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.

The research article presents a method for detecting a drug known as etodolac in horses’ urine and serum, using high-performance liquid chromatography and atmospheric pressure ionization mass spectrometry. It also discusses the times and concentrations at which peak drug effects occur, the duration of its detectability, and shows that etodolac is converted into monohydroxylated etodolac in the body.

Method for Detection of Etodolac

• The researchers used a high-performance liquid chromatographic method for detecting etodolac in equine serum and urine.
• This method involves a one-step liquid-liquid extraction, separation on a reversed-phase column and detection using an ultraviolet detector.
• For additional confirmation, the high-performance liquid chromatography method was paired with an atmospheric pressure chemical ionization mass spectrometer.

Concentration and Detection Time of Etodolac

• The scientists administered Ultradol, a drug containing etodolac, orally to four standardbred mares.
• The concentration of etodolac in the urine and serum samples was measured and tracked over time.
• Maximum etodolac concentrations were between 568 and 767 micrograms per milliliter (μg/mL) in urine and between 2.2 and 4.1 μg/mL in serum.
• Peak concentrations were detected within 2 to 10 hours in urine and within 40 minutes to 6 hours in serum, post-administration.
• Etodolac was detectable up to 79 hours in urine and up to 48 hours in serum post-administration.

Method Ruggedness and Stability Studies

• The study also included a ruggedness and precision study of the methods used to detect etodolac in serum and urine.
• These findings discuss the method’s reliability and dependability for its intended use, an essential component in its validity and potential for wider adoption.

Identification of Metabolites

• Finally, the researchers identified three main metabolites of etodolac from the horse urine via liquid chromatography-APCI-MS.
• All three metabolites were identified as monohydroxylated etodolac, offering insights into how the drug is processed within the equine body.