“…This class of drugs is arguably the most commonly used medications in equine medicine, with phenylbutazone (PBZ) and flunixin meglumine (FM) being among the most frequently administered of the group. While the in vivo metabolism and pharmacokinetics of both drugs in horses have been extensively described (Gerring, Lees, & Taylor, 1981; Knych, Arthur, Mckemie, & Chapman, 2015; Knych, Arthur, et al, 2019; Knych, Baden, Gretler, & McKemie, 2019; Knych, Stanley, Seminoff, McKemie, & Kass, 2016; Lees, Landoni, Giraudel, & Touitain, 2004; Lees, Ewins, Taylor, & Sedgwick, 1987; Lees, Taylor, Maitho, Millar, & Higgins, 1987; Sams, Gerken, & Ashcraft, 1999; Semrad, Sams, Harris, & Ashcraft, 1993), to date, there are no published reports describing the in vitro metabolism of these compounds in horses. While these drugs undergo significant metabolism and only small amounts of parent compound are found in the urine, pharmacokinetic parameters reportedly vary greatly between individual animals (Knych et al., 2015, 2016; Knych, Arthur, et al, 2019; Knych, Baden, et al, 2019).…”