Journal of Chromatography B, 821 (2005) 8–14
`
`High performance liquid chromatographic methods for the determination
`of aripiprazole with ultraviolet detection in rat plasma and brain:
`Application to the pharmacokinetic study
`Yoshihiko Shimokawa∗, Hitoshi Akiyama, Eiji Kashiyama,
`Toshihisa Koga, Gohachiro Miyamoto
`Tokushima Research Institute, Otsuka Pharmaceutical Co. Ltd., 463-10 Kagasuno, Kawauchi-cho, Tokushima 771-0192, Japan
`
`Received 28 January 2005; accepted 26 March 2005
`Available online 17 May 2005
`
`Abstract
`
`High performance liquid chromatographic (HPLC) methods were validated for the determination of aripiprazole (OPC-14597, AbilifyTM) in
`rat plasma and brain. Separation was by Nova-pak phenyl column; flow rate, 1.0 ml/min; mobile phase, acetonitrile–methanol–20 mM sodium
`sulfate–acetic acid (27:25:48:1, v/v/v/v); UV detection at 254 nm. Reproducibility in plasma and brain showed excellent precision (within 7.8
`and 10.6%) and accuracy (96.0–102.4% and 99.0–108.7%) with calibration curve ranges 10.0–2000 ng/ml and 30.0–6000 ng/g, respectively.
`Validated HPLC methods were successfully applied to pharmacokinetic study of aripiprazole in rats, demonstrating brain concentrations after
`oral administration five times higher than plasma concentrations.
`© 2005 Elsevier B.V. All rights reserved.
`
`Keywords: Aripiprazole; OPC-14597; AbilifyTM
`
`1. Introduction
`
`Aripiprazole (OPC-14597, AbilifyTM), 7-(4-[4-(2,3-
`dichlorophenyl)-1-piperazinyl]butoxy)-3,4-dihydro-2(1H)-
`quinolinone, was synthesized and screened [1] by Otsuka
`Pharmaceutical Co. Ltd. (Tokyo, Japan) as a novel com-
`pound for the purpose of improving both negative and
`positive symptoms of schizophrenia without
`inducing
`extrapyramidal side effects. Aripiprazole is a novel atypical
`antipsychotic drug [2], and has already been on the market
`in the USA, European countries and several other countries.
`It
`is distinguished from all other antipsychotics by its
`unique pharmacologic profile – i.e. partial agonist activity
`at dopamine D2 receptors [3], partial agonist activity at
`serotonin 5-HT1A receptors [4], and antagonist activity at
`serotonin 5-HT2A receptors [5]. In clinical studies, aripipra-
`zole has been shown to improve both positive and negative
`
`∗ Corresponding author. Tel.: +81 88 665 2126; fax: +81 88 665 6976.
`E-mail address: y shimokawa@research.otsuka.co.jp (Y. Shimokawa).
`
`1570-0232/$ – see front matter © 2005 Elsevier B.V. All rights reserved.
`doi:10.1016/j.jchromb.2005.03.024
`
`symptoms in patients with schizophrenia and schizoaffective
`disorder [6–8]. This novel agent has also demonstrated a
`favorable and excellent safety profile and tolerability with a
`low liability for extrapyramidal symptoms and sedation, and
`no evidence for an increased risk of weight gain, prolactin
`elevation and QTc prolongation [9,10].
`It was thus considered that the measurement of con-
`centrations of aripiprazole in the animal brain was impor-
`tant and worthwhile to understand the profile of aripipra-
`zole in the human. The purpose of this work is to develop
`and validate simple, sensitive and accurate High perfor-
`mance liquid chromatographic (HPLC) methods for mea-
`suring aripiprazole in rat plasma and brain that can be
`used in the study of the distribution of aripiprazole in the
`rat. This is the first published report of analytical meth-
`ods to determine aripiprazole in rat plasma and brain. In
`order to confirm whether the assay methods are accurate,
`the method validation was carried out in compliance with
`the guidance of the US Food and Drug Administration
`[11].
`
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`9
`
`2. Experimental
`
`2.1. Materials
`
`Aripiprazole (OPC-14597, AbilifyTM) and the I.S. (OPC-
`14558) were supplied by Otsuka Pharmaceutical Co. Ltd.
`(Tokyo, Japan). Their chemical structures are shown in Fig. 1.
`Heparinized blank plasma and brain of Sprague–Dawley rat
`were purchased from Kitayama Labes Co. Ltd. (Nagano,
`Japan) and Japan SLC Inc. (Shizuoka, Japan), respectively.
`All other chemicals were of the high purity available com-
`mercially.
`
`2.2. Chromatographic system
`
`The HPLC systems consisted of a LC-10A system
`(Shimadzu, Kyoto, Japan) equipped with a LC-10AD pump,
`a SIL-10AXL auto-injector, a SPD-10A UV detector for
`plasma, and a Waters HPLC system (Waters Associates,
`Milford, MA, USA) equipped with model 510 high-pressure
`pump, a model 717 automatic sample processor, a model
`486 UV detector and a model C-R7A plus chromatopac
`(Shimadzu) for brain. The HPLC separation was achieved
`using a Nova-pak phenyl (150 mm× 3.9 mm i.d., 4 ␮m par-
`ticle size, Waters) at 25 ◦C. The mobile phase was a mixture
`of acetonitrile–methanol–20 mM sodium sulfate–acetic acid
`(27:25:48:1, v/v/v/v). The effluent was monitored with UV
`detection at 254 nm at a flow rate of 1.0 ml/min. The quan-
`tification was accomplished based on the peak height ratio
`of aripiprazole to the I.S. Data calculations were processed
`with a pharmacokinetic data processing system (Otsuka
`Pharmaceutical Co. Ltd.) and a personal computer using
`Excel version 97 from Microsoft Co. (Redmond, WA, USA).
`
`2.3. Preparation of standard solutions and standards
`
`2.3.1. Rat plasma
`Aripiprazole was dissolved in methanol to prepare work-
`ing solutions of 100, 80, 25, 5, 1.25, 1 and 0.5 ␮g/ml. The
`I.S. was dissolved in methanol to prepare a working solution
`of 20 ␮g/ml. Working solutions of aripiprazole and the I.S.
`were stored at 4 ◦C and protected from light, and were stable
`for at least 33 and 39 days, respectively.
`The calibration curves at
`the concentration range of
`10.0–2000 ng/ml were prepared by spiking 10 ␮l of work-
`ing solutions of aripiprazole to 0.5 ml of blank plasma. The
`quality control (QC) samples at eight concentration levels
`(10.0, 20.0, 25.0, 100, 200, 500, 1600 and 2000 ng/ml) were
`also prepared.
`
`2.3.2. Rat brain
`Aripiprazole was dissolved in methanol to prepare work-
`ing solutions of 200, 160, 100, 20, 5, 2 and 1 ␮g/ml. The I.S.
`was dissolved in methanol to prepare a working solution of
`20 ␮g/ml. These working solutions were stored at 4 ◦C and
`protected from light.
`Brain was homogenized with two volumes of physiologi-
`cal saline. The calibration curves at the concentration range
`of 30.0–6000 ng/g were prepared by spiking 10 ␮l of working
`solutions of aripiprazole to 1 ml of blank brain homogenate.
`The QC samples at seven concentration levels (30.0, 60.0,
`150, 600, 3000, 4800 and 6000 ng/g) were also prepared.
`
`2.4. Extraction procedure
`
`2.4.1. Rat plasma
`To 0.5 ml of plasma sample, 10 ␮l of the I.S. working so-
`lution and 100 ␮l of 2 M hydrochloric acid were added. The
`mixture was shaken for 10 min with 5 ml of diethyl ether,
`and centrifuged at 1800× g for 10 min at room temperature.
`After the organic layer was removed, 200 ␮l of 2 M sodium
`hydroxide and 5 ml of diethyl ether were added to the aque-
`ous layer. The mixture was shaken for 10 min again, and
`then centrifuged at 1800× g for 10 min at room tempera-
`ture. Four millilitres of the organic layer was transferred to
`the other clean tube, and evaporated to dryness at 40 ◦C under
`a nitrogen gas stream. The extraction residue was reconsti-
`tuted in 100 ␮l of acetonitrile–methanol–water–acetic acid
`(27:25:48:1, v/v/v/v), and a 30 ␮l aliquot was injected into
`HPLC system.
`
`2.4.2. Rat brain
`To 1 ml of brain homogenate sample, 10 ␮l of the I.S.
`working solution was added. The homogenate was depro-
`teinized with 3 ml of acetonitrile, and centrifuged at 1800× g
`for 10 min at room temperature. The supernatant (3.5 ml) was
`transferred to the other clean tube, and concentrated to re-
`move acetonitrile at 40 ◦C under a nitrogen gas stream, and
`then 100 ␮l of 2 M hydrochloric acid was added. Aripipra-
`zole and the I.S. were extracted in the same manner with the
`plasma.
`
`2.5. Method validation parameters
`
`2.5.1. Selectivity
`Six different blank plasma and brain homogenate samples
`were extracted and analyzed to investigate whether intrinsic
`substances interfere with the analytical system.
`
`Fig. 1. Chemical structures of aripiprazole and the internal standard.
`
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`were stored at −20 ◦C, and analyzed after 0, 3 and 6 months
`in plasma, and 0, 4 and 8 weeks in brain. The stability was
`evaluated by the difference from the mean of initial concen-
`trations, and expressed as the percentage remaining (%).
`
`2.5.2. Calibration curve
`The calibration curve samples were prepared in plasma
`at five concentration levels of 10.0, 25.0, 100, 500 and
`2000 ng/ml for aripiprazole on 7 working days. In brain,
`the calibration curve samples were prepared at 5 concentra-
`tion levels of 30.0, 150, 600, 3000 and 6000 ng/g for arip-
`iprazole on 3 working days. The calibration curves were
`assessed by the coefficients of correlation (r) of the loga-
`rithmic equation using log Y = a log X + b (a: slope, b: inter-
`cept, Y: peak height ratio, X: concentration) and the accuracy
`of the back-calculated concentrations for each concentration
`level.
`
`2.5.3. Lower limit of quantification and intra-day assay
`precision and accuracy
`The QC samples (n = 5) at five concentration levels (10.0,
`25.0, 100, 500 and 2000 ng/ml in plasma, and 30.0, 150, 600,
`3000 and 6000 ng/g in brain) were extracted and analyzed
`by 1 working day. The precision and accuracy were calcu-
`lated for each concentration level to assess the lower limit of
`quantification and the intra-day assay variation.
`
`2.5.4. Inter-day assay precision and accuracy
`The QC samples (n = 15) at three concentration lev-
`els (10.0, 100 and 2000 ng/ml in plasma, and 30.0, 600
`and 6000 ng/g in brain) were extracted and analyzed by 3
`working days. The precision and accuracy were calculated
`for each concentration level to assess the inter-day assay
`variation.
`
`2.5.5. Extraction recovery
`Extraction recovery was evaluated with QC samples
`(n = 3) at two concentration levels (25.0 and 1600 ng/ml in
`plasma, and 60.0 and 4800 ng/g in brain) for aripiprazole, and
`with QC samples (n = 6) at one concentration level (400 ng/ml
`in plasma, and 600 ng/g in brain) for the I.S. Recovery was
`calculated by the comparison with their peak area and the
`corresponding control ones.
`
`2.5.6. Stability of short-term storage
`The stability of aripiprazole in plasma and brain ho-
`mogenate following 24 h at room temperature and three
`freeze (−20 ◦C)/thaw cycles was tested with QC samples
`(n = 3) at two concentration levels (25.0 and 1600 ng/ml in
`plasma, and 60.0 and 4800 ng/g in brain). The QC samples
`kept 24 h at room temperature and after three freeze–thaw
`cycles were analyzed with the control QC ones. The sta-
`bility was evaluated by the difference from the mean of
`control concentrations, and expressed as the percentage
`remaining (%).
`
`2.5.7. Stability of long-term storage
`The stability of aripiprazole in plasma and brain ho-
`mogenate stored at −20 ◦C was tested with QC samples
`(n = 3) at three concentration levels (20.0, 200 and 1600 ng/ml
`in plasma, and 60.0, 600 and 4800 ng/g in brain). The samples
`
`2.6. Application for pharmacokinetic study
`
`Plasma and brain samples were collected at 0.5, 1, 2, 3, 4,
`6, 8 and 12 h after single oral administration of aripiprazole at
`10 and 30 mg/kg to male Sprague–Dawley rats under fasted
`conditions. These samples were stored at −20 ◦C until the
`quantification. The pharmacokinetic parameters, tmax (time to
`maximum concentration), Cmax (maximum concentration),
`AUCth (area under concentration-time curve from 0 h to the
`last observable concentration at time t), t1/2 (apparent elim-
`ination half-life) and brain concentration to plasma concen-
`tration ratio were calculated based on the concentrations of
`aripiprazole in the plasma and brain samples. The pharma-
`cokinetic parameters were calculated by non-compartment
`analysis using WinNonlin Standard (Version 3.1, Pharsight
`Co., CA, USA).
`
`3. Results and discussion
`
`3.1. Development of assay methods
`
`Aripiprazole (OPC-14597, AbilifyTM) was synthesized
`and screened [1] by Otsuka Pharmaceutical Co. Ltd. as a
`novel compound for the purpose of improving both negative
`and positive symptoms of schizophrenia without inducing
`extrapyramidal side effects. As its pharmacological profile,
`the agent was expected to be effective at low doses. There-
`fore, it was necessary to quantify nanogram ranges in plasma
`and brain. In general, HPLC is often used as highly sim-
`ple, sensitive and accurate assay methods for the analysis of
`drugs. We therefore developed HPLC methods for the de-
`termination of aripiprazole with UV detection in rat plasma
`and brain.
`Though the UV absorption spectrum of aripiprazole pos-
`sessed peaks at 217, 254 and 284 nm, 254 nm was selected
`for the assay depending on the absorbance and the interfer-
`ence from biological substances. Aripiprazole and the I.S.
`could be extracted by using diethyl ether under neutral and
`basic conditions, but could not be extracted under acidic con-
`ditions. In order to decrease the interference from biological
`substances in plasma, a washing process by diethyl ether un-
`der acidic conditions was added before the extraction process
`under basic conditions. In brain, the homogenate diluted to
`3 times by saline was used. Acetonitrile was selected as the
`solvent for deproteinization, before the extraction process
`by diethyl ether. There was no interference peak detected in
`the elution positions of aripiprazole and the I.S. for the ex-
`tracted plasma and brain homogenate. The calibration curve
`was constructed in 10.0–2000 ng/ml for plasma, and it was
`constructed in 30.0–6000 ng/g for brain. The HPLC methods
`
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`
`11
`
`developed in rat plasma and brain suggested that validation
`would be achieved.
`
`3.2. Method validation
`
`3.2.1. Selectivity
`Six different lots of plasma and brain homogenate were
`extracted and analyzed as blank samples. The typical chro-
`matograms for the plasma samples are shown in Fig. 2. No
`interference peak was detected in the eluting positions of
`aripiprazole and the I.S. in six blank chromatograms.
`
`3.2.2. Calibration curve
`The parameters for the calibration curve and back-
`calculated concentrations of the calibration curves in plasma
`and brain are shown in Table 1. The calibration curves
`were constructed over 10.0–2000 ng/ml
`in plasma, and
`30.0–6000 ng/g in brain. The coefficients of correlation (r)
`in plasma and brain were 0.9998 and 0.9994, respectively.
`The mean accuracy in the back-calculated concentrations was
`98.5–101.8% in plasma and 96.3–103.2% in brain.
`
`3.2.3. Lower limit of quantification and intra-day assay
`precision and accuracy
`The precision and accuracy at the lower limit of quantifi-
`cation (LLOQ) and the intra-day assay variation in plasma
`and brain are shown in Table 2. The precision at LLOQ
`was 2.0% in plasma and 5.2% in brain. The accuracy at
`LLOQ was 102.0% in plasma and 108.7% in brain. The
`intra-day assay precision was within 2.0% in plasma and
`within 10.6% in brain, and the intra-day assay accuracy was
`96.0–102.4% in plasma and 99.0–108.7% in brain. The meth-
`ods in plasma and brain showed excellent reproducibility and
`accuracy.
`
`3.2.4. Inter-day assay precision and accuracy
`The precision and accuracy of the inter-day assay varia-
`tion in plasma and brain are shown in Table 3. The inter-day
`assay precision was within 7.8% in plasma and within 9.6%
`in brain. The inter-day assay accuracy was 96.0–102.0% in
`plasma and 99.8–104.0% in brain. The methods showed ex-
`cellent reproducibility and accuracy.
`
`Fig. 2. HPLC chromatograms of extracted rat plasma. (a) Blank plasma, (b)
`plasma spiked with 10.0 ng/ml of aripiprazole (LLOQ) and the I.S., and (c)
`plasma spiked with 2000 ng/ml of aripiprazole and the I.S. The retention
`times of aripiprazole and the I.S. are 7.8 and 10.2 min, respectively.
`
`3.2.5. Extraction recovery
`The extraction recovery of aripiprazole and the I.S. from
`rat plasma and brain homogenate is shown in Table 4. The
`mean recovery of aripiprazole was 87.2–91.1% in plasma
`and 41.3–43.5% in brain. The mean recovery of the I.S.
`was 87.7% in plasma and 36.9% in brain. The reason for
`the lower recovery of both compounds from brain as com-
`
`Table 1
`Calibration curve parameters and back-calculated concentrations of the calibration curves for aripiprazole in rat plasma and brain
`Matrix
`Calibration curves
`Back-calculated concentrations (ng/ml)
`Curve parameters
`
`Plasma
`
`Mean (n = 7)
`Accuracy (%)
`
`10.0
`9.97
`99.7
`
`25.0
`25.0
`100.0
`
`100
`100
`100.0
`
`500
`509
`101.8
`
`2000
`1970
`98.5
`
`Matrix
`
`Calibration curves
`
`Back-calculated concentrations (ng/g)
`
`Brain
`
`6000
`3000
`600
`150
`30.0
`Mean (n = 3)
`6070
`2890
`619
`154
`29.4
`101.2
`96.3
`103.2
`102.7
`98.0
`Accuracy (%)
`The data result from the analysis on 7 and 3 working days in plasma and brain samples, respectively.
`
`Slope
`0.9710
`–
`
`Intercept
`0.5657
`–
`
`Curve parameters
`
`Slope
`1.0135
`–
`
`Intercept
`−2.5984
`–
`
`r
`0.9998
`–
`
`r
`0.9994
`–
`
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`

`12
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`
`Table 2
`Lower limit of quantification and intra-day assay precision and accuracy for aripiprazole in rat plasma and brain
`Matrix
`Concentration added (ng/ml)
`Concentration found (ng/ml)
`Precision (%)
`Plasma
`10.0
`10.2
`2.0
`25.0
`24.2
`1.7
`100
`100
`1.0
`500
`512
`0.2
`2000
`1920
`1.0
`
`Matrix
`Brain
`
`Concentration found (ng/g)
`Concentration added (ng/g)
`32.6
`30.0
`162
`150
`599
`600
`2970
`3000
`6010
`6000
`Concentration found and accuracy represent the mean values.
`
`Table 3
`Inter-day assay precision and accuracy for aripiprazole in rat plasma and brain
`Matrix
`Concentration added (ng/ml)
`Concentration found (ng/ml)
`Plasma
`10.0
`10.2
`100
`97.8
`2000
`1920
`
`Matrix
`Brain
`
`Concentration found (ng/g)
`Concentration added (ng/g)
`31.2
`30.0
`603
`600
`5990
`6000
`Concentration found and accuracy represent the mean values.
`
`Precision (%)
`5.2
`5.6
`3.3
`10.6
`3.7
`
`Precision (%)
`5.9
`3.3
`7.8
`
`Precision (%)
`9.6
`4.3
`5.0
`
`Accuracy (%)
`102.0
`96.8
`100.0
`102.4
`96.0
`
`Accuracy (%)
`108.7
`108.0
`99.8
`99.0
`100.2
`
`Accuracy (%)
`102.0
`97.8
`96.0
`
`Accuracy (%)
`104.0
`100.5
`99.8
`
`n
`5
`5
`5
`5
`5
`
`n
`5
`5
`5
`5
`5
`
`n
`15
`15
`15
`
`n
`15
`15
`15
`
`pared to plasma is unclear, but it is thought that this may be
`because some brain components are being adsorbed to test
`substances.
`
`3.2.6. Stability of short-term storage
`The results of short-term stability of aripiprazole in plasma
`and brain homogenate kept for 24 h at room temperature and
`after three freeze–thaw cycles are shown in Table 5. The mean
`values of the percentage remaining kept for 24 h at room
`temperature were 98.8–107.4% in plasma, and 94.0–100.6%
`in brain. The mean values of the percentage remaining af-
`ter 3 freeze–thaw cycles were 95.2–106.1% in plasma, and
`97.9–99.2% in brain. These results showed that aripiprazole
`
`was stable in rat plasma and brain homogenate kept for 24 h
`at room temperature and after three freeze–thaw cycles.
`
`3.2.7. Stability of long-term storage
`The results of long-term stability of aripiprazole in plasma
`and brain homogenate stored at −20 ◦C are shown in Table 6.
`The mean values of the percentage remaining in plasma
`stored for 6 months were 100.9–111.1%, and the percent-
`age remaining in brain stored for 8 weeks were 93.9–99.1%.
`These data showed that aripiprazole was stable for at least
`6 months in plasma and for 8 weeks in brain after long-term
`storage at −20 ◦C.
`
`Table 4
`Extraction recovery of aripiprazole and the I.S. from rat plasma and brain
`Matrix
`Analyte
`Concentration added (ng/ml)
`Plasma
`Aripiprazole
`25.0
`1600
`400
`
`I.S.
`
`Matrix
`Brain
`
`Analyte
`Aripiprazole
`
`I.S.
`Recovery represents the mean values.
`
`Concentration added (ng/g)
`60.0
`4800
`600
`
`Recovery (%)
`87.2
`91.1
`87.7
`
`Recovery (%)
`41.3
`43.5
`36.9
`
`Precision (%)
`2.4
`3.7
`2.5
`
`Precision (%)
`7.3
`3.0
`5.7
`
`n
`3
`3
`6
`
`n
`3
`3
`6
`
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`Y. Shimokawa et al. / J. Chromatogr. B 821 (2005) 8–14
`
`Table 5
`Short-term stability of aripiprazole in rat plasma and brain homogenate kept for 24 h at room temperature and during three freeze–thaw cycles
`Matrix
`Concentration added (ng/ml)
`Mean of percentage remaining (%)
`
`Plasma
`
`Matrix
`
`Brain
`
`25.0
`1600
`
`24 h at room temperature
`107.4
`98.8
`
`Three freeze–thaw cycles
`106.1
`95.2
`
`Concentration added (ng/g)
`
`Mean of percentage remaining (%)
`
`60.0
`4800
`
`24 h at room temperature
`100.6
`94.0
`
`Three freeze–thaw cycles
`97.9
`99.2
`
`Table 6
`Long-term stability of aripiprazole in rat plasma and brain homogenate stored at −20 ◦C
`Matrix
`Concentration added (ng/ml)
`Mean of percentage remaining (%)
`
`Plasma
`
`Matrix
`
`Brain
`
`20.0
`200
`1600
`
`3 months
`105.1
`96.9
`98.9
`
`6 months
`100.9
`105.3
`111.1
`
`Concentration added (ng/g)
`
`Mean of percentage remaining (%)
`
`60.0
`600
`4800
`
`4 weeks
`99.7
`98.6
`101.8
`
`8 weeks
`93.9
`98.2
`99.1
`
`13
`
`n
`
`3
`3
`
`n
`
`3
`3
`
`n
`
`3
`3
`3
`
`n
`
`3
`3
`3
`
`Table 7
`Pharmacokinetic parameters of aripiprazole in plasma and brain after single oral administration of aripiprazole at 10 and 30 mg/kg to male rats
`tmax (h)
`Cmax (ng/ml)
`t1/2
`t1/2 calculated range (h)
`Matrix
`Dose (mg/kg)
`AUCth (ng h/ml)
`Plasma
`10
`2
`86
`2496h
`2.2
`2–6
`1.9
`4–12
`30
`4
`442
`304412h
`
`Matrix
`Brain
`
`Cmax (ng/g)
`tmax (h)
`AUCth (ng h/g)
`Dose (mg/kg)
`1,0746h
`390
`2
`10
`14,81712h
`2232
`3
`30
`All pharmacokinetic parameters are calculated from the mean plasma and brain concentrations.
`
`t1/2
`1.8
`2.0
`
`t1/2 calculated range (h)
`2–6
`3–12
`
`3.3. Application for pharmacokinetic study
`
`The validated HPLC methods were successfully applied
`to the pharmacokinetic study of aripiprazole in rats. Mean
`concentrations of aripiprazole in plasma and brain after single
`oral administration of aripiprazole at 10 and 30 mg/kg to male
`rats are shown in Fig. 3. The pharmacokinetic parameters of
`aripiprazole are shown in Table 7. The maximum plasma con-
`centration (Cmax) of aripiprazole at 10 and 30 mg/kg doses
`reached 86 and 442 ng/ml, respectively, at 2 and 4 h after the
`dosing, and declined with t1/2 of 2.2 and 1.9 h. AUCth for
`10 and 30 mg/kg were 249 and 3044 ng h/ml, respectively.
`On the other hand, the maximum brain concentration (Cmax)
`of aripiprazole at 10 and 30 mg/kg doses reached 390 and
`2232 ng/g, respectively, at 2 and 3 h after the dosing, and de-
`clined with t1/2 of 1.8 and 2.0 h. AUCth for 10 and 30 mg/kg
`were 1074 and 14817 ng h/g, respectively. Brain concentra-
`tions were about five times higher than plasma concentra-
`
`Fig. 3. Mean concentrations of aripiprazole in plasma and brain after single
`oral administration of aripiprazole at 10 and 30 mg/kg to male rats. Each
`data point represents the mean of four animals.
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`
`tions in both doses. These results suggest that aripiprazole is
`rapidly absorbed and penetrated into the brain.
`
`4. Conclusion
`
`HPLC methods for the determination of aripiprazole
`(OPC-14597, AbilifyTM) with UV detection in rat plasma
`and brain were developed and validated. The methods in
`plasma and brain showed excellent reproducibility and ac-
`curacy with the calibration curve ranges of 10.0–2000 ng/ml
`and 30.0–6000 ng/g, respectively. The validated HPLC meth-
`ods were successfully applied to the pharmacokinetic study
`of aripiprazole in rats. The pharmacokinetic study demon-
`strates that aripiprazole is extensively distributed in rat brain.
`
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