Detection of flunixin in greyhound urine by a kinetic enzyme-linked immunosorbent assay

Abstract

A two-step kinetic enzyme-linked immunosorbent assay was developed to detect the presence of flunixin in the urine of greyhound dogs. The assay system was developed using polyclonal antiflunixin antisera, a rabbit albumin-flunixin conjugate adsorbed onto polystyrene microtiter strips, and flunixin reference standards for calibration. The assay parameters were optimized and the performance characteristics were determined. The quantitative intra- and inter-run precisions (%CV) of the analysis of replicate (n = 10) flunixin-spiked urine samples were 9.9-12.5% and 10.2- 13.6%, respectively. The linear dynamic range was 1-100 ng/mL, and the quantitative accuracy, as determined by calculation of percent error of measured flunixin in flunixin-spiked drug-free greyhound urine, was -16% to ±14% over this range. The 150 of the ELISA was 17.3 ng/mL. The limit of detection was 25 ng/mL in greyhound urine. The reactivity in the assay system relative to flunixin (100%) was 147% for flunixin glucuronide, 25% for clonixin, and 5% for niflumic acid. The ELISA was capable of detecting total flunixin for up to 72 h in dogs administered flunixin at 0.55 mg/kg orally and up to 96 h in a dog that was administered flunixin at 1.0 mg/kg orally.