High-throughput LC-MS/MS method with 96-well plate precipitation for the determination of arotinolol and amlodipine in a small volume of rat plasma: Application to a pharmacokinetic interaction study.

A rapid, sensitive, and selective liquid chromatography with tandem mass spectrometry method was developed and fully validated for the simultaneous quantification of arotinolol and amlodipine in rat plasma. Two internal standards were introduced with metoprolol as the internal standard of arotinolol and (S)-amlodipine-d4 as the internal standard of amlodipine. The analytes were isolated from 50.0 µL plasma samples by a simple protein precipitation using acetonitrile. The chromatographic separation was achieved in 5 min on a C18 column. The mobile phase consisted of phase A 5% methanol and phase B 95% methanol (both containing 0.5% formic acid and 5 mM ammonium acetate) and was delivered in gradient elution at 0.300 mL/min. Quantification was performed in multiple reaction monitoring mode with the transition m/z 372.1 â†’ 316.1 for arotinolol, m/z 268.2 â†’ 116.2 for metoprolol, m/z 409.1 â†’ 238.1 for amlodipine and m/z 413.1 â†’ 238.1 for (S)-amlodipine-d4. Linearity was obtained over the range of 0.200-40.0 ng/mL for arotinolol (r2  = 0.9988) and 0.500-100 ng/mL for amlodipine (r2  = 0.9985) in rat plasma. The validated data have met the acceptance criteria in FDA guideline. This method was successfully applied to a pharmacokinetic interaction study in rats, and the results indicated that there was no significant drug-drug interaction between arotinolol and amlodipine.

A rapid LC-MS/MS method for simultaneous determination of quetiapine and duloxetine in rat plasma and its application to pharmacokinetic interaction study.

Combinations of new antidepressants like duloxetine and second-generation antipsychotics like quetiapine are used in clinical treatment of major depressive disorder, as well as in forensic toxicology scenarios. The drug-drug interaction (DDI) between quetiapine and duloxetine is worthy of attention to avoid unnecessary adverse effects. However, no pharmacokinetic DDI studies of quetiapine and duloxetine have been reported. In the present study, a rapid and sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed for simultaneous determination of quetiapine and duloxetine in rat plasma. A one-step protein precipitation with acetonitrile was applied for sample preparation. The analytes were eluted on an Eclipse XDB-C18 column using the mixture of acetonitrile and 2 mM ammonium formate containing 0.1% formic acid at a gradient elution within 6.0 min. Quantification was performed in multiple-reaction-monitoring mode with the ion transitions m/z 384.4 â†’ 253.2 for quetiapine, m/z 298.1 â†’ 154.1 for duloxetine and m/z 376.2 â†’ 165.2 for IS (haloperidol), respectively. Good linearity was obtained in the range of 0.50-100 ng/mL for quetiapine (r2 = 0.9972) and 1.00-200 ng/mL for duloxetine (r2 = 0.9982) using 50 µL of rat plasma, respectively. The method was fully validated with accuracy, precision, matrix effects, recovery and stability. The validated data have met the acceptance criteria in FDA guideline. The method was applied to a pharmacokinetic interaction study and the results indicated that quetiapine had significant effect on the enhanced plasma exposure of duloxetine in rats under combination use. This study could be readily applied in therapeutic drug monitoring of major depressive disorder patients receiving such drug combinations.

[Chiral separation of four ß-blocker enantiomers using high performance liquid chromatography-tandem mass spectrometry based on amylase derivative chiral stationary phases and investigation on their separation mechanism].

A high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method based on amylose derivatives as chiral stationary phases (CSPs) for the chiral separation of four ß-blocker enantiomers (propanolol, metoprolol, arotinolol and carvedilol) was established. The effects of different CSPs, volume fractions of mobile phase modifiers and mobile phase additives, column temperatures and flow rates on the chiral separation of the four ß-blocker enantiomers were evaluated. Baseline separation of the four ß-blockers enantiomers was obtained on a Chiralpak AD-H chiral column using the mobile phase of n-hexane-ethanol-diethylamine (20:80:0.03, v/v/v) at a flow rate of 0.550 mL/min and a column temperature of 40℃. The resolutions of the enantiomers for propanolol, metoprolol, arotinolol and carvedilol were 1.37, 1.80, 2.09 and 4.70, respectively. The separation mechanism of the four ß-blocker enantiomers was investigated by thermodynamic analysis and enantiomeric structure analysis. The chiral separation was all enthalpy controlled, and the cave structure of the chiral stationary phase played an important role on the separation. The method provides reference for further studies of the ß-blocker enantiomers.

Ultrasound-assisted low-density solvent dispersive liquid-liquid microextraction for the simultaneous determination of 12 new antidepressants and 2 antipsychotics in whole blood by gas chromatography-mass spectrometry.

Antidepressant drugs are widely used in the treatment of different psychiatric disorders, as well as in conjunction with antipsychotics for the treatment of major depressive disorder. In this study, a simple and rapid ultrasound-assisted low-density solvent dispersive liquid-liquid microextraction (UA-LDS-DLLME) method was developed for the simultaneous determination of 12 new antidepressants (norfluoxetine, fluoxetine, fluvoxamine, agomelatine, mirtazapine, moclobemide, melitracen, N-desmethylmirtazapine, maprotiline, sertraline, citalopram, paroxetine) and 2 antipsychotics (clozapine and haloperidol) in human whole blood by gas chromatography-mass spectrometry (GC-MS). Different parameters affecting the UA-LDS-DLLME were optimized and the optimal conditions were as follows: 100µL of toluene as extraction solvent, extraction pH 12 and 3min of ultrasound stirring. Good linearity (R2≥0.991) was obtained at the concentration range of 15-1500ng/mL for norfluoxetine, fluoxetine, fluvoxamine, melitracen, maprotiline and citalopram, and 5-500ng/mL for agomelatine, mirtazapine, moclobemide, N-desmethylmirtazapine, sertraline, paroxetine, clozapine and haloperidol. The intra-day and inter-day precision were all less than 10%, and accuracy of intra-day and inter-day were in the range of -12.7% to 7.9% and -13.9 to 11.8%, respectively. The extraction recoveries of most analytes were more than 60%. The UA-LDS-DLLME/GC-MS method was demonstrated with acceptable precision, accuracy and good specificity for the simultaneous determination of 12 antidepressants and 2 antipsychotics, and has been successfully applied in a real case.

Enantiospecific determination of arotinolol in rat plasma by LC-MS/MS: application to a stereoselective pharmacokinetic study.

A highly sensitive and selective liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and fully validated for quantification of arotinolol enantiomers in rat plasma using haloperidol as the internal standard. After solid phase extraction of 50.0 µL rat plasma in 96 well plate, a baseline resolution of arotinolol enantiomers was achieved on a CHIRALPAK AD-H column using the mobile phase of n-hexane and ethanol in 0.02% diethylamine (20:80, v/v) at a flow rate of 0.550 mL/min within 11.0 min. Acquisition of mass spectrometric data was performed on a triple-quadrupole mass spectrometer in multiple-reaction-monitoring (MRM) mode with an ESI source using the transition m/z 372.1 → 316.1 for (±)-arotinolol and m/z 376.1 → 165.1 for haloperidol. The calibration curves of both enantiomers were linear over the range of 1.00-200.0 ng/mL (r(2)>0.992) and the lower limit of quantification was 1.00 ng/mL. Intra- and inter-day precision ranged from 5.6% to 8.9% for R-(-)-arotinolol and 4.6-7.4% for S-(+)-arotinolol. Accuracy varied from 0.0% to 7.0% for R-(-)-arotinolol and 5.0-10.0% for S-(+)-arotinolol. For R-(-)-arotinolol, the recovery ranged from 87.2% to 99.2% and the matrix factor was 1.03-1.09; for S-(+)-arotinolol, the recovery ranged from 88.0% to 92.4% and the matrix factor was 0.84-0.95, both were not concentration dependent. The method was demonstrated with acceptable accuracy, precision and specificity for the determination of arotinolol enantiomers and has been successfully applied to a stereoselective pharmacokinetic study.