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Development of a useful single-reference HPLC method for therapeutic drug monitoring of phenytoin and carbamazepine in human plasma. ANAL SCI 2023; 39:447-454. [PMID: 36637705 DOI: 10.1007/s44211-023-00266-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Accepted: 12/29/2022] [Indexed: 01/14/2023]
Abstract
A single reference high-performance liquid chromatographic (SR-HPLC) method was developed and validated for the therapeutic drug monitoring (TDM) of phenytoin (PHT) and carbamazepine (CBZ) in plasma from patients. The analytical parameters evaluated were linearity, limit of quantification (LOQ), selectivity, accuracy, and stability according to the US Food and Drug Administration (FDA) guideline. The developed method shows good linearity (r2 > 0.999; LOQ-50 µg/mL), and LOQ values were 1.56 µg/mL for PHT and 0.40 µg/mL for CBZ at 254 nm. For the development of SR-HPLC method, we evaluated to improve the detection wavelength, stirred retention time, and stability for SR, and selected 5-(p-methylphenyl)-5-phenylhydantoin for PHT (relative molar sensitivity, RMS = 0.848) and 10-methoxyiminostilbene for CBZ (RMS = 0.263). The established differential definite quantities of PHT and CBZ in plasma samples were similar using the RMS and absolute calibration methods based on RSD < 5.10%. A preliminary application was performed using chemiluminescent immunoassay and SR-HPLC method, in which the detectable values of the correlation coefficient and the slope of the intercept were PHT: 0.964 and 0.992647, and CBZ: 0.969 and 1.072089, respectively. Based on these results, we propose that the SR-HPLC method with RMS would be offered to the useful and accurate TDM of various medicines in plasma/serum samples.
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Opuni KFM, Boadu JA, Amponsah SK, Okai CA. High performance liquid chromatography: A versatile tool for assaying antiepileptic drugs in biological matrices. J Chromatogr B Analyt Technol Biomed Life Sci 2021; 1179:122750. [PMID: 34237479 DOI: 10.1016/j.jchromb.2021.122750] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2020] [Revised: 04/18/2021] [Accepted: 04/27/2021] [Indexed: 10/21/2022]
Abstract
Epilepsy is a recurrent long-term illness occurring in approximately 1.0% of the world's population. There are currently about 29 approved antiepileptic drugs for the management of epilepsy. Due to narrow therapeutic indices of most antiepileptic drugs, clinical pharmacokinetic characteristics and therapeutic drug monitoring of these drugs are imperative. The objectives of this review were to identify common chromatographic principles, requirements and/or conditions for high-performance liquid chromatography as applied to assay of antiepileptic drugs in biological matrices. The review was conducted using 66 peer reviewed articles (1990 to 2020) from 29 journals that were sought via PubMed, Science Direct and Google Scholar. In all, 29 antiepileptic drugs were assayed from 6 different biological matrices. Forty-three of the reviewed articles estimated the concentration of only one antiepileptic drug, whilst 23 articles focused on simultaneous determination of two or more antiepileptic drugs. Thirty-four, 20, and 14 articles reported using liquid-liquid extraction, protein precipitation, or solid phase extraction for sample clean up, respectively. The ratio of reversed-phase to normal phase, LC-UV to LC-MS and isocratic elution to gradient elution were 61:3, 43:7 and 55:11, respectively. With the exception of one article the reported recoveries ranged from 60.3% to 109.6%. It is noteworthy, that, the performance metrics of high-performance liquid chromatography are better compared to other assays of antiepileptic drugs in biological matrices. This review describes the relevant liquid chromatographic method conditions over the past 30 years for the analysis of this class of drugs, which provides a basis for further method development and optimization.
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Affiliation(s)
- Kwabena F M Opuni
- Department of Pharmaceutical Chemistry, School of Pharmacy, University of Ghana, Ghana.
| | - Joseph A Boadu
- Department of Pharmaceutical Chemistry, School of Pharmacy, University of Ghana, Ghana
| | - Seth K Amponsah
- Department of Medical Pharmacology, University of Ghana Medical School, University of Ghana, Ghana
| | - Charles A Okai
- Department of Laboratory Technology, Faculty of Health Sciences, Kumasi Technical University, Ghana
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A CMOS MEMS-based Membrane-Bridge Nanomechanical Sensor for Small Molecule Detection. Sci Rep 2020; 10:2931. [PMID: 32076079 PMCID: PMC7031247 DOI: 10.1038/s41598-020-60057-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Accepted: 02/05/2020] [Indexed: 11/10/2022] Open
Abstract
Small molecule compounds are necessary to detect with high sensitivity since they may cause a strong effect on the human body even in small concentrations. But existing methods used to evaluate small molecules in blood are inconvenient, costly, time-consuming, and do not allow for portable usage. In response to these shortcomings, we introduce a complementary metal-oxide-semiconductor bio-microelectromechanical system (CMOS BioMEMS) based piezoresistive membrane-bridge (MB) sensor for detecting small molecule (phenytoin) concentrations as the demonstration. Phenytoin is one of anticonvulsant drugs licensed for the management of seizures, which has a narrow therapeutic window hence a level of concentration monitoring was needed. The MB sensor was designed to enhance the structural stability and increase the sensitivity, which its signal response increased 2-fold higher than that of the microcantilever-based sensor. The MB sensor was used to detect phenytoin in different concentrations from 5 to 100 μg/mL. The limit of detection of the sensor was 4.06 ± 0.15 μg/mL and the linear detection range was 5–100 μg/mL, which was within the therapeutic range of phenytoin concentration (10–20 μg/mL). Furthermore, the MB sensor was integrated with an on-chip thermal effect eliminating modus and a reaction tank on a compact chip carrier for disposable utilization. The required amount of sample solution was only 10 μL and the response time of the sensor was about 25 minutes. The nano-mechanical MB sensing method with thermal effect compensation is specific, sensitive, robust, affordable and well reproducible; it is, therefore, an appropriate candidate for detecting small molecules.
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Liu T, Kotha RR, Jones JW, Polli JE, Kane MA. Fast liquid chromatography-tandem mass spectrometry method for simultaneous determination of eight antiepileptic drugs and an active metabolite in human plasma using polarity switching and timed selected reaction monitoring. J Pharm Biomed Anal 2019; 176:112816. [DOI: 10.1016/j.jpba.2019.112816] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2019] [Revised: 08/06/2019] [Accepted: 08/16/2019] [Indexed: 11/15/2022]
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Gao JL, Wang XY, An J, Du CH, Li MJ, Ma HY, Zhang LN, Bian J, Jiang Y. The significance of a new parameter – plasma protein binding – in therapeutic drug monitoring and its application to carbamazepine in epileptic patients. RSC Adv 2017. [DOI: 10.1039/c7ra02991h] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The primary cause of the variability of Cf in pharmacology is the change in plasma protein binding (PPB), thus PPB monitoring should be applied to a better individualization of drug dosage regimens in clinical patients.
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Affiliation(s)
- Jing-lin Gao
- Department of Pharmaceutical Analysis
- School of Pharmacy
- Hebei Medical University
- Shijiazhuang
- China
| | - Xin-yu Wang
- Department of Pharmaceutical Analysis
- School of Pharmacy
- Hebei Medical University
- Shijiazhuang
- China
| | - Jing An
- Department of Pharmacy
- Hebei General Hospital
- Shijiazhuang
- China
| | - Chao-hui Du
- Department of Pharmaceutical Analysis
- School of Pharmacy
- Hebei Medical University
- Shijiazhuang
- China
| | - Meng-jiao Li
- Department of Pharmaceutical Analysis
- School of Pharmacy
- Hebei Medical University
- Shijiazhuang
- China
| | - Hai-yan Ma
- Department of Pharmaceutical Analysis
- School of Pharmacy
- Hebei Medical University
- Shijiazhuang
- China
| | - Li-na Zhang
- Department of Pharmaceutical Analysis
- School of Pharmacy
- Hebei Medical University
- Shijiazhuang
- China
| | - Jing Bian
- Department of Pharmaceutical Analysis
- School of Pharmacy
- Hebei Medical University
- Shijiazhuang
- China
| | - Ye Jiang
- Department of Pharmaceutical Analysis
- School of Pharmacy
- Hebei Medical University
- Shijiazhuang
- China
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Yin L, Wang T, Shi M, Zhang Y, Zhao X, Yang Y, Gu J. Simultaneous determination of ten antiepileptic drugs in human plasma by liquid chromatography and tandem mass spectrometry with positive/negative ion-switching electrospray ionization and its application in therapeutic drug monitoring. J Sep Sci 2016; 39:964-72. [PMID: 26711223 DOI: 10.1002/jssc.201501067] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Revised: 12/19/2015] [Accepted: 12/21/2015] [Indexed: 11/10/2022]
Affiliation(s)
- Lei Yin
- School of Life Science; Jilin University; Changchun PR China
- Clinical Pharmacology Center, Research Institute of Translational Medicine; The First Hospital of Jilin University; Changchun PR China
- Research Center for Drug Metabolism; Jilin University; Changchun PR China
| | - Tingting Wang
- School of Life Science; Jilin University; Changchun PR China
- Clinical Pharmacology Center, Research Institute of Translational Medicine; The First Hospital of Jilin University; Changchun PR China
- Research Center for Drug Metabolism; Jilin University; Changchun PR China
| | - Meiyun Shi
- School of Life and Medical Sciences; Dalian University of Technology; Panjin PR China
| | - Ying Zhang
- Clinical Pharmacology Center, Research Institute of Translational Medicine; The First Hospital of Jilin University; Changchun PR China
| | - Xiaojun Zhao
- Clinical Pharmacology Center, Research Institute of Translational Medicine; The First Hospital of Jilin University; Changchun PR China
| | - Yan Yang
- School of Life Science; Jilin University; Changchun PR China
| | - Jingkai Gu
- Clinical Pharmacology Center, Research Institute of Translational Medicine; The First Hospital of Jilin University; Changchun PR China
- Research Center for Drug Metabolism; Jilin University; Changchun PR China
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Kim KB, Seo KA, Kim SE, Bae SK, Kim DH, Shin JG. Simple and accurate quantitative analysis of ten antiepileptic drugs in human plasma by liquid chromatography/tandem mass spectrometry. J Pharm Biomed Anal 2011; 56:771-7. [DOI: 10.1016/j.jpba.2011.07.019] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Revised: 07/14/2011] [Accepted: 07/18/2011] [Indexed: 11/30/2022]
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Kang J, Park YS, Kim SH, Kim SH, Jun MY. Modern methods for analysis of antiepileptic drugs in the biological fluids for pharmacokinetics, bioequivalence and therapeutic drug monitoring. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2011; 15:67-81. [PMID: 21660146 DOI: 10.4196/kjpp.2011.15.2.67] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2011] [Revised: 04/10/2011] [Accepted: 04/15/2011] [Indexed: 12/20/2022]
Abstract
Epilepsy is a chronic disease occurring in approximately 1.0% of the world's population. About 30% of the epileptic patients treated with availably antiepileptic drugs (AEDs) continue to have seizures and are considered therapy-resistant or refractory patients. The ultimate goal for the use of AEDs is complete cessation of seizures without side effects. Because of a narrow therapeutic index of AEDs, a complete understanding of its clinical pharmacokinetics is essential for understanding of the pharmacodynamics of these drugs. These drug concentrations in biological fluids serve as surrogate markers and can be used to guide or target drug dosing. Because early studies demonstrated clinical and/or electroencephalographic correlations with serum concentrations of several AEDs, It has been almost 50 years since clinicians started using plasma concentrations of AEDs to optimize pharmacotherapy in patients with epilepsy. Therefore, validated analytical method for concentrations of AEDs in biological fluids is a necessity in order to explore pharmacokinetics, bioequivalence and TDM in various clinical situations. There are hundreds of published articles on the analysis of specific AEDs by a wide variety of analytical methods in biological samples have appears over the past decade. This review intends to provide an updated, concise overview on the modern method development for monitoring AEDs for pharmacokinetic studies, bioequivalence and therapeutic drug monitoring.
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Affiliation(s)
- Juseop Kang
- Pharmacology & Clinical Pharmacology Lab, College of Medicine, Hanyang University, Seoul 133-791, Korea
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Santagati NA, Gotti R, Ronsisvalle G. Simultaneous determination of phenytoin and dextromethorphan in urine by solid-phase extraction and HPLC-DAD. J Sep Sci 2005; 28:1157-62. [PMID: 16116992 DOI: 10.1002/jssc.200401942] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
A rapid and simple high-performance liquid chromatographic method with photodiode array detection was developed for the separation and the simultaneous determination of phenytoin and dextromethorphan in human urine. Analysis was performed in less than 4.5 min in isocratic mode on a reversed-phase C18 column (5 microm; 150 x 4.6 mm) using a mobile phase composed of acetonitrile-buffer phosphate 0.01 M (60:40, v/v) adjusted to pH 6.0, at 1 mL/min flow rate and UV absorbance at 210 nm. The elution order of analytes was dextromethorphan (DXM), Internal Standard (IS), and phenytoin (PHT). Calibration curves were linear in the 7.5-25 microg/mL range for PHT and in the 10-30 microg/mL range for DXM. Spike recoveries for urine samples prepared at three spiking levels ranged from 97.8 to 102.3% for PHT and from 94.8 to 100.4% for DXM. The detection limit (LOD) values ranged from 0.08 microg/mL for PHT to 0.5 microg/mL for DXM. The quantitation limit (LOQ) values ranged from 0.3 microg/mL for PHT to 1.6 microg/mL for DXM. The sample preparation method involves a rapid and simple procedure based on solid-phase extraction using a C18 reversed-phase column. Validation of the optimised method was carried out according to the ICH guidelines. The method developed in this study allows the reliable simultaneous analysis of PHT and DXM, drugs that were never quantified together in previously reported analytical methods. The described method has the advantage of being rapid and easy and it could be applied in therapeutic monitoring of these drugs in human urine of epileptic patients.
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Affiliation(s)
- Natale Alfredo Santagati
- Dipartimento di Scienze Farmaceutiche, Facoltà di Farmacia, Università di Catania, Catania, Italy.
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Neels HM, Sierens AC, Naelaerts K, Scharpé SL, Hatfield GM, Lambert WE. Therapeutic drug monitoring of old and newer anti-epileptic drugs. ACTA ACUST UNITED AC 2004; 42:1228-55. [PMID: 15576287 DOI: 10.1515/cclm.2004.245] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
AbstractThe aim of the present paper is to provide information concerning the setting up and interpretation of therapeutic drug monitoring (TDM) for anti-epileptic drugs. The potential value of TDM for these drugs (including carbamazepine, clobazam, clonazepam, ethosuximide, felbamate, gabapentin, lamotrigine, levetiracetam, oxcarbazepine, pheneturide, phenobarbital, phenytoin, primidone, tiagabine, topiramate, valproic acid, vigabatrin and zonisamide) is discussed in relation to their mode of action, drug interactions and their pharmacokinetic properties. The review is based upon available literature data and on observations from our clinical practice. Up until approximately 15 years ago anti-epileptic therapeutics were restricted to a very few drugs that were developed in the first half of the 20th century. Unfortunately, many patients were refractory to these drugs and a new generation of drugs has been developed, mostly as add-on therapy. Although the efficacy of the newer drugs is no better, there is an apparent improvement in drug tolerance, combined with a diminished potential for adverse drug interactions. All new anticonvulsant drugs have undergone extensive clinical studies, but information on the relationship between plasma concentrations and effects is scarce for many of these drugs. Wide ranges in concentrations have been published for seizure control and toxicity. Few studies have been undertaken to establish the concentration-effect relationship. This review shows that TDM may be helpful for a number of these newer drugs.
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Affiliation(s)
- Hugo M Neels
- Laboratory of Biochemistry and Toxicology, Ziekenhuis Netwerk Antwerpen Stuivenberg, Antwerp, Belgium.
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Parant F, Bossu H, Gagnieu MC, Lardet G, Moulsma M. Cross-reactivity assessment of carbamazepine-10,11-epoxide, oxcarbazepine, and 10-hydroxy-carbazepine in two automated carbamazepine immunoassays: PETINIA and EMIT 2000. Ther Drug Monit 2003; 25:41-5. [PMID: 12548143 DOI: 10.1097/00007691-200302000-00006] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
This study was conducted to compare the cross-reactivity of two commercially available carbamazepine (CBZ) immunoassays (PETINIA and EMIT 2000) with carbamazepine-10,11-epoxide (CBZ-E), the active metabolite of CBZ. Oxcarbazepine (OCBZ) and its main metabolite 10-hydroxy-carbazepine (HCBZ) have a chemical structure closely related to that of CBZ. The cross-reactivities of these two drugs were also investigated. In the first part of the study, Lyphocheck blank human serum and Chemonitor quality controls (containing CBZ without CBZ-E) were spiked with variable amounts of CBZ-E. The apparent CBZ levels were measured by PETINIA and EMIT 2000 methods. The interference from OCBZ and HCBZ was directly assessed by measuring the apparent CBZ levels in Chromsystems Trileptal quality controls (containing OCBZ and HCBZ). In the second part of the study, the CBZ levels of serum samples from 49 patients, including 2 patients with massive CBZ ingestion, were measured by immunoassays and compared with a high-pressure liquid chromatography (HPLC) reference technique allowing the simultaneous measurement of CBZ and CBZ-E. The antibody used in the PETINIA assay cross-reacts (about 90%) with CBZ-E. In one case of CBZ poisoning (CBZ and CBZ-E levels measured by HPLC were 26.2 and 18.2 mg/L, respectively), CBZ level measured by PETINIA was falsely elevated (42.5 mg/L). In contrast, the specificity of EMIT 2000 was satisfactory (29.5 mg/L). The two immunoassays tested showed low cross-reactivity with OCBZ and HCBZ. In conclusion, it appears that the CBZ-E metabolite present in samples can falsely increase CBZ levels measured by the PETINIA assay.
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Affiliation(s)
- François Parant
- Laboratory of Biochemistry, Pharmacology and Toxicology, Edouard Herriot Hospital, Lyon, France.
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Rafi JA, Frazier LM, Driscoll-Bannister SM, O'Hara KA, Garnett WR, Pugh CB. Effect of over-the-counter cimetidine on phenytoin concentrations in patients with seizures. Ann Pharmacother 1999; 33:769-74. [PMID: 10466901 DOI: 10.1345/aph.18314] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
OBJECTIVE To determine the effects of the maximum recommended over-the-counter (OTC) cimetidine dosage on phenytoin concentrations in ambulatory seizure patients on long-term phenytoin therapy. METHODS Adults with seizure disorders requiring phenytoin therapy were recruited. Trough total phenytoin concentrations were measured initially and once weekly for six weeks. All assays were performed using Biotrack patient-side cartridges. After a two-week baseline period, patients took cimetidine 200 mg twice daily for two weeks. Toxicity was monitored via weekly neurologic examinations and midweek telephone surveys. Patients were asked to return to clinic weekly during a two-week cimetidine washout period. RESULTS Nine patients entered and completed the study. All but two patients took other anticonvulsants known to interact with phenytoin (carbamazepine, n = 5; phenobarbital, n = 2). No adverse effects or changes in seizure frequency were reported. Paired Student's t-tests revealed no significant difference between serum phenytoin concentrations before (12.3+/-3.2 mg/L [mean +/- SD]) and after (12.8+/-4.0 mg/L) two weeks on the OTC cimetidine regimen. No differences were noted in estimated pharmacokinetic parameters (maximum metabolic rate, Michaelis-Menten constant) for the same time periods (paired Student's t-test, p > 0.05). The Biotrack assay had an r2 = 0.7311 (p < 0.001, two-sided) when compared with TDx. CONCLUSIONS It is possible that the lack of change in phenytoin concentrations was a result of the low daily dosage of cimetidine used or other factors related to the "real world" setting of the study. However, the potential for a serious drug interaction occurring in patients taking long-term oral phenytoin and OTC cimetidine appears to be small.
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Affiliation(s)
- J A Rafi
- School of Pharmacy, Virginia Commonwealth University, Richmond 23298, USA
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Bhatti MM, Hanson GD, Schultz L. Simultaneous determination of phenytoin, carbamazepine, and 10,11-carbamazepine epoxide in human plasma by high-performance liquid chromatography with ultraviolet detection. J Pharm Biomed Anal 1998; 16:1233-40. [PMID: 9571541 DOI: 10.1016/s0731-7085(97)00265-3] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The Bioanalytical Chemistry Department at the Madison facility of Covance Laboratories, has developed and validated a simple and sensitive method for the simultaneous determination of phenytoin (PHT), carbamazepine (CBZ) and 10,11-carbamazepine epoxide (CBZ-E) in human plasma by high-performance liquid chromatography with 10,11 dihydrocarbamazepine as the internal standard. Acetonitrile was added to plasma samples containing PHT, CBZ and CBZ-E to precipitate the plasma proteins. After centrifugation, the acetonitrile supernatant was transferred to a clean tube and evaporated under N2. The dried sample extract was reconstituted in 0.4 ml of mobile phase and injected for analysis by high-performance liquid chromatography. Separation was achieved on a Spherisorb ODS2 analytical column with a mobile phase of 18:18:70 acetonitrile:methanol:potassium phosphate buffer. Detection was at 210 nm using an ultraviolet detector. The mean retention times of CBZ-E, PHT and CBZ were 5.8, 9.9 and 11.8 min, respectively. Peak height ratios were fit to a least squares linear regression algorithm with a 1/(concentration)2 weighting. The method produces acceptable linearity, precision and accuracy to a minimum concentration of 0.050 micrograms ml-1 in human plasma. It is also simple and convenient, with no observable matrix interferences.
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Affiliation(s)
- M M Bhatti
- Covance Laboratories, Madison, WI 53704, USA.
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