Determination of carprofen in blood by gas chromatography chemical ionization mass spectrometry

Abstract

A gas chromatographic chemical ionization mass spectrometric assay has been developed to measure carprofen in blood. The method features the addition of either a structural or stable isotope analog internal standard to plasma prior to a simple benzene extraction at pH 4.5. The residue, after removal of the benzene, is methylated with ethereal diazomethane. Following evaporation of the methylating solvents, a portion of the reconstituted residue is analyzed by gas chromatography mass spectrometry. The mass spectrometer is set to monitor in the gas chromatographic effluent the [MH]+ ions of carprofen methyl ester and the methyl ester of the internal standard generated by isobutane chemical ionization. Assay sensitivity is 5 pmol ml-1. When 200 pmol ml-1 samples are analyzed using a stable isotope analog as the internal standard, the precision and accuracy are both 4%. Using a structural analog as the internal standard, the assay was neither as precise nor as accurate.

Preliminary study on carprofen concentration measurements after transcutaneous treatment with Vetdrop® in a microfracture joint defect model in sheep

“…The intravenously treated animals showed an interval peak plasma concentration, as described in a previous study [ 17 ] in sheep. The concentration was highest 10 minutes after the iv.…”

“…Carprofen is a commonly used NSAID in veterinary medicine and was thus considered an ideal study material for the purposes of the current study. It has strong analgesic, antipyretic and antiphlogistic effects [ 17 – 19 ], although the exact mechanism of action of carprofen is not yet clear [ 20 ]. In vitro assays performed, using canine and equine chondrocytes demonstrated carprofen as having an inhibitory effect on prostaglandin-E2-synthesis [ 15 , 21 ].…”