrylamide-coated capillary

The chiral separation of racemic tamsulosin hydrochloride (TH) was carried out using cyclodextrin (CD)-mediated capillary electrophoresis (CE) with DAD at 200 nm. The best separation of enantiomers of the studied compound was achieved at 20 kV with 30 cm x 50 microm I.D. polyacrylamide (PAA)-coated fused-silica capillary (effective length 20 cm) and running buffer with sulfated-beta-CD (S-beta-CD) as chiral selector. Other selected native or derivatized CDs were also tested: beta-CD (5, 15 mmol l(-1)), carboxymethyl-beta-CD (5, 30 mmol l(-1)), dimethyl-beta-CD (15 mmol l(-1)) and hydroxypropyl-beta-CD (5, 30 mmol l(-1)). Several parameters such as capillary pretreatment, buffer type and concentration, pH of background electrolyte, methanol content, separation temperature and voltage, were optimized. The excellent baseline separation of chiral TH was successfully achieved within 12 min using 100 mmol l(-1) phosphate buffer with pH 2.5 containing 1.7 mmol l(-1) S-beta-CD. Rectilinear calibration range was 50.0-500.0 mumol l(-1) of each enantiomer (r = 0.9993-0.9996). The method was applied to the assay of R-TH in Omnic, capsules (nominal content 0.4 mg per capsule) with R.S.D. 2.75% (n = 6), recovery 99.3-101.7% and it was suitable for the chiral purity control of the active enantiomer in the pharmaceutical.