Etodolac in equine urine and serum: determination by high-performance liquid chromatography with ultraviolet detection, confirmation, and metabolite identification by atmospheric pressure ionization mass spectrometry.

摘要

A high-performance liquid chromatographic method was used for the detection of etodolac in equine serum and urine. The method consisted of a one-step liquid-liquid extraction, separation on a reversed-phase (RP-18) column and detection using an ultraviolet detector. Additional confirmation methods included a HPLC coupled with an atmospheric pressure chemical ionization mass spectrometer (APCI-MS). Free (unbound) etodolac and its conjugates were present in the samples. Concentrations of the drug in the serum and urine samples collected from four standardbred mares after a single oral administration of Ultradol were determined. Maximum etodolac concentrations of 712, 716, 568, and 767 microg/mL in urine and 4.1, 3.6, 3.1, and 2.2 microg/mL in serum were observed. The peak concentrations of the drug were detected 2-10 h (urine) and 40 min-6 h (serum) after administration to four horses. The maximum detection time was 79 h in urine and 48 h in serum after the drug administration. The drug-elimination profiles for both urine and serum are presented and discussed. Method ruggedness and precision and stability studies of etodolac in serum and urine are presented. Three major metabolites were detected in the urine by liquid chromatography-APCI-MS. All three metabolites were identified as monohydroxylated etodolac.