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Journal of Bioequivalence & Bioavailability

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Determination of Aprepitant in Human Plasma by Using LC-MS/MS with Electrospray Ionization

Ravi Prakash PVDLS1*, Sumadhuri B2 and Srikanth M3

1Actimus Biosciences Private Limited, 3rd and 4th floor, Varun towers, Kasturbamarg, Siripuram, Visakhapatnam, Andhra Pradesh, India

2Department of Pharmaceutical Analysis and Quality Assurance, Bapatla College of Pharmacy, Bapatla, Andhra Pradesh, India

3Department of Pharmaceutical Sciences, A.U College of pharmaceutical Sciences, Andhra University, Andhra Pradesh, India

*Corresponding Author:
Ravi Prakash PVDLS
Actimus Biosciences Private Limited
3rd and 4th floor, Varun towers, Kasturbamarg
Siripuram, Visakhapatnam, Andhra Pradesh, India
Tel: 91-9848490302
Fax: 91-8916672111
E-mail: [email protected]

Received Date: February 23, 2013; Accepted Date: March 25, 2013; Published Date: March 31, 2013

Citation: JRavi Prakash PVDLS, Sumadhuri B, Srikanth M (2013) Determination of Aprepitant in Human Plasma by Using LC-MS/MS with Electrospray Ionization. J Bioequiv Availab 5:110-116. doi: 10.4172/jbb.1000143

Copyright: © 2013 Ravi Prakash PVDLS, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited..

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Abstract

A precise, sensitive and high throughput liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for determination of Aprepitant (APT) in human plasma was developed and validated using Quetiapine (QTP) as internal standard. The analyte and internal standard were extracted from human plasma using liquid-liquid extraction. Chromatographic separation was performed on Discovery C18 10 cm×4.6 mm, 5 μm column with an isocratic mobile phase composed of 5 mM Ammonium Acetate (pH 4.00):Acetonitrile (10:90), at a flow-rate of 0.9 ml/ min. The MS-MS detection was performed on a AB Sciex API 3200 tandem mass spectrometer operated in Multiple reaction monitoring (MRM) at positive mode at m/z 535.10/277.10 and 384.00/253.10 for APT and QTP respectively. A linear dynamic range of 10.004-5001.952 ng/ml for APT was evaluated with mean correlation coefficient (r) of 0.9991. The precision of the assay (expressed as coefficient of variation, CV) was less than 15% at concentrations of LQC, MQC, HQC and was less than 20% for LLOQQC. Percent recoveries for APT at high, middle and low quality control samples was found to be 71.9%, 68.0%, and 63.8% respectively and for internal standard 77.7%. The analyte was found to be stable throughout five freeze-thawing cycles, bench top, wet extract, dry extract, auto sampler and interim stability studies. Therefore, the proposed method was found to be suitable for the routine quality control analysis of Aprepitant in human plasma in bioequivalence studies.

Keywords

Aprepitant; Quetiapine; LC-MS/MS; Validation

Introduction

Aprepitant (APT) is chemically (5-[[2(R)-[1(R)-(3,5- bistrifluoromethylphenyl)ethoxy]-3(S)-(4-fluorophenyl) morpholin- 4-yl]methyl]-2,4-dihydro-[1,2,4]triazol-3-one) and belongs to class of substance P antagonists (SPA). It acts as an anti-emetic by blocking the neurokinin 1 (NK1) receptor. NK1 is a G protein-coupled receptor which is located in the central and peripheral nervous system having a dominant ligand known as substance P (SP). SP is found in high concentrations in the vomiting centre of brain and results in vomiting when activated. APT crosses blood-brain barrier and blocks SP by occupying NK1 receptors in brain neurons [1]. Thus, APT is used for the prevention of acute, delayed chemotherapy-induced and postoperative nausea and vomiting. It has little or no affinity towards 5-HT3 receptors but it is shown to increase the activity of 5-HT3 receptor antagonists such as ondansetron and the corticosteroid dexamethasone, which are also used to prevent nausea and vomiting caused by chemotherapy [2]. It has been recently demonstrated that substance P (SP) and neurokinin -1 (NK1) receptor antagonists induce cell proliferation and cell inhibition in human melanoma cells [3]. NK1 receptor antagonists might also reverse the impairment of NK cell function found in HIV infection via antagonism against SP, whose effects are mediated through NK1 receptor [4]. Currently, APT is also under evaluation as a new therapy in Neuro AIDS patients from the Integrated Preclinical and Clinical Program (IPCP) grant mechanism supported by the NIH at the Children’s Hospital of Philadelphia and University of Pennsylvania [5].

Literature review reveals that very few analytical methods have been established for the estimation of APT. Estimation of impurities and Diastereomers in APT bulk drug substance [6], Characterization and Quantization of APT drug substance polymorphs by Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy [7], stability of an extemporaneous oral liquid APT formulation [8], estimation of APT capsules by RP-HPLC [9], Stability-indicating HPLC method for quantitative analysis of APT [3,10] were reported. Metabolic disposition of Aprepitant in rats and dogs was also reported [11]. Estimation of APT in rhesus macaque plasma, cerebral spinal fluid and in human plasma by LC-MS method was reported [12]. Other liquid chromatography and tandem mass spectroscopy methods for determination of APT in human plasma were also recently reported [13,14]. The present study describes development and validation of a simple, specific, rapid and sensitive liquid chromatography - tandem mass spectrometry (LC-MS/MS) method for the determination of Aprepitant in human plasma with a limit of quantification (LOQ) of 10.004 ng/ml during a 2.5 min run time using QTP as internal standard. The structures of Aprepitant and Quetiapine are displayed in figure 1.

bioequivalence-bioavailability-trazodone

Figure 1: Structures of Trazodone and Quetiapine.

Materials and Methods

Reagents and chemicals

Aprepitant (APT) (99.21% purity), was obtained from Roorkee Research & Analytical Labs Pvt.Ltd. and Quetiapine (QTP) (99.56% purity) from Splendid Labs Pvt.Ltd., Pune, India. Methanol of HPLC grade obtained from Merck, Mumbai India. Acetonitrile and Tertiary Butyl Methyl Ether (TBME) of HPLC grade, Ammonium Acetate, Formic acid and Ammonia of GR/AR grade were purchased from Fisher scientific Pvt. Ltd., Mumbai, India. High purity water was prepared through a Milli-Q water purification system.

Instrumentation

LC-MS/MS analysis was performed using API 3200 triple quadrupole instrument (Applied Biosystems SCIEX, Toronto, Canada) coupled with Shimadzu HPLC system (Shimadzu SIL HTC, USA) in multiple reaction monitoring (MRM) mode. Electron spray ionization in positive mode was used for ionization. Data processing was performed on Analyst software version 1.5.1. A high-speed desk centrifuge Sorvall Legend XTR Thermo Scientific was used to centrifuge the samples. Ultra microbalance SE2 of Sartorius and Semi Microbalance CPA225D of Sartorius was used for weighing the samples.

MS/MS conditions

The APT and QTP had Multiple reaction monitoring (MRM) at m/z 535.10/277.10 and 384.00/253.10 respectively. The tuned MS/MS conditions of APT and QTP were represented in table 1. The mass spectrum of drug and IS are displayed in figures 2 and 3.

PARAMETER APREPITANT QUETIAPINE
Declustering potential (DP) 30 40
Entrance potential (EP) 10 10
Collision cell entrance potential (CEP) 26.37 21.38
Collision energy (CE) 55
Collision cell exit potential (CXP) 5
Curtain gas (CUR) 30
Collision associated dissociation (CAD) 6
Ion spray voltage (ISV) 4500
Heater temperature (TEM) 475.00°C
Nebulizer gas (GS1) 40
Heater gas (GS2) 45

Table 1: Tuned MS/MS conditions of APT and QTP.

bioequivalence-bioavailability-spectrums

Figure 2: Full scan mass spectrums of Trazodone parent ion and product ion.

bioequivalence-bioavailability-quetiapine

Figure 3: Full scan mass spectrums of Quetiapine parent ion and production.

Chromatographic conditions

The separation of the compounds was made on Discovery C18 10 cm×4.6 mm, 5 μm column. A mixture of 5 mM Ammonium Acetate (pH 4.00): Acetonitrile (10:90) was used as mobile phase and was filtered through 0.45 μ membrane filters before use and degassed in an ultrasonic bath. All analysis was performed under isocratic condition at a flow rate of 0.9 ml/min at ambient temperature. The sample volume injected was 10 μl with run time of 2.5 min. Under the chromatographic conditions described above, both APT and QTP were eluted with retention times of 1.55 min and 1.70 min (Figure 4).

bioequivalence-bioavailability-retention

Figure 4: Retention time of Trazodone and Quetiapine.

Preparation of standards and quality control samples

The primary stock solutions of APT and QTP of 1000 μg/ml were prepared in methanol. The stock solution of internal standard was diluted to concentration of 400 ng/ml by using diluent 50% v/v methanol in water. The stock solution of APT was then serially diluted with 50% v/v methanol in water to provide working standard solution of desired concentration. Standard stock solutions of APT were added to drug free human plasma to obtain calibration curve concentration levels of 10.004, 20.008, 500.195, 1508.429, 2432.950, 3201.249, 4001.562 and 5001.952 ng/ml. In a similar way, spiking of aqueous quality control dilutions was done in human plasma to prepare the quality control samples of concentrations 10.576 ng/ml (LLOQ QC), 25.181 ng/ml (LQC), 2098.448 ng/ml (MQC) and 3605.580 ng/ml (HQC). Primary stock solutions were kept at 2-8°C when not in use. All matrix based samples shall be stored in the deep freezer at –70°C ± 15°C.

Sample preparation method

Required set of calibration curve standards and QC’s were withdrawn from deep freezer and allowed them to thaw at room temperature. Thawed samples were vortexed to ensure complete mixing of contents. 50 μl of internal standard solution (400 ng/ml) was taken into a RIA vial tube and 300 μl of plasma sample was added to it and vortexed. 100 μl of 2.0% (v/v) Ammonia solution was added to the above RIA vial and vortexed. To it 2.5 ml of the Tertiary Butyl Methyl Ether (TBME) solution was added and vortexed at 2000 rpm for about 10 minutes. The samples were centrifuged for 10 min at 4000 rpm at 10°C. 2.0 ml of supernatant layer from the centrifuged samples was taken into separate RIA vial. The samples were evaporated until dryness under the Nitrogen evaporator with 50°C of temperature. The samples were reconstituted with 300 μl of mobile phase. Then the samples were transferred into auto injector and 10 μl of sample was injected.

By using above materials and methods validation parameter were performed (i.e Auto sample carryover, Matrix effect, Precision and Accuracy, recovery and stability in matrix etc.)

Results and Discussion

Method validation

Validation runs were conducted according to the guidance of USFDA [15], on six consecutive days. Each validation run consisted of a minimum of one set of calibration standards and six sets of QC plasma samples at four concentrations of LLOQ QC, LQC, MQC and HQC.

Auto sample carryover and Matrix effect with IS normalizing factor

There was no carryover was observed by using optimised above LC-MS/MS and sample processing condition. Matrix ion suppression or enhancement effects on the MRM LC-MS/MS sensitivity were evaluated by the post extraction sicked samples. Different plasma lot Ob blank was extracted according to our sample extraction procedure. And then spiked Th analyte and internal standard into these matrixes. From the tach lot, three samples at two concentration (HQC and LQC) level were prepared. All these extracted and post extract spicked were analyzed by LC-MS/MS. It was observing matrix effect and IS normalizing factor for both analyte and internal standard accuracy ± 15%. The results were represented in tables 2a-2d.

Matrix ID HPM/130/12 HPM/131/12 HPM/133/12 HPM/134/12 HPM/164/12 HPM/165/12
HQC LQC HQC LQC HQC LQC HQC LQC HQC LQC HQC LQC
  614429 11790 621408 12122 619934 11708 616694 11386 605133 11253 583671 11043
623405 11773 605263 11195 604992 10925 582814 11269 618123 11527 590071 10717
608829 11491 615390 11573 603769 11461 621443 11642 594887 10677 603499 10866
N 3 3 3 3 3 3 3 3 3 3 3 3
Average 615554.3 11684.7 614020.3 11630 609565 11364.7 606983.7 11432.3 606047.7 11152.3 592413.7 10875.3
Standard Deviation 7352.87 167.94 8159.18 466.12 9000.61 400.29 21065.8 190.77 11644.97 433.85 10119.46 163.2
CV (%) 1.2 1.4 1.3 4.0 1.5 3.5 3.5 1.7 1.9 3.9 1.7 1.5

Table 2a: Results for matrix effect of Aprepitant.

Matrix ID HPM/130/12 HPM/131/12 HPM/133/12 HPM/134/12 HPM/164/12 HPM/165/12
HQC LQC HQC LQC HQC LQC HQC LQC HQC LQC HQC LQC
  157796 142794 154361 143363 157647 144131 156453 142050 150725 145502 155087 134696
154518 141267 151610 138063 157484 136738 153487 137155 151886 138790 149717 132549
154836 138796 157496 138351 155391 140020 155092 140002 153526 129473 152937 130175
N 3 3 3 3 3 3 3 3 3 3 3 3
Average 155716.7 140952.3 154489 139925.7 156840.7 140296.3 155010.7 139735.7 152045.7 137921.7 152580.3 132473.3
Standard Deviation 1807.76 2017.49 2945.09 2980.3 1258.09 3704.24 1484.67 2458.34 1407.31 8049.7 2702.71 2261.45
CV (%) 1.2 1.4 1.9 2.1 0.8 2.6 1 1.8 0.9 5.8 1.8 1.7

Table 2b: Results for matrix effect of Quetiapine.

PLASMA ID Aprepitant Quetiapine IS Normalized Factor
EXT AQS MF EXT AQS MF
HPM/130/12 615554.3 581308 1.06 155716.7 146851 1.06 1.01
HPM/131/12 614020.3 587921 1.06 154489 148046 1.05 1.01
HPM/133/12 609565.0 583943 1.05 156840.7 147853 1.07 1.00
HPM/134/12 606983.7 578207 1.05 155010.7 148541 1.05 1.00
HPM/164/12 606047.7 580871 1.04 152045.7 145224 1.03 0.99
HPM/165/12 592413.7 570523 1.02 152580.3 146949 1.04 0.97
Average 607430.78 580462.17 1.047 154447.18 147244 1.05 0.997
Standard deviation 8265.515 5873.769 0.0151 1839.145 1184.75 0.0141 0.0151
%CV 1.4 1.0 1.4 1.2 0.8 1.3 1.5

Table 2c: Results for IS Normalized factor at HQC level.

PLASMA ID Aprepitant Quetiapine IS Normalized Factor
EXT AQS MF EXT AQS MF
HPM/130/12 615554.3 581308 1.06 155716.7 146851 1.06 1.01
HPM/131/12 614020.3 587921 1.06 154489 148046 1.05 1.01
HPM/133/12 609565.0 583943 1.05 156840.7 147853 1.07 1.00
HPM/134/12 606983.7 578207 1.05 155010.7 148541 1.05 1.00
HPM/164/12 606047.7 580871 1.04 152045.7 145224 1.03 0.99
HPM/165/12 592413.7 570523 1.02 152580.3 146949 1.04 0.97
Average 607430.78 580462.17 1.047 154447.18 147244 1.05 0.997
Standard deviation 8265.515 5873.769 0.0151 1839.145 1184.75 0.0141 0.0151
%CV 1.4 1 1.4 1.2 0.8 1.3 1.5

Table 2d: Results for IS Normalized factor at LQC level.

Linearity and Lower Limits of Quantification (LLOQ)

Calibration curves were prepared by assaying plasma samples at eight concentrations of APT ranging 10.004 - 5001.952 ng/ml with correlation coefficient (r) of 0.9991 (Figure 5). The linearity of each calibration curve was determined by plotting the peak area ratio(y) of APT to QTP versus the nominal concentration (x) of ATP. The calibration curves were constructed by weighed (1/x2) least square linear regression. The limit of detection was defined (3.3 ng/ml), as analyte responses are at least five times the response compared to blank responses. The lowest standard on the calibration curve 10.004 ng/ ml was defined as limit of quantification since the analyte peak was identifiable, discrete and reproducible with a precision of less than or equal to 20% and accuracy of 80-120% (Figure 6).

bioequivalence-bioavailability-calibration

Figure 5: Calibration curve of Trazodone.

bioequivalence-bioavailability-trazodone

Figure 6: STD 1 of Trazodone and IS.

bioequivalence-bioavailability-trazodone

Figure 7: STD 8 of Trazodone and IS.

Precision and accuracy

The method precision and accuracy were evaluated by using replicate analysis of QC’s at four concentrations of LLOQQC, LQC, MQC and HQC. Intra-day evaluation was done on the same day, whereas interday was done on consecutive days. Inter day batch accuracy ranged from 90.6% to 106.3%. Inter day batch precision ranged from 2.4% to 10.8%. Intraday batch accuracy ranged from 91.5% to 103.7%. Intraday batch precision ranged from 2.0% to 7.9%. The mean concentration, standard deviation (SD), coefficient of variation (%CV) was evaluated and their results were tabulated in tables 3a and 3b.

Batch Concentration in ng/ml Mean Detected Concentration, ± SD (ng/ml) Mean Accurracy (%) %CV
Intraday P&A 3605.580 3586.306 ± 13.54 99.5 0.4
2098.450 2084.240 ± 7.88 99.3 0.4
25.181 24.276 ± 1.22 96.4 6.3
10.576 9.187 ± 0.08 86.9 8.2
Interday P&A 3605.580 3592.114 ± 9.91 99.6 0.3
2098.450 2082.542 ± 4.55 99.2 0.2
25.181 22.651 ± 1.18 90.0 5.2
10.576 9.137 ± 0.32 86.4 3.6

Table 3a: Intra- and Inter- day Precision and Accuracy of Aprepitant sipcked in human plasma.

PARAMETERS HQC MQC LQC LLOQ QC
Nominal Conc. 3605.58 2098.45 25.181 10.576
Mean 3589.69 2083.77 23.542 9.166
SD (±) 18.1303 8.6949 1.1647 0.9706
CV (%) 0.5 0.4 4.9 10.6
Accuracy 99.6 99.3 93.5 86.7

Table 3b: Precision and Accuracy studies of APT samples (ng/ml). LLOQQC – Lower limit of quantification Quality control samples, LQC - Lower Quality Control, MQC - Medium Quality Control, HQC - Higher Quality Control, SD - Standard Deviation and CV - Coefficient of variance.

Extraction recovery

Recovery analysis was repeated for six replicates at three concentrations (LQC, MQC and HQC). The extraction recovery of APT from spiked samples were determined by comparing the peak areas of analytes or internal standard in extracted samples to the corresponding peak areas of analytes or internal standard in post extracted spiked samples (extracted blank samples followed by spiking analyte and internal standard at a concentration level equivalent to 100% recovery). The results were represented in table 4.

Drug Nominal conc. % Recovery Standard deviation % CV
Aprepitant        
HQC 3605.580 ng/ml 71.9 4.661 6.5
MQC 2098.448 ng/ml 68.0 2.585 3.8
LQC 25.181 ng/ml 63.8 2.718 4.3
Quetiapine 400 ng/ml 77.7 4.333 5.6

Table 4: Extraction recovery data of analyte and internal standard.

Re-injection reproducibility

The Re injection Reproducibility evaluation is done by comparing the results of re-injected set of samples with that of the original set and results were represented in table 5.

Observed Concentration(ng/ml)
Parameter HQC LQC
Average Conc. 3595.66 23.952
Standard Deviation 5.4635 0.7881
CV (Precision %) 0.2 3.3
Nominal Conc. 3605.58 25.181
Accuracy (%) 99.7 95.1

Table 5: Results for reinjection reproducibility.

Stability studies

Stability studies were carried out for stock solutions, stock dilutions and spiking solutions by comparing fresh stock and stability stock. Six replicates of each Low quality control (LQC) and high quality control (HQC) samples were processed, analyzed and quantified against freshly prepared calibration curve. The precision and accuracy for the stability samples must be within ≤ 15 and ± 15% of their respective nominal concentrations. Stability in biological matrix was carried for the following and the results were represented in table 6.

STABILITIES TIME % STABILITY
HQC LQC
Freeze-thaw 5 cycles 96.3 98.9
Bench top 17 h 92.3 94.3
Wet extract at refrigerator 41 h 95.9 96.1
Wet extract at bench top 17 h 95.3 100.5
Dry extract 41 h 94.9 92.8
Auto sampler 41 h 101.4 96.9
Interim 03 days 104.9 101.5

Table 6: Results for Stability Studies.

Freeze-thaw stability was obtained by taking the samples from the deep freezer at –70°C ± 15°C over five freeze-thaw cycles. The bench top stability was evaluated by keeping replicates of the LQC and HQC samples were withdrawn from deep freezer, kept at room temperature approximately for 17 hours (hrs). Wet extract stability of the samples evaluated at room temperature and refrigerator approximately for 17 hrs and 41 hrs respectively. Dry extract stability of the samples evaluated at refrigerator conditions for 41 hrs. Auto injector stability was evaluated for 41 hrs. Samples were initially stored in -25°C and later retrieved after 03 days. The samples were then processed and analyzed.

Conclusion

A highly selective and rapid LCMS/MS method employing liquid– liquid extraction for the determination of APT in human plasma has been developed and validated with a Lower limit of Quantification of 10.004 ng/ml. The validation data also demonstrates good precision, accuracy and high extraction efficiency. The validated method allows quantification of APT in the linear range of 10.004-5001.952 ng/ml. In conclusion, this paper describes a very simple and sensitive LCMS/ MS method for the quantization of APT suitable to monitor plasma concentrations during clinical pharmacokinetic and bioequivalence studies in humans.

Acknowledgement

The author would like to thank Actimus Biosciences Pvt.Ltd., India for the technical support. The author is indebted to Professors Dr. I.Mrityunjaya Rao and Dr. N.Someswara Rao for the fruitful discussion. The author gratefully acknowledges the competent technical assistance of M.Srinivasa Reddy and S.Vijay Bhaskar Reddy.

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