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.

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.

Determination of methocarbamol in equine serum and urine by high-performance liquid chromatography with ultraviolet detection and atmospheric pressure ionization-mass spectrometric confirmation.

Urine and serum samples collected from four standard-bred mares after and oral regimen administration of methocarbamol were extracted and analyzed. The method consisted of enzyme hydrolysis followed by a one-step liquid-liquid extraction, separation on a reversed-phase (RP-18) column, and detection using an ultraviolet (UV) detector. The confirmation was carried out using a liquid chromatography-atmospheric pressure ionization-mass spectrometry (LC-API-MS) system. Maximum methocarbamol concentrations of 1498, 1734, 1547, 2322 micrograms/mL in urine and 4.9, 1.7, and 3.6 micrograms/mL in serum were observed. The peak concentrations of the drug were detected 1-4 h (urine) and 10-60 min (serum) after administration to four horses. The method validation results and drug elimination profiles for both urine and serum are presented and discussed.

Determination of triamcinolone acetonide in equine serum and urine by liquid chromatography-atmospheric pressure ionization mass spectrometry.

Urine and serum samples collected from four standard-bred mares after 30-mg intraarticular administrations of triamcinolone acetonide were analyzed using combined high-performance liquid chromatography-atmospheric pressure ionization mass spectrometry. Maximum triamcinolone acetonide concentrations of 32.3, 14.8, 24.3, and 29.4 ng/mL in the urine and 2.7, 1.9, 2.3, and 2.5 ng/mL in the serum samples were observed. The peak concentrations of the drug were detected approximately 22 h (urine) and 12 h (serum) after administration. The drug elimination profiles for both urine and serum are presented and discussed.

Investigation of the metabolism of azaperone in the horse.

Urine samples collected from a horse after intramuscular administration of 40 mg of azaperone were extracted at pH 10 before and after acid hydrolysis. The extracts were concentrated and analysed by LC-MS-MS. Two N-dealkylated metabolites, N-despyridinylazaperol and N-despyridinylazaperone, and a low concentration of azaperone were detected in the unhydrolysed urine. Six metabolites; hydroxyazaperol, two hydroxyazaperones, azaperol, N-despyridinylazaperol and N-despyridinylazaperone were detected in the hydrolysed urine extracts. Using XAD-2 resin extraction, three glucuronide conjugated azaperone metabolites (hydroxyazaperol glucuronide, hydroxyazaperone glucuronide and azaperol glucuronide) were detected in the urine. The mass spectra of these metabolites show the same characteristic daughter ions as the unconjugated metabolites. The glucuronide conjugated azaperone metabolites were partially hydrolysed in the heated nebulizer interface to the unconjugated metabolites.