Capillary gas chromatography-mass spectrometry of valproic acid metabolites in serum and urine using tert.-butyldimethylsilyl derivatives

Abbott, Frank S.; Kassam, Jeanine; Acheampong, Andrew; Ferguson, Sheila; Panesar, Sukhbinder Kaur; Burton, R.; Farrell, Kevin; Orr, James

doi:10.1016/s0378-4347(00)83721-4

Cited by 38 publications

(7 citation statements)

References 15 publications

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“…An intricate metabolic pattern, as well as clinical and pharmacokinetic considerations, contributes to which were comparable to those reported by other investigators for pediatric (Abbott et al, 1986) and adult patients (Tatsuhara et al, 1987), appeared stable over time for most patients in this study, transient deviations in the pattern in serum (2-en, 3-en, and 2,3'-dien were markedly increased, whereas other metabolite levels were in the normal range) were noted in two patients in association with hepatomegaly , liver enzyme abnormalities, and febrile infection. Dexamethasone but not CBZ was used as additional medication in these two patients.…”

Section: Discussionsupporting

confidence: 87%

Valproate Metabolites in Serum and Urine During Antiepileptic Therapy in Children with Infantile Spasms: Abnormal Metabolite Pattern Associated with Reversible Hepatotoxicity

et al. 1992

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The purpose of this study was to identify abnormal metabolite patterns of valproate (VPA) as possible early indicators of VPA-induced liver toxicity. In a prospective study, we determined serum and urine levels of VPA metabolites by gas chromatography-mass spectrometry (GC-MS) during the course of therapy in 25 children treated for infantile spasms with high VPA doses (less than or equal to 100 mg/kg body weight/day). Most patients had similar metabolite profiles: The main metabolites in serum were the beta-oxidation products (2-en-VPA and 3-keto-VPA) and the major diunsaturated metabolite 2,3'-dien-VPA. Glucuronide conjugates and the oxidation products represent the most abundant metabolites in urine. Other metabolites, including the potential hepatotoxin 4-en-VPA, were detected only in low concentrations. Two children had transiently aberrant metabolite profiles, indicating altered beta-oxidation, (levels of 2-en-VPA, 2,3'-dien-VPA, and 3-en-VPA were markedly increased) in connection with hepatomegaly and increased liver enzyme activities at a time when both had febrile infections and were receiving dexamethasone comedication. At no time were increased levels of 4-en-VPA or its derivatives detected. Establishing the VPA metabolite profile may aid in evaluation of patients who show signs and symptoms of liver dysfunction during VPA therapy. The present study shows that initial stages of hepatotoxicity reactions to VPA may be accompanied by characteristic changes in VPA metabolism; early detection of such abnormal metabolite patterns might decrease the risk of severe hepatic injury.

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Section: Discussionsupporting

confidence: 87%

Valproate Metabolites in Serum and Urine During Antiepileptic Therapy in Children with Infantile Spasms: Abnormal Metabolite Pattern Associated with Reversible Hepatotoxicity

et al. 1992

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“…Several derivatives of phenacyl, including trimethylsilyl (TMS), t-butyldimethylsilyl (t-BDMS) and 9-aminophenanthrene as a pretreatment for VPA have been used in the determination of VPA by GC or LC analysis. [1][2][3][4] Liquid chromatography-atmospheric pressure chemical ionization mass spectrometry (LC-APCI-MS) using a soft ionization technique facilitates drug metabolism. It is well known that the addition of ammonium acetate to the mobile phase increases the intensity of quasimolecule ion production by APCI technique.…”

mentioning

confidence: 99%

Determination of Valproic Acid in Serum by Liquid Chromatography–Atmospheric Pressure Chemical Ionization Mass Spectrometry

Mino¹,

Nakajima²,

Wakabayashi³

et al. 2001

ANAL. SCI.

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Valproic acid (VPA) is widely used in the treatment of epilepsy, particularly in the case of petit mal epilepsy. Free VPA is volatile and shows no characteristic absorption in the ultraviolet region (above 235 nm). Several derivatives of phenacyl, including trimethylsilyl (TMS), t-butyldimethylsilyl (t-BDMS) and 9-aminophenanthrene as a pretreatment for VPA have been used in the determination of VPA by GC or LC analysis. [1][2][3][4] Liquid chromatography-atmospheric pressure chemical ionization mass spectrometry (LC-APCI-MS) using a soft ionization technique facilitates drug metabolism. It is well known that the addition of ammonium acetate to the mobile phase increases the intensity of quasimolecule ion production by APCI technique. 5 LC-APCI-MS has been successfully applied for the determination of several non-and low polar materials.The present authors improved the sensitivity of VPA determination by increasing the ion intensity of VPA quasimolecule by LC-APCI-MS. This was achieved by adding ammonium acetate to the injection solution. The method was applied to the analysis of human serum extract dosed with VPA.In a previous work, we used LC-fluorometry 1 and GC-MS 6 for the determination of VPA. However, biological fluids contain complex matrices and each sample has to be pretreated using several cleaning techniques or has to be derivatized to identify the objective materials.We examined the usefulness of sensitive quantification of serum VPA by LC-APCI-MS technique without chemical modification of VPA and with ammonium acetate added to the injection solution. Experimental Chemicals and stock solutionsVPA was obtained from Tokyo Kasei Kogyo, Ltd. (Tokyo, Japan). All other chemicals were commercially available guaranteed reagents, and were used without further purification. All solvents were of HPLC grade and other chemicals were of analytical reagent grade. Distilled or deionized water was used for all experiments. Liquid chromatography-atmospheric pressure chemical ionization mass spectrometry (LC-APCI-MS)LC-MS analysis was performed on a Hitachi M 1000 LC-APCI mass spectrometer connected to a Hitachi L-6200 HPLC pump (Hitachi, Tokyo, Japan).To 20 µl of serum was added 0.48 µl of acetic acid-ammonium acetate buffer (pH 4.0) solution. The mixture was applied onto a solid phase column packed with 0.35 g of Extrelut packing materials, and allowed to stand for 20 min at room temperature. VPA was eluted from the Extrelut column with 12 ml of chloroform. To the eluate, 30 µl of 0.1 w/v% ammonium hydroxide in methanol was added, and the solution was mixed well. The mixtures were concentrated in vacuo at not more than 20˚C with a cooling trap. The concentrated residue was dissolved in 1.0 ml of 90% methanol: 0.1 mol/l acetic acid-ammonium acetate buffer (pH 4.0) (96:4, v/v) with vigorous stirring for 1 min, then filtered through a 0.4 µm membrane filter. Fifty microliters of the filtrate were directly injected onto LC-MS, which was interfaced with an APCI system. The chromatographic separation was performed using a...

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“…Although several procedures for acidic extraction have been described (Rettenmeier et al, 1989;Tatsuhara et al, 1987;Abbott et al, 1986, Kassahun et aE., 1989 1990), we have found extraction and derivatization under mild conditions preferable. Under acidic conditions 4-OH and 5-OH convert to their y-and 6-lactones, respectively, and 3-keto is decomposed to 3-heptanone.…”

Section: Resultsmentioning

confidence: 68%

“…Gas chromatography/mass spectrometry (GUMS) is therefore the chosen method because not only a host of VPA metabolites must be assayed, but these compounds must also be differentiated from endogenous compounds with related structures. Since our original GC/MS method was published in 1981 (Nau et al, 1981), a number of modified procedures have been developed (Rettenmeier et al, 1989;Tatsuhara et af., 1987;Abbott et al, 1986, Kassahun et d., 1989, 1990.…”

Section: Introductionmentioning

confidence: 99%

Quantitative determination of valproic acid and 14 metabolities in serum and urine by gas chromatography/mass spectrometry

Fisher

Wittfoht

Nau

1992

Biomedical Chromatography

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A method for the determination of the antiepileptic drug valproic acid and 14 of its metabolites in serum and urine by gas chromatography/mass spectrometry with selected ion monitoring of the trimethylsilylated derivatives has been developed. Sample preparation, including hydrolysis of VPA-conjugates and removal of urea in urine is carried out at pH 5.0 and is rapid and simple. The samples are extracted with ethyl acetate and the concentrated extracts are trimethylsilylated. Analysis with adequate separation of metabolites is achieved with a DB 1701 fused silica (Megabore) capillary column. The method exhibits high recovery and reproducibility and is sufficiently sensitive and selective for analysis of small sample volumes. Application of the method for screening patient serum and urine samples for unusual metabolite patterns, with possible predictive value for early detection of liver injury, is presented.

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Capillary gas chromatography-mass spectrometry of valproic acid metabolites in serum and urine using tert.-butyldimethylsilyl derivatives

Cited by 38 publications

References 15 publications

Valproate Metabolites in Serum and Urine During Antiepileptic Therapy in Children with Infantile Spasms: Abnormal Metabolite Pattern Associated with Reversible Hepatotoxicity

Valproate Metabolites in Serum and Urine During Antiepileptic Therapy in Children with Infantile Spasms: Abnormal Metabolite Pattern Associated with Reversible Hepatotoxicity

Determination of Valproic Acid in Serum by Liquid Chromatography–Atmospheric Pressure Chemical Ionization Mass Spectrometry

Quantitative determination of valproic acid and 14 metabolities in serum and urine by gas chromatography/mass spectrometry

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