Background: Flunixin is a Non-Steroidal Anti-Inflammatory Drug (NSAID), because it can
effectively alleviate the organism of pyrexia, inflammation and pain, it has been widely used in veterinary
practice. In order to better study flunixin in the body's absorbed, distributed, metabolized and excreted,
our team developed a UPLC-MS/MS method for determination of flunixin in swine plasma,
urine and feces.
Methods: Flunixin was extracted from the sample by liquid-liquid extraction and cleaned-up using a
mixed-mode Oasis MCX solid-phase extraction column. Analysis was performed on UPLC-MS/MS
operating in Multiple Reaction Monitoring (MRM) mode. Internal standard was used for quantitation of
Results: Recoveries of fortified samples ranged from 90.2% to 101.4%, with Relative Standard Deviations
(RSD) lower than 17.0%. The Limits Of Detection (LODs) and Quantification (LOQs) in plasma
were 0.25 and 0.5 µg L-1, in urine were 0.25 and 0.5 µg L-1, and in feces were 0.5 and 1 µg kg-1, respectively.
This validated method was successfully applied to the determination of flunixin in real samples.
The half-life of flunixin after the last dose in pigs was 7.37±1.60 h after intramuscular administration of
2.2 mg/kg of flunixin, and approximately 6.8% and 1.9% of the administered dose was excreted as parent
compound in urine and feces respectively.
Conclusion: The developed UPLC-MS/MS method for determination of flunixin in swine plasma, urine
and feces was validated and successfully applied to monitor flunixin from real samples.