title: Determination of pivaloylcarnitine in human plasma and urine by high-performance liquid chromatography with fluorescence detection.
abstract: A high-performance liquid chromatographic (HPLC) method was developed for the determination of pivaloylcarnitine, one of the major metabolites of pivaloyloxymethyl (+)-(6R,7R)-7-[(Z)-2-(2-amino-4-thiazolyl)-2- pentenamido]-3-carbamoyloxymethyl-8-oxo-5-thia-1-azabicyclo[4.2.0] oct-2- ene-2-carboxylate hydrochloride hydrate (S-1108), an oral cephem antibiotic, in human plasma and urine. Fluorescence detection was done with 3-bromomethyl-6,7-dimethoxy-1-methyl-2(1H)-quinoxalinone as the labeling reagent. Pivaloylcarnitine and cyclopropylacetylcarnitine, the internal standard, were selectively fractionated from plasma or urine on a disposable cation-exchange column. Derivatization was completed in 20 min at 40 degrees C in the presence of N,N'-diisopropylethylamine as the catalyst. A column-switching device was used to remove the excess reagent for HPLC analysis. The recovery of pivaloylcarnitine was greater than 98%, and average within-day and between-day coefficients of variation were less than 5% at concentration ranges of 0.05-2 micrograms/mL for plasma and 5-500 micrograms/mL for urine. Detection limits were 0.02 micrograms/mL for plasma and 1 micrograms/mL for urine. The urinary recovery of pivaloylcarnitine was 94% after the administration of S-1108, a result that suggested that S-1108 was almost quantitatively converted to pivalic acid and then conjugated with carnitine.
authors.affiliation: Shionogi Research Laboratories, Shionogi & Company, Ltd., Osaka, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Konishi
authors.forename: H
authors.initials: H
authors.lastname: Hashimoto
mesh_terms: D002138:Calibration; D002331:Carnitine / Q000031:analogs & derivatives* / Q000097:blood / Q000652:urine; D002511:Cephalosporins / Q000008:administration & dosage; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004355:Drug Stability; D006801:Humans; D010421:Pentanoic Acids / Q000378:metabolism; D011355:Prodrugs / Q000008:administration & dosage; D011810:Quinoxalines; D012680:Sensitivity and Specificity; D013050:Spectrometry, Fluorescence
chemical_list: D002511:Cephalosporins; D010421:Pentanoic Acids; D011355:Prodrugs; D011810:Quinoxalines; C052465:3-bromomethyl-6,7-dimethoxy-1-methyl-2(1H)-quinoxalinone; C076133:S 1108; C005566:pivalic acid; C054040:pivaloylcarnitine; D002331:Carnitine