Reliable and sensitive determination of dutasteride in human plasma by liquid chromatography-tandem mass spectrometry.

An accurate and precise method was developed and validated using LC-MS/MS to quantify dutasteride in human plasma. The analyte and dutasteride-13C6 as internal standard (IS) were extracted from 300 µL plasma volume using methyl tert-butyl ether-n-hexane (80:20, v/v). Chromatographic analysis was performed on a Gemini C18 (150 × 4.6 mm, 5 µm) column using acetonitrile-5 mm ammonium formate, pH adjusted to 4.0 with formic acid (85:15, v/v) as the mobile phase. Tandem mass spectrometry in positive ionization mode was used to quantify dutasteride by multiple reaction monitoring. The entire data processing was done using Watson LIMS(TM) software, which provided excellent data integrity and high throughput with improved operational efficiency. The calibration curve was linear in the range of 0.1-25 ng/mL, with intra-and inter-batch values for accuracy and precision (coefficient of variation) ranging from 95.8 to 104.0 and from 0.7 to 5.3%, respectively. The mean overall recovery across quality controls was ≥95% for the analyte and IS, while the interference of matrix expressed as IS-normalized matrix factors ranged from 1.01 to 1.02. The method was successfully applied to support a bioequivalence study of 0.5 mg dutasteride capsules in 24 healthy subjects. Assay reproducibility was demonstrated by reanalysis of 103 incurred samples.

Simultaneous quantitation of HIV-protease inhibitors ritonavir, lopinavir and indinavir in human plasma by UPLC-ESI-MS-MS.

A selective, sensitive and high-throughput ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS-MS) method has been developed and validated for the quantification of HIV-protease inhibitors ritonavir (RTV), lopinavir (LPV) and indinavir (IDV) in human plasma. Sample clean-up involved protein precipitation of both drugs and fluconazole used as internal standard from 100 µL human plasma. All the analytes were chromatographically separated on a Waters Acquity UPLC BEH C18 (2.1 × 50 mm, 1.7 µm particle size) analytical column using 0.1% formic acid and methanol (40:60, v/v) as the mobile phase. The parent → product ion transitions for ritonavir (m/z 721.40→ 296.10), lopinavir (m/z 629.40→ 447.40) and indinavir (m/z 614.4→ 421.0) IS (m/z 307.10 → 220.10) were monitored on a triple quadrupole mass spectrometer, operating in the multiple reaction monitoring and positive ion mode. The method was validated over the concentration range of 30-15,000 ng/mL for LPV and IDV and 3-1500 ng/mL for RTV. The method was successfully applied to a pilot bioequivalence study in 36 healthy human subjects after oral administration of lopinavir 200 mg and ritonavir 50 mg tablet formulation under fasting conditions.

Validated ultra-performance liquid chromatography tandem mass spectrometry method for the determination of pramipexole in human plasma.

A sensitive and high throughput ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS-MS) method has been developed for the determination of pramipexole, a dopamine agonist, in human plasma. Sample preparation involved liquid-liquid extraction of pramipexole and ranitidine as the internal standard (IS) in ethyl acetate from 100 µL human plasma. The chromatographic separation is achieved on a Waters Acquity UPLC BEH C18 (100 mm × 2.1 mm, 1.7 µm) analytical column using an isocratic mobile phase, consisting of 10 mM ammonium formate (pH 7.50)-acetonitrile (15:85, v/v), at a flow-rate of 0.5 mL/min. The precursor → product ion transition for pramipexole (m/z 212.1 → 153.0) and IS (m/z 315.0 → 176.1) were monitored on a triple quadrupole mass spectrometer, operating in the multiple reaction monitoring (MRM) and positive ion mode. The method was validated over a wide dynamic concentration range of 20-4020 pg/mL. Matrix effect is assessed by post-column infusion experiment and the process efficiency were 91.9% and 85.7% for pramipexole and IS, respectively. The method is rugged and rapid with a total run time of 1.5 min and is applied to a bioequivalence study of 0.25 mg PPX tablet formulation in 30 healthy Indian male subjects under fasting condition.

Application of a rapid and selective method for the simultaneous determination of protease inhibitors, lopinavir and ritonavir in human plasma by UPLC-ESI-MS/MS for bioequivalence study in Indian subjects.

A high throughput and rugged ultra performance liquid chromatography tandem mass spectrometry (UPLC-ESI-MS/MS) method is developed and validated for the selective determination of protease inhibitors -- lopinavir (LPV) and ritonavir (RTV) in human plasma. Plasma samples were prepared by solid phase extraction of the analytes and their deuterated analogs as internal standard (IS) using Waters Oasis HLB cartridges. The chromatographic separation was achieved in a run time of 1.2 min on Waters Acquity UPLC BEH C18 column (50 mm x 2.1 mm, 1.7 microm) under isocratic conditions. The mobile phase consisted of 10 mM ammonium formate, pH 4.0 adjusted with formic acid and methanol (10:90, v/v). The protonated precursor --> product ion transitions for lopinavir, ritonavir, d(8)-lopinavir and d(6)-ritonavir were monitored on a triple quadrupole mass spectrometer, operating in the multiple reaction monitoring (MRM) and positive ion mode. A linear dynamic range of 2.9-1452 ng/mL and 29.6-14379 ng/mL was established for ritonavir and lopinavir respectively using 0.1 mL human plasma. The mean relative recovery of lopinavir (96.6%), ritonavir (97.5%), d(8)-lopinavir (85.5%) and d(6)-ritonavir (86.3%) from spiked plasma samples was consistent and reproducible. The method was successfully applied to a bioequivalence study of [200(lopinavir)+50(ritonavir)]mg tablet formulation in 36 healthy human subjects under fasting conditions.