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Police A, Shankar VK, Narasimha Murthy S. RP-HPLC method for simultaneous estimation of vigabatrin, gamma-aminobutyric acid and taurine in biological samples. J Chromatogr B Analyt Technol Biomed Life Sci 2018; 1076:44-53. [DOI: 10.1016/j.jchromb.2018.01.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 01/02/2018] [Accepted: 01/06/2018] [Indexed: 12/13/2022]
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Matar KM, Abdel‐Hamid ME. Quantification of Vigabatrin in Human Plasma by Liquid Chromatography–Electrospray Tandem Mass Spectrometry. J LIQ CHROMATOGR R T 2011. [DOI: 10.1081/jlc-200044519] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
- Kamal M. Matar
- a Department of Applied Therapeutics, Faculty of Pharmacy , Kuwait University , Safat, Kuwait
| | - Mohammed E. Abdel‐Hamid
- b Department of Pharmaceutical Chemistry, Faculty of Pharmacy , Kuwait University , Safat, Kuwait
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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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Bentué-Ferrer D, Tribut O, Verdier MC. Suivi thérapeutique pharmacologique du vigabatrin. Therapie 2010; 65:23-7. [DOI: 10.2515/therapie/2009067] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2009] [Accepted: 12/01/2009] [Indexed: 11/20/2022]
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Musenga A, Mandrioli R, Comin I, Kenndler E, Raggi MA. Determination of vigabatrin in human plasma by means of CE with LIF detection. Electrophoresis 2007; 28:3535-41. [PMID: 17828800 DOI: 10.1002/elps.200700139] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
A method has been developed for the quantitation of the antiepileptic drug vigabatrin (VGB) in human plasma. It is based on CE with LIF detection. The effect of the pH of the buffer and of N-methylglucamine (GLC) as BGE constituent was investigated. The final BGE consisted of 50 mM borate buffer, pH 9.0, with 100 mM GLC and enabled separation within 12 min at 20 kV voltage. An SPE procedure was used for the pretreatment of biological samples, based on mixed-mode lipophilic-cation exchange cartridges, followed by a derivatization step with 6-carboxyfluorescein-N-succinimidyl ester (CFSE). Fluorescence was excited by an Ar-ion laser (lambda(exc) = 488 nm). Linearity was observed in the 10-120 microg/mL plasma concentration range. Extraction yield was >96%, precision (expressed as RSD) <6.7% and accuracy (recovery) was between 97.0 and 101.6%. The method has been successfully applied to the analysis of VGB in plasma of epileptic patients undergoing therapy with the drug.
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Affiliation(s)
- Alessandro Musenga
- Pharmaco-Toxicological Analysis Laboratory, Department of Pharmaceutical Sciences, Alma Mater Studiorum-University of Bologna, Via Belmeloro 6, I-40126 Bologna, Italy
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Franco V, Mazzucchelli I, Fattore C, Marchiselli R, Gatti G, Perucca E. Stereoselective determination of vigabatrin enantiomers in human plasma by high performance liquid chromatography using UV detection. J Chromatogr B Analyt Technol Biomed Life Sci 2007; 854:63-7. [PMID: 17481975 DOI: 10.1016/j.jchromb.2007.03.042] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2006] [Revised: 03/19/2007] [Accepted: 03/30/2007] [Indexed: 11/30/2022]
Abstract
A rapid and simple high-performance liquid chromatographic method for the determination of the R-(-)- and S-(+)-enantiomers of the antiepileptic drug vigabatrin in human plasma is described. After adding the internal standard (1-aminomethyl-cycloheptyl-acetic acid), plasma samples (200 microL) are deproteinized with acetonitrile and the supernatant is derivatized with 2,4,6 trinitrobenzene sulfonic acid (TNBSA). Separation is achieved on a reversed-phase cellulose-based chiral column (Chiralcel-ODR, 250 mm x 4.6 mm i.d.) using 0.05 M potassium hexafluorophosphate (pH 4.5)/acetonitrile/ethanol (50:40:10 vol/vol/vol) as mobile phase at a flow-rate of 0.9 mL/min. Chromatographic selectivity is improved by concentrating the derivatives on High Performance Extraction Disk Cartridges prior to injection. Detection is at 340 nm. Calibration curves are linear (r(2)> or =0.999) over the range of 0.5-40 microg/mL for each enantiomer, with a limit of quantification of 0.5 microg/mL for both analytes. The assay is suitable for therapeutic drug monitoring and for single-dose pharmacokinetic studies in man.
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Affiliation(s)
- Valentina Franco
- Clinical Pharmacology Unit, Department of Internal Medicine and Therapeutics, University of Pavia, Pavia, Italy
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Juergens UH, May TW, Rambeck B. Simultaneous HPLC Determination of Vigabatrin and Gabapentin in Serum with Automated Pre-Injection Derivatization. J LIQ CHROMATOGR R T 2006. [DOI: 10.1080/10826079608007195] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Uwe H. Juergens
- a Department of Biochemistry , Epilepsy Research Foundation , Bethel/Maraweg 13, D-33617, Bielefeld, Germany
| | - Theodor W. May
- a Department of Biochemistry , Epilepsy Research Foundation , Bethel/Maraweg 13, D-33617, Bielefeld, Germany
| | - Bernhard Rambeck
- a Department of Biochemistry , Epilepsy Research Foundation , Bethel/Maraweg 13, D-33617, Bielefeld, Germany
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Borrey DCR, Godderis KO, Engelrelst VIL, Bernard DR, Langlois MR. Quantitative determination of vigabatrin and gabapentin in human serum by gas chromatography-mass spectrometry. Clin Chim Acta 2005; 354:147-51. [PMID: 15748611 DOI: 10.1016/j.cccn.2004.11.023] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2004] [Revised: 11/18/2004] [Accepted: 11/22/2004] [Indexed: 11/25/2022]
Abstract
BACKGROUND Published methods for routine clinical monitoring of vigabatrin and gabapentin are often very laborious. A simple GC-MS method was developed for the simultaneous quantitative determination of vigabatrin and gabapentin in human serum. METHODS After protein precipitation, the compounds are derivatized by methylation and analysed on a polydimethylsiloxane column using splitless injection. Cyclobarbital is used as the internal standard. To attain maximal sensitivity, detection is performed in selected ion monitoring mode. RESULTS The method was fully validated and linear calibration curves were obtained in the concentration ranges from 5 to 80 microg/mL for vigabatrin and from 5 to 30 microg/mL for gabapentin. The within-day and day-to-day relative standard deviations at three different concentration levels were <10% and <15%, respectively. The limit of quantitation was 2 mug/mL for both compounds. CONCLUSIONS The presented method provides high chromatographic resolution, good sensitivity and unequivocal identification potential and can be used for simultaneous analysis of both antiepileptics.
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Affiliation(s)
- Daniëlle C R Borrey
- Toxicology Unit, Department of Clinical Chemistry, AZ Sint-Jan AV, Ruddershove 10, B-8000 Brugge, Belgium.
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Lin FM, Kou HS, Wu SM, Chen SH, Wu HL. Capillary electrophoresis analysis of gabapentin and vigabatrin in pharmaceutical preparations as ofloxacin derivatives. Anal Chim Acta 2004. [DOI: 10.1016/j.aca.2004.07.022] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Chang SY, Lin WC. Determination of vigabatrin by capillary electrophoresis with laser-induced fluorescence detection. J Chromatogr B Analyt Technol Biomed Life Sci 2003; 794:17-22. [PMID: 12888194 DOI: 10.1016/s1570-0232(03)00396-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
A new analytical method for vigabatrin based on capillary electrophoretic separation and laser-induced fluorescence detection has been developed. 5-Carboxytetramethylrhodamine succinimidyl ester was used for precolumn derivatization of the non-fluorescent drug. Optimal separation and detection were obtained with an electrophoretic buffer of 50 mM sodium borate (pH9.5) containing 10 mM sodium dodecyl sulfate and a green He-Ne laser (excitation at 543.5 nm, emission at 589 nm). The concentration limit of detection in aqueous solution was 24 nM. Combined with a simple cleanup procedure, this method can be applied to the determination of vigabatrin in human plasma. A calibration curve ranging from 1.5 to 200 microM shown to be linear. Both the within-day and day-to-day reproducibilities and accuracies were less then 14.3% and 4.9% respectively. The limit of detection of vigabatrin in plasma was about 0.13 microM
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Affiliation(s)
- Sarah Y Chang
- Department of Applied Chemistry, Chaoyang University of Technology, County, Wufeng, Taichung, Taiwan 413.
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Johannessen SI, Battino D, Berry DJ, Bialer M, Krämer G, Tomson T, Patsalos PN. Therapeutic drug monitoring of the newer antiepileptic drugs. Ther Drug Monit 2003; 25:347-63. [PMID: 12766564 DOI: 10.1097/00007691-200306000-00016] [Citation(s) in RCA: 223] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The aim of the present review is to discuss the potential value of therapeutic drug monitoring (TDM) of the newer antiepileptic drugs (AEDs) felbamate, gabapentin, lamotrigine, levetiracetam, oxcarbazepine, tiagabine, topiramate, vigabatrin, and zonisamide. Studies of the relationship between serum concentrations and clinical efficacy of these drugs are reviewed, and the potential value of TDM of the drugs is discussed based on their pharmacokinetic properties and mode of action. Analytical methods for the determination of the serum concentrations of these drugs are also briefly described. There are only some prospective data on the serum concentration-effect relationships, and few studies have been designed primarily to study these relationships. As TDM is not widely practiced for the newer AEDs, there are no generally accepted target ranges for any of these drugs, and for most a wide range in serum concentration is associated with clinical efficacy. Furthermore, a considerable overlap in drug concentrations related to toxicity and nonresponse is reported. Nevertheless, the current tentative target ranges for felbamate, gabapentin, lamotrigine, levetiracetam, oxcarbazepine (10-hydroxy-carbazepine metabolite), tiagabine, topiramate, vigabatrin, and zonisamide are 125 to 250 micromol/L, 70 to 120 micromol/L, 10 to 60 micromol/L, 35 to 120 micromol/L, 50 to 140 micomol/L, 50 to 250 nmol/L, 15 to 60 micromol/L, 6 to 278 micromol/L, and 45 to 180 micromol/L, respectively. Further systematic studies designed specifically to evaluate concentration-effect relationships of the new AEDs are urgently needed. Although routine monitoring in general cannot be recommended at present, measurements of some of the drugs is undoubtedly of help with individualization of treatment in selected cases in a particular clinical setting.
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Affiliation(s)
- Svein I Johannessen
- The National Center for Epilepsy, Sandvika, Norway, "Carlo Besta", Milan, Italy.
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Chollet DF. Determination of antiepileptic drugs in biological material. J Chromatogr B Analyt Technol Biomed Life Sci 2002; 767:191-233. [PMID: 11885851 DOI: 10.1016/s0378-4347(01)00502-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Current analytical methodologies applied to the determination of antiepileptic drugs in biological material are reviewed. The role of chromatographic techniques is emphasized. Special attention is focused on new chemical entities as well as current trends such as high-speed liquid chromatographic techniques, hyphenated techniques and electrochromatography techniques. A review with 542 references.
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Affiliation(s)
- Daniel F Chollet
- Covance Central Laboratory Services SA, Drug Monitoring Department, Meyrin/Geneva, Switzerland.
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Belal F, Abdine H, Al-Majed A, Khalil NY. Spectrofluorimetric determination of vigabatrin and gabapentin in urine and dosage forms through derivatization with fluorescamine. J Pharm Biomed Anal 2002; 27:253-60. [PMID: 11682233 DOI: 10.1016/s0731-7085(01)00503-9] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
A stability-indicating, sensitive, simple and selective spectrofluorimetric method was developed for the determination of vigabatrin (VG) and gabapentin (GB). The method is based on the reaction between the two drugs and fluorescamine in borate buffer of pH 8.2 to give highly fluorescent derivatives that are measured at 472 nm using an excitation wavelength of 390 nm for both drugs. The optimum conditions were ascertained and the method was applied for the determination of VG and GB over the concentration range of 0.20-4.00 and 0.1-1.0 microg/ml, respectively with detection limits of 0.05 microg/ml (2.9 x 10(-7) M) and 0.06 microg/ml (2.3 x 10(-7) M) for VG and GB, respectively. The suggested method was applied, without any interference from the excipients, to the determination of the two drugs in their pharmaceutical formulations. Furthermore, the method was extended to the in-vitro determination of both drugs in spiked human urine. Interference from endogenous amino acids could be eliminated through selective complexation with copper acetate, the % recovery (n=4) is 98.0 +/- 7.05. Co-administered drugs such as lamotrigine, phenobarbitone, valproic acid, clopazam, carbamazepine, clonazepam and cimitidine did not interfere with the assay. The method is also stability-indicating; as the degradation product of vigabatrin: 5-vinylpyrrolidin-2-one, produced no interference with its analysis.
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Affiliation(s)
- F Belal
- Department of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, PO Box 2457, 11451, Riyadh, Saudi Arabia.
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Affiliation(s)
- P N Patsalos
- University Department of Clinical Neurology, National Hospital for Neurology and Neurosurgery, London, UK
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Ratnaraj N, Patsalos PN. A high-performance liquid chromatography micromethod for the simultaneous determination of vigabatrin and gabapentin in serum. Ther Drug Monit 1998; 20:430-4. [PMID: 9712469 DOI: 10.1097/00007691-199808000-00013] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
A gradient high-performance liquid chromatography micromethod is described for the simultaneous quantitation of vigabatrin and gabapentin in human serum. Chromatography was performed using a 125- x 3-mm ID Hypersil BDS C-18 column with a 3-microm mini-bore, eluted with a gradient system comprised of phosphate buffer (pH 6.5)-acetonitrile-methanol-water at a flow rate of 0.45 ml/minute. The column eluent was monitored on a fluorescence detector using excitation and emission wavelengths of 340 and 440 nm, respectively. The lower limit of quantitation for vigabatrin and for gabapentin was 5 micromol/l, and the within-batch and between-batch coefficients of variation were <5%. No interference from commonly prescribed antiepileptic drugs (carbamazepine and its metabolite carbamazepine epoxide, oxcarbazepine and its metabolite 10-hydroxycarbazepine, ethosuximide, lamotrigine, phenobarbitone, phenytoin, primidone, and valproic acid) was observed; thus, the method can be used to monitor vigabatrin and gabapentin in patients on polytherapy antiepileptic drug regimens.
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Affiliation(s)
- N Ratnaraj
- University Department of Clinical Neurology, Institute of Neurology, London, United Kingdom
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Abstract
gamma-Aminobutyric acid (GABA) was first proposed as a putative inhibitory neurotransmitter by Elliot and van Gelder in 1958. Since then, numerous efforts have been made to find ways to increase GABA at its receptor sites, based on the findings that decreased GABA results in convulsions in animals and that agents enhancing GABA-mediated functions can have antiepileptic effects. However, the relationship between GABA levels and seizures is not simple. Seizures can occur even in the presence of elevated GABA levels. Indeed, it is possible that regional biochemical differences in the brain can be important. The antiepileptic effects of GABA depend on the mechanism whereby GABA-mediated inhibition is enhanced. Since the 1970s, several compounds have been developed that are designed to act in some manner on the GABA system. These compounds affect GABA-mediated inhibition at different levels and appear to have varied effects, depending on their mechanism of action. To date, specific antiepileptic drugs (AEDs) with potential GABA-inhibitory effects have been designed either to have GABA agonist properties, to inhibit GABA catabolism, to inhibit GABA uptake, or to facilitate GABA release or facilitate GABAA receptor activity. Vigabatrin (VGB) was designed specifically to inhibit GABA transaminase and thereby increase the availability of GABA in the brain. Study data and clinical experience over the past 14 years have demonstrated VGB to be an effective AED.
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Affiliation(s)
- E Ben-Menachem
- Department of Neurology, Sahlgren University Hospital, Göteborg, Sweden
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Abstract
We have reviewed the pharmacokinetics of six antiepileptic drugs that are marketed (felbamate, gabapentin, lamotrigine, oxcarbazepine, vigabatrin, and zonisamide) and six drugs that are undergoing evaluation (levetiracetam, ralitoline, remacemide, stiripentol, tiagabine, and topiramate). In addition, we have compared the prodrugs eterobarb and fosphenytoin and the controlled-release formulations of valproic acid and carbamazepine with their parent compounds. Finally, we have devised a scoring system to compare the pharmacokinetics of new antiepileptic drugs. Using this system, vigabatrin, levetiracetam, gabapentin, and topiramate appea to have the most favourable pharmacokinetic profiles, whilst ralitoline and stiripentol have the least favourable.
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Affiliation(s)
- M C Walker
- University Department of Clinical Neurology, Institute of Neurology, London, UK
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Yarrington JT, Gibson JP, Dillberger JE, Hurst G, Lippert B, Sussman NM, Heydorn WE, Marler RJ. Sequential neuropathology of dogs treated with vigabatrin, a GABA-transaminase inhibitor. Toxicol Pathol 1993; 21:480-9. [PMID: 8115824 DOI: 10.1177/019262339302100507] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Vigabatrin (Sabril) is a gamma-aminobutyric acid-transaminase (GABA-T) inhibitor that is effective in the treatment of certain types of drug-resistant or uncontrolled epilepsy but is known to cause microscopic vacuolation (intramyelinic edema) in the brains of treated rats, mice, and dogs. The effects of high oral doses (300 mg/kg/day) of vigabatrin administered orally to Beagle dogs were studied during treatment weeks 1-12 and recovery weeks 13, 14, 16, 20, 24, and 28. Emesis, loose stools, and anorexia and 3 drug-related deaths were observed during the first 4 wk of treatment but were virtually nonexistent thereafter because of adaptation to the drug aided by food supplementation. In more sensitive areas of the brain (columns of the fornix, thalamus, and hypothalamus), microscopic quantitative differences between background vacuolation in controls and drug-related vacuolation in treated dogs could be delineated after 4 wk, generally reached highest levels of severity between 8 and 12 wk, and were reversible upon cessation of dosing. Inhibition of brain GABA-T and elevation of brain GABA were noted after 1 wk of treatment. During the course of treatment vigabatrin ranged between 4-17 nmol/ml (plasma) and 42-1,570 nmol/ml [cerebrospinal fluid (CSF)] while CSF GABA concentrations were 4-32 nmol/ml (treated dogs) and 0.1-0.6 nmol/ml (control dogs). Although the cause of vigabatrin-induced microvacuolation is unknown, the results of the study demonstrated that GABA-T inhibition with subsequent GABA elevation occurred within the first week of treatment and was followed by the onset of detectable microvacuolation several weeks later.
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Abstract
During the past few years a major increase has taken place in the number of drugs which have become available in the antiepileptic arsenal. In fact, 3 new antiepileptic drugs, vigabatrin, oxcarbazepine and lamotrigine, were recently approved in several European countries. Two other drugs, felbamate and gabapentin, are expected to be approved in the US in the near future. This review comparatively evaluates the pharmacokinetics of the following 10 new antiepileptic drugs: felbamate, flunarizine, gabapentin, lamotrigine, oxcarbazepine, remacemide, stiripentol, tiagabine, topiramate and vigabatrin. Three of the new drugs, gabapentin, topiramate and vigabatrin, are more promising on the basis of their pharmacokinetic features. They are well absorbed, excreted mainly unchanged in the urine, and are not susceptible to enzyme induction or inhibition. Their drug interaction potential appears to be minimal. About 50% of felbamate is excreted unchanged, with the rest eliminated by metabolism. The remaining drugs are eliminated by metabolic processes such as glucuronidation (lamotrigine), deglycine formation (remacemide) or oxidative metabolism (flunarizine and stiripentol). Oxcarbazepine and remacemide have high hepatic clearance and are biotransformed to hydroxy and deglycine metabolites, respectively, with the activity of their metabolites contributing to the antiepileptic activity of the parent drug after oral administration, despite high first-pass effect metabolism. Gabapentin and oxcarbazepine do not behave pharmacokinetically as their original design intended. Gabapentin is not effective as a chemical drug delivery system for gamma-aminobutyric acid (GABA), and oxcarbazepine serves as a prodrug to its hydroxy metabolite, but does not act as a drug on its own. Nevertheless, these 2 agents demonstrate efficacy in extensive preclinical and clinical trials. Although the pharmacokinetics features of these drugs are important, these features are secondary to their pharmacodynamic properties--i.e. to the requirement that new antiepileptic drugs have to have proven clinical efficacy and safety in epileptic patients.
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Affiliation(s)
- M Bialer
- Department of Pharmacy, School of Pharmacy, Faculty of Medicine, Hebrew University of Jerusalem, Israel
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Hoke JF, Yuh L, Antony KK, Okerholm RA, Elberfeld JM, Sussman NM. Pharmacokinetics of vigabatrin following single and multiple oral doses in normal volunteers. J Clin Pharmacol 1993; 33:458-62. [PMID: 8331204 DOI: 10.1002/j.1552-4604.1993.tb04688.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The pharmacokinetics of vigabatrin were investigated after single and multiple oral doses in two groups of 24 healthy male volunteers. Vigabatrin was well tolerated by the volunteers; headache was the most frequently reported adverse event. There were no clinically remarkable changes in serum chemistry, urinalysis, or hematology attributable to vigabatrin. For the single-dose study, a stepwise linear contrast method was used to assess dose proportionality. The results showed that vigabatrin exhibited dose linear pharmacokinetics after single oral doses ranging from 0.5 to 4.0 g. Slight changes in the terminal phase half-life and renal clearance were evident in the higher dosage groups. These changes with increasing dose of vigabatrin were relatively minor and not considered to be clinically important. Evaluation of the multiple-dose pharmacokinetics indicated that vigabatrin exhibited dose linearity over the range of 0.5 to 2.0 g administered every 12 hours. The terminal phase half-life and renal clearance of vigabatrin during multiple dosing were consistent with that after single doses. During multiple dosing, steady-state concentrations of vigabatrin were reached on the second day of dosing, and drug accumulation was minimal.
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Affiliation(s)
- J F Hoke
- Department of Clinical Pharmacology, Glaxo Inc., Research Triangle Park, NC 27709
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Abstract
This review discussed various analytical methods for the determination of antiepileptic drugs and their metabolites in biological tissues. The emphasis was on the reports published since their last review [J. T. Burke and J. P. Thenot, J. Chromatogr., 340 (1985) 199]. Both chromatographic and immunological procedure were cited and compared. Methods for individual and simultaneous quantitation of standard antiepileptic drugs and their metabolites were considered. In addition, a discussion of free drug determination and procedures for new candidate antiepileptic drugs were included.
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Affiliation(s)
- I M Kapetanovic
- Preclinical Pharmacology Section, NINDS, NIH, Bethesda, MD 20892
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Browne TR, Mattson RH, Penry JK, Smith DB, Treiman DM, Wilder BJ, Ben-Menachem E, Miketta RM, Sherry KM, Szabo GK. A multicentre study of vigabatrin for drug-resistant epilepsy. Br J Clin Pharmacol 1989; 27 Suppl 1:95S-100S. [PMID: 2667606 PMCID: PMC1379686 DOI: 10.1111/j.1365-2125.1989.tb03468.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
1. Vigabatrin (GVG) was given in a single-blind fashion to 89 patients with complex partial seizures (CPS) refractory to conventional drugs. 2. The median number of CPS per month decreased from 11.0 to 5.0 after addition of GVG, and 51% of patients had a 50% or greater decrease in CPS frequency (P less than 0.001). 3. Side effects (principally drowsiness, ataxia, headache) occurred mainly during the initiation of therapy and decreased during therapy. After 12 weeks on GVG side effects significantly interfered with functioning in only 13% of patients, and the efficacy: toxicity ratio warranted continued administration in 74% of patients. 4. Co-administration of GVG resulted in a mean decrease of 20% in phenytoin serum concentration (P less than 0.001). 5. Sixty-six patients having a favourable response to GVG during the single-blind study have been followed for 6-54 (median 33) months on GVG. Only 17 patients have dropped out of long-term follow-up due to break through seizures and/or side effects. No serious systemic or neurological toxicity has been detected.
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Affiliation(s)
- T R Browne
- Department of Neurology, Veterans Administration Medical Center, Boston, MA 02130
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B'Hymer C. Static headspace gas chromatographic method for the determination of residual solvents in vigabatrin drug substance. J Chromatogr A 1988; 438:103-7. [PMID: 3379113 DOI: 10.1016/s0021-9673(00)90238-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- C B'Hymer
- Merrell Dow Research Institute, Cincinnati, OH 45215
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Chen TM, Contario JJ, Fike RR. High-performance liquid chromatographic assay for vigabatrin and its primary degradation product in a pharmaceutical tablet formulation. J Chromatogr A 1987; 398:351-4. [PMID: 3654849 DOI: 10.1016/s0021-9673(01)96525-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- T M Chen
- Merrell Dow Research Institute, Cincinnati, OH 45215
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