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The pharmacokinetics of cefquinome were studied in healthy and Pasteurella multocida-infected rabbits after a single intramuscular (IM) injection at 2 mg/kg of its sulfate salt. Twelve female New Zealand white rabbits (2.0-2.5 kg) were used; six of them served as controls, and the other six had been infected with P. multocida; the experiments were conducted 1-2 days after nasal inoculation of P. multocida when rabbits showed the signs of respiratory infection. Plasma concentrations of cefquinome were determined using high-performance liquid chromatography. The values of elimination half-life, area under the curve, area under the first moment curve, and mean residence time were significantly lower in infected rabbits (0.48 hr, 4.54 hr*μg/ml, 3.63 hr* hr*μg/ml and 0.8 hr, respectively) than healthy rabbits (0.72 hr, 9.11 hr*μg/ml, 9.85 hr* hr*μg/ml and 1.1 hr, respectively), whereas total body clearance was significantly higher in infected than healthy rabbits. Therefore, P. multocida infection caused significant changes in some of the pharmacokinetic parameters of cefquinome in rabbits. These pharmacokinetic changes may affect dose regimen when used in P. multocida-infected rabbits., (© 2018 John Wiley & Sons Ltd.)

Pupillary response to xylazine (10-300 micrograms/kg, i.v.) norepinephrine (1-30 micrograms/kg. i.v.) and atropine (3-100 micrograms/kg, i.v.) were observed in rats anaesthetized with pentobarbital. Xylazine caused a dose-dependent mydriasis which was antagonized by a selective alpha 2-adrenergic blocking agent, yohimbine (2.5 mg/kg, i.v.). was less effective in antagonizing this effect of xylazine. A selective alpha 1-adrenergic blocking agent, prazosin (2.5 mg/kg, i.v.) was ineffective in reducing the xylazine-induced mydriasis. In contrast, both phentolamine and prazosin blocked the pupillary dilation produced by norepinephrine, while yohimbine was much less effective in antagonizing norepinephrine-induced mydriasis. Atropine also induced a dose-dependent mydriasis which was not affected by yohimbine pretreatment. The present study suggests that the mydriatic effect of xylazine in the rat is mediated by an adrenergic mechanism, possibly by stimulating the alpha 2-adrenergic receptors in the iris and CNS.