•This is the first study on quantifying vitacoxib in equine plasma.•This UPLC–MS/MS method with simple, rapid and sensitive was established.•The method was first successfully applied to a pharmacokinetic study after oral administrations of vitacoxib in horses.Vitacoxib is an imidazole derivative and the novel COX-2 selective inhibitor to be marketed for veterinary use as nonsteroidal anti-inflammatory drugs. No analytical assay to quantify vitacoxib in equine plasma samples has been published to date. In the current study, we aim to develop and validate a brief, quick and sensitive UPLC–MS/MS method for quantification of vitacoxib in equine plasma samples. Plasma samples were precipitated with methyl tert-butyl ether. The Phenomenex column (Kinetex 50 × 2.1 mm i.d. particle size = 2.6 μm, C18, 100 Å) at 25 °C was used in chromatographic separation with mobile phase consisting of acetonitrile and water (containing 0.1% formic acid) at flow rate of 0.4 mL/min. Vitacoxib and internal standard (IS, celecoxib) were detected under the multiple-reaction monitoring mode by mass spectrometer with ESI+ (m/z 347.9/269.03 for vitacoxib and m/z 382.0/362.0 for IS, respectively). The curve concentration range of was 0.5–500 ng/mL with a lower limit of quantification 0.5 ng/mL (r2 = 0.996309) in equine plasma samples. The selectivity, precision, recovery, accuracy, matrix effect and stability under various conditions were conformed to the acceptance requirements. Pharmacokinetic studies of vitacoxib in horses via oral administration (0.1 mg/kg) demonstrated that the procedure was fully validated and successfully. A meaningful basis for assessing the vitacoxib or clinical applications of vitacoxib to horse is provided in the present study.

Tiamulin is an antimicrobial widely used in veterinary practice to treat dysentery and pneumonia in pigs and poultry. However, knowledge about the metabolism of tiamulin is very limited in farm animals. To better understand the biotransformation of tiamulin, in the present study, in vitro and in vivo metabolites of tiamulin in rats, chickens, swine, goats, and cows were identified and elucidated using ultra-high performance liquid chromatography coupled to quadrupole/time-of-flight. As a result, a total of 26 metabolites of tiamulin, identified in vitro and in vivo, and majority of metabolites were revealed for the first time. In all farm animals, tiamulin undergoes phase I metabolic routes of hydroxylation in the mutilin part (the ring system), S-oxidation and N-deethylation on side chain, and no phase II metabolite was detected. Among these, 2β- and 8α-hydroxylation and N-deethylation were the main metabolic pathways of tiamulin in farm animals. In addition, we have put forward that 8a-hydroxy-tiamulin and 8a-hydroxy-N-deethyl-tiamulin could be hydroxylated into 8a-hydroxy-mutilin, the marker residue of tiamulin in swine. Furthermore, a significant interspecies difference was observed on the metabolism of tiamulin among various farm animals. The possible marker residues for tiamulin in swine were 8α-hydroxy-tiamulin, N-deethyl-tiamulin, and 8α-hydroxy-N-deethyl-tiamulin, which were consistent with the hypothesis proposed by the European Agency for the Evaluation of Medicinal Products. However, results in present study indicated that three metabolites (2β-hydroxy-tiamulin, N-deethyl-tiamulin, and 2β-hydroxy-N-deethyl-tiamulin) of tiamulin in chickens had larger yields, which implied that 2β-hydroxy-mutilin or N-deethyl-tiamulin was more likely to be regarded as the potential marker residue of tiamulin in chickens.Keywords: comparative metabolism; farm animals; in vivo; liver microsomes; tiamulin; UHPLC−Q/TOF;

•The dermal irritation and skin sensitization of a novel COX-2 inhibitor, vitacoxib, was assessed.•Vitacoxib did not induce dermal irritation in rabbits.•Vitacoxib did not show evidence of skin sensitization toxicity in guinea pigs.The prediction of side-effects is a key issue in the REACH initiative on chemicals in the preclinical testing of drugs. The dermal irritation and skin sensitization toxicity potential of a new molecule, vitacoxib, were invested in rabbits and guinea pigs in compliance with the Organization for Economic Cooperation and Development guideline. To assess dermal irritation, rabbits were dermally attached to vitacoxib for 72 h or repeated application. The results showed that no adverse reactions such as erythema and edema were observed throughout the test. In skin sensitization test, guinea pigs were sensitized to vitaoxib, positive and negative article for 24 h. No sensitization reaction was shown in the vitacoxib and negative group whereas severe sensitization was observed in the positive group. Based on these findings, vitacoxib does not cause dermal irritation and skin sensitization toxicity, and seems to be safe for animal use.Download high-res image (50KB)Download full-size image

Valnemulin, a semisynthetic pleuromutilin derivative related to tiamulin, is broadly used to treat bacterial diseases of animals. Despite its widespread use, metabolism in animals has not yet been fully investigated. To better understand valnemulin biotransformation, in this study, metabolites of valnemulinin in in vitro and in vivo rats, chickens, swines, goats, and cows were identified and elucidated using ultraperformance liquid chromatography–quadrupole/time-of-flight hybrid mass spectrometry (UPLC-Q/TOF-MS). As a result, there were totally 7 metabolites of valnemulin identified in vitro and 75, 61, and 74 metabolites detected in in vivo rats, chickens, and swines, respectively, and the majority of metabolites were reported for the first time. The main metabolic pathways of valnemulin were found to be hydroxylation in the mutilin part (the ring system) and the side chain, oxidization on the sulfur of the side chain to form S-oxides, hydrolysis of the amido bond, and acetylization in the amido of the side chain. In addition, hydroxylation in the mutilin part was proposed to be the primary metabolic route. Furthermore, the results revealed that 2β-hydroxyvalnemulin (V1) and 8α-hydroxyvalnemulin (V2) were the major metabolites for rats and swines and S-oxides (V6) in chickens.

•It was for the first time reported the toxicity of viacoxib as a new development compound coxibs of NSAIDs drug.•The acute and subacute oral toxicity were evaluated, respectively.•Significant pathological alterations were noted in kidneys and liver.•LD50 of vitacoxib was greater than 5000 mg/kg in SD rats and ICR mice mg/kg BW.•The NOAEL for sub-chronic toxicity of vitacoxib was considered to be 20 mg/kg bw/day for rats.Vitacoxib, is a newly developed coxibs NSAID (selective inhibitors of cyclooxygenase-2). To date, no experimental data have been published concerning its safety for use as an additive in the human diet. In the present study, we assessed the acute and sub-chronic toxicity of vitacoxib administered by gavage. The acute toxicity tests in Sprague Dawley (SD) rats and ICR mice demonstrated that vitacoxib at a dose of 5000 mg/kg BW failed to alter any of the parameters studied. In the 90-day sub-chronic toxicity test, vitacoxib was administered to SD rats at the doses of 0 (control), 5, 10, 20, 30, and 60 mg/kg BW. The results demonstrated that there were no significant differences for most indexes of sub-chronic toxicity throughout the experiment at the dose of 5–20 mg/kg BW, indicating no apparent dose-dependent. However, there were significant histopathology changes in the liver and kidney, and alterations in some biochemical parameters in the 60 mg/kg BW group. Based on these findings, the gavage LD50 was determined to be > 5000 mg/kg in SD rats and ICR mice, and the 90-day gavage no-observed-adverse-effect level (NOAEL) of vitacoxib was considered to be 20 mg/kg BW under the present study conditions.