Sotalol Enantiomers Research Articles

Enantioselective liquid chromatographic-electrospray mass spectrometric assay of β-adrenergic blockers: application to a pharmacokinetic study of sotalol in human plasma

An enantioselective high performance liquid chromatographic-electrospray ionization mass spectrometric (HPLC-ESI-MS) method for the direct determination of several β-adrenergic blockers was developed and validated. The method is based on the direct separation of the enantiomers of drugs on a laboratory-made chiral stationary phase (CSP) containing covalently bonded teicoplanin (TE) as chiral selector. Detection of the effluent was performed by electrospray ionization mass spectrometry, run in the selected-ion recording (SIR) mode. The method was applied to the pharmacokinetic monitoring of sotalol (STL) in the plasma of five young healthy volunteers, dosed with racemic drug. The limits of quantitation (LOQ) reached 4 ng/ml for both sotalol enantiomers. Such a method, fully validated, offers a novel, fast and very efficient tool for the direct determination of sotalol enantiomers in human plasma, and can be generally applied to the β-adrenergic blockers stereoselective pharmacokinetics.

Enantioselective determination of ( R)- and ( S)-sotalol in human plasma by on-line coupling of a restricted-access material precolumn to a cellobiohydrolase I-based chiral stationary phase

A liquid chromatographic column-switching method for the enantioselective determination of ( RS)-sotalol in plasma was developed and validated. The method is based on the on-line coupling of a precolumn filled with the restricted access material LiChrospher ADS to a cellobiohydrolase I-based chiral stationary phase (CSP). The plasma samples were injected onto the precolumn using a mobile phase containing 1% methanol in 10 m M phosphate buffer at pH 7.4 for 10 min for the removal of matrix components. The analytes were transferred to the CSP for their enantiomeric separation by backflushing the precolumn with 15% 2-propanol in 10 m M phosphate buffer (pH 7.0) including 0.05 m M EDTA. The quantitative determination of the sotalol enantiomers was possible upon addition of the internal standard ( S)-atenolol. The method was validated showing a good linearity in the concentration range from 25 to 1000 μg l −1 for each enantiomer. The average values of the intra- and inter-day variability were 1.17% and 3.42%, respectively, for ( R)-sotalol and 1.24% and 1.99%, respectively, for ( S)-sotalol. The applicability of the method to real world samples has been proven by means of two pharmacokinetic studies. They revealed that the pharmacokinetic properties of the sotalol enantiomers do not differ significantly neither for healthy young volunteers after single dose application nor for elder patients in the steady state.

Drug-disease interactions: reduced beta-adrenergic and potassium channel antagonist activities of sotalol in the presence of acute and chronic inflammatory conditions in the rat.

Inflammation may influence response to pharmacotherapy. We investigated the effect of inflammation on response to sotalol, a beta-adrenergic receptor and potassium channel antagonist. Racemic sotalol (40 mg kg(-1)) was administered to healthy, acutely (interferonalpha 2a-induced) and chronically (Mycobacterium butyricum-induced adjuvant arthritis) inflamed male Sprague-Dawley rats (n=4 - 6/group). Another group of interferon-treated rats received 3 mg kg(-1) of anti-TNF antibody infliximab. Electrocardiogram (ECG) recorded and plasma sotalol concentration monitored for 6 h. The study was repeated in acutely inflamed rats following administration of stereochemically pure individual sotalol enantiomers [40 mg kg(-1) S (potassium channel blocker) or 20 mg kg(-1) R (beta-adrenergic/potassium channel blocker)]. Chronic arthritis was readily evident. Acute arthritis was associated with elevated segmented neutrophils and increased plasma nitrite and tumour necrosis factor (TNF) concentrations. Sotalol affected ECG in all rats. In both inflamed groups, however, response to sotalol in prolongation of QT interval (potassium channel sensitivity) was reduced. The effect of PR interval (beta-adrenergic activity) was also reduced following administration of the racemate and R-enantiomer. No significant differences in pharmacokinetics were observed between control and inflamed rats. Infliximab reduced nitrite and TNF concentrations and reversed the effect of acute inflammation on both PR and QT intervals. The reduced electrocardiographic responses to sotalol is likely due to the influence of inflammation on the action of the drug on both beta-adrenergic and potassium channel receptors secondary to over-expression of pro-inflammatory cytokines and/or nitric oxide. Our observation may have therapeutic consequences in all conditions where inflammatory mediators are increased.

Direct liquid chromatographic enantioseparation of sotalol and other β-blockers using an α1-acid glycoprotein-based chiral stationary phase

The behaviour of an α 1-acid glycoprotein-based chiral stationary phase (Chiral AGP) towards changes in pH and organic modifier in the mobile phase was investigated in order to deduce suitable conditions for the liquid chromatographic enantioseparation of a series of β-adrenoreceptor blocking drugs. The effects of the pH of the mobile phase on retention, selectivity and resolution were studied. Methanol was the only non-ionic modifier tested in the mobile phase while different aliphatic carboxylic acids (C 4 to C 8) and alkanesulfonic acids (C 6 to C 8) were used as ionic modifiers. The influence of the nature and concentration of these modifiers on retention and enantioselectivity was investigated. Under these conditions, enantiomeric separations could be obtained for more than 70% of the β-blocking agents examined. The use of heptanoic acid as an ionic additive in the mobile phase has permitted the resolution of sotalol enantiomers. An enantioselective assay for sotalol was then developed and validated.

Renal, biliary and intestinal clearance of sotalol enantiomers in rat model: evidence of intestinal exsorption.

Biliary clearance (Clb) of sotalol (STL) enantiomers was assessed in anaesthetized Sprague-Dawley rats (419 +/- 9 g, mean +/- SEM, n = 4) following administration of a 10 mg kg-1 i.v. dose of the racemate. Clb for S- and R-STL (0.0675 +/- 0.0090 and 0.0662 +/- 0.0089 mL min-1 kg-1, respectively) represented approximately 0.3% of systemic clearance (Cls) values for S- and R-STL (20.4 +/- 2.2 and 20.7 +/- 2.0 mL min-1 kg-1, respectively). Bile:plasma concentration ratios at 1, 2, and 3 h post-dose were approximately 1.4, 1.3, and 1.2 for both STL enantiomers. Renal clearance (Clr) and intestinal clearance (Cli) of STL enantiomers were assessed in conscious Sprague-Dawley rats (325 g, n = 4) following administration of a 10 mg kg-1 i.v. dose of the racemate. STL enantiomers were predominantly eliminated intact in the urine: Clr for S- and R-STL (26.3 +/- 3.2 and 28.7 +/- 4.2 mL min-1 kg-1 respectively) accounted for approximately 96% of Cls for S- and R-STL (27.5 +/- 3.3 and 29.9 +/- 4.2 mL min-1 kg-1, respectively). Approximately 4% of the dose was recovered in the faeces, corresponding to Cli values of 1.16 +/- 0.17 and 1.26 +/- 0.19 mL min-1 kg-1 for S- and R-STL, respectively. Total recovery of the administered dose in urine and faeces was 99.7 +/- 0.2 and 99.8 +/- 0.5% for S- and R-STL, respectively. It is concluded from these results in the rat model that (i) STL enantiomers are predominantly eliminated intact in urine; (ii) STL enantiomers are excreted intact in bile, and to a much larger extent in the faeces, thus suggesting the presence of intestinal exsorption of STL; (iii) STL does not appear to be metabolized; and (iv) Cls, Clr, Clb, and Cli are negligibly stereoselective.

Enantioselective determination of sotalol enantiomers in biological fluids using high-performance liquid chromatography

A simple and sensitive high-performance liquid chromatograhic (HPLC) method for the determination of (+)-( S)-sotalol and (−)-( R)-sotalol in biological fluids was established. Following extraction with isopropyl alcohol from biological samples on a Sep-Pak C 18 cartridge, the eluent was derivatized with 2,3,4,6-tetra-O-acetyl-β- d-glucopyranosol isothiocyanate (GITC). The diastereoisomeric derivatives are resolved by HPLC with UV detection at 225 nm. Calibration was linear from 0.022 to 4.41 μg/ml in human plasma and from 0.22 to 88.2 μg/ml in human urine for both (+)-( S)- and (−)-( R)-sotalol. The lower limit of determination was 0.022 μg/ml for plasma and 0.22 μg/ml for urine. The within-day and day-to-day coefficients of variation were less than 7.5% for each enantiomer at 0.09 and 1.8 μg/ml in plasma and at 0.44 and 4.4 μg/ml in urine. The method is also applicable to other biological specimens such as rat, mouse and rabbit plasma.

Protein binding of sotalol enantiomers in young and elderly human and rat serum using ultrafiltration

The protein binding of sotalol (STL) enantiomers was evaluated using an ultrafiltration technique with serum from young (32 +/- 2 years, n = 5) and elderly (73 +/- 6 years, n = 5) male and female humans, and young (8 weeks, n = 4) and elderly (60 weeks, n = 3) male Sprague-Dawley rats. Serum samples were collected and immediately frozen at -20 degrees C. Within 1 week, the serum samples were thawed at room temperature, and adjusted to pH 7.4 using 0.05 M phosphate buffer, pH 5.0. Aliquots were spiked with 250 ng mL-1 and 500 ng mL-1 of each STL enantiomer, placed in ultrafiltration sets (Microsep, 30K molecular weight cut-off), capped, equilibrated to 37 degrees C, and centrifuged at 1850g for 1.5 h at 37 degrees C. Aliquots of ultrafiltrate and unspun serum were analysed for STL enantiomer concentration using a stereospecific HPLC assay. In all groups, bound fraction was less than 7% for both STL enantiomers. There were no significant differences in bound fraction between groups, or between enantiomers. Adsorption of STL enantiomers to the ultrafiltration device and membrane, evaporative loss of serum samples during centrifugation, and protein concentration in each ultrafiltrate sample were all negligible. It is concluded that the binding of STL in human and rat serum at therapeutic concentrations and physiological temperature and pH is negligible and non-stereoselective.

Pharmacokinetics of Sotalol Enantiomers after Single and Repeated Oral Administration of Sotalol Hydrochloride to Rats.

塩酸 sotalol をラットに 10，100，300mg/kg 単回投与および 30mg/kg/day を1日1回7日間反復投与したときの，光学異性体の体内動態を光学分割定量法を用いて試験した．また，これらの試験を2種の異なる採血方法を用いて比較検討した．1)塩酸 sotalol をラットに単回経口投与したとき，d-および l-sotalol はともに線形性の体内動態を示した．2)反復投与における初回投与後と7回投与後の d- および l-sotalol の体内動態に変化は認められず，蓄積性のないことも確認された．3)単回および反復投与において，d- および l-sotalol の体内動態に差は認められなかった．4)単回投与したときの48時間までの尿中排泄率は d-体，l-体いずれも平均約70%であり，その大部分は24時間以内に排泄された．5)Sotalol のラットにおける体内動態を，(1)同一動物から経時的に採血する方法と，(2)採血点ごとに異なる動物を使用し，多量の血液を採取する方法の2種類の試験方法で検討した結果，両試験法で得られた結果に顕著な差はみられなかった．6)ヒト，イヌおよびラットの in vitro 血清蛋白結合率を測定した結果，d- 体および l-体の蛋白結合率は，いずれも平均約 9% と低く，光学異性体間に差はなく，種差および濃度による変化も認められなかった．

Stereoselective disposition of (+/‐)‐sotalol at steady‐state conditions.

The objective of this study was to assess, under steady-state conditions, the stereoselective disposition of (+/-)-sotalol in man. In all patients studied (n = 7) values of oral clearance (137 +/- 51 ml min-1), renal clearance (96 +/- 42 ml min-1) and nonrenal clearance (41 +/- 25 ml min-1) of (-)-sotalol were greater than those for (+)-sotalol (123 +/- 45 ml min-1, 89 +/- 39 ml min-1 and 34 +/- 23 ml min-1, respectively; P < 0.05, Student's paired t-test). Binding to plasma proteins was greater for (+)-sotalol (38 +/- 9% vs 35 +/- 9% for the (-)-enantiomer; P < 0.05) such that unbound oral clearance (+)/(-) ratio (0.95 +/- 0.06) and unbound renal clearance (+)/(-) ratio (0.97 +/- 0.06) were not stereoselective. In contrast, estimated unbound nonrenal clearance, which represents approximately 25% of the total unbound clearance of the drug, was greater for the (-)-enantiomer (64 +/- 42 ml min-1) compared with (+)-sotalol (57 +/- 42 ml min-1; P < 0.05). The difference in the pharmacokinetics of sotalol enantiomers is mainly related to stereoselectivity in plasma protein binding.

Stereoselective high-performance liquid chromatographic assay for the determination of sotalol enantiomers in biological fluids

A high-performance liquid chromatographic (HPLC) assay for determination of sotalol enantiomers in biological fluids was developed to assess the stereoselective disposition of the drug in man. Following extraction at pH 9.0 with a mixture of chloroform-isopropanol (3:1, v/v), the organic phase was evaporated to dryness and the residue derivatized with (−)-menthyl chloroformate. Diastereoisomeric derivatives were resolved by HPLC (C 8 column) with fluorescence detection (λ ex = 235 nm and λ em = 300 nm). Retention times of l- and d-sotalol derivatives were 13 and 15 min while that of the internal standard, S-(−)-atenolol, was 12.3 min. The detection limit of each enantiomer was 12.5 ng/ml using 1 ml of plasma or urine. Intra-day and inter-day coefficients of variation were less than 10% for each enantiomer in the range 0.125–2.5 μg/ml in plasma and 0.25–2.5 μg/ml in urine.

Pharmacokinetics of Sotalol Enantiomers in Humans

The chiral beta-blocker, sotalol (STL), is marketed as a racemic mixture. Although both STL enantiomers have equal Class III antiarrhythmic activity, beta-blocking activity has been ascribed mainly to the R-enantiomer. The pharmacokinetics of STL enantiomers were studied in young (mean age 32 +/- 3 years), healthy male volunteers after oral administration of 160 mg. Subsequent plasma and urine samples were collected over 24 hours, and STL enantiomer concentrations were determined using a stereospecific high-performance liquid chromatography assay. There were no significant differences between pharmacokinetic parameters of enantiomers. The area under the time-concentration curves (mean +/- standard deviation [SD]) were 6.95 +/- 0.85 and 6.76 +/- 1.2 (mg/L)hour for S- and R-STL, respectively. Maximal plasma concentrations of S- and R-STL were 615 +/- 167 and 619 +/- 164 ng/mL, respectively, which were obtained on average, 3.13 +/- 0.60 hours after dosing. The mean residence time (mean +/- SD) was 13.2 +/- 1.2 and 12.9 +/- 1.8 hours for S- and R-STL, respectively. Respective renal clearance values for S- and R-STL were 8.98 +/- 1.5 and 9.46 +/- 2.3 L/hour, and were approximately 1.5 times greater than creatinine clearance. Renal clearance constituted approximately 76% of the oral clearance. Although stereoselective disposition of STL was absent after racemate administration, these results should not be extrapolated to patients with significantly altered physiology, or to the pharmacokinetics of S-STL after administration of pure-S-STL.

Stereospecific high-performance liquid chromatographic assay of sotalol in plasma.

A convenient high-performance liquid chromatographic (HPLC) assay was developed for determination of sotalol (STL) enantiomers in plasma. Following addition of the internal standard (IS; racemic atenolol), enantiomers of STL and IS were extracted using ethyl acetate. After evaporation of the organic layer, samples were derivatized with a solution of S-(+)-1-(1-naphthyl)ethyl isocyanate (NEIC). The resulting diastereomers were chromatographed with normal-phase HPLC with chloroform:hexane:methanol [65:33:2 (v/v)] as the mobile phase at a flow rate of 2 ml/min. The fluorescence detection wavelength was set at 220 nm for excitation with no emission filter. The suitability of the assay for pharmacokinetic studies was determined by measuring STL enantiomers in the plasma of a healthy subject after administration of a single 160-mg oral, racemic dose of STL.