Rocuronium is a non‐depolarising neuromuscular block drug extensively used in canine patients due to its favourable characteristics, including the fastest onset of action among all non‐depolarising neuromuscular blocking agents, lack of active metabolites and intermediate duration of effect. Although rocuronium elimination is relatively independent of kidney function, in the past few years, a growing number of reports describing a prolonged duration of the effect of rocuronium in human patients with renal failure have been published. However, to date, the mechanism behind this phenomenon is unclear. The present case describes the development of extremely prolonged neuromuscular blockade (>5 hours) following a single dose of 0.5 mg/kg rocuronium in a female English bulldog with renal disease where neostigmine failed to provide adequate reversal, which was only subsequently achieved following administration of sugammadex. Aside from renal disease, other possible causes of this prolonged duration (relative drug overdose, hypoalbuminaemia, co‐administered drugs, neostigmine‐induced neuromuscular blockade and idiosyncratic reaction to rocuronium) are also discussed.

To assess stability and degradation over time, of methadone alone, and mixed with lidocaine and ketamine, using various diluents and storage conditions.Materials and MethOds: Solutions of methadone diluted in 0.9% NaCl, and methadone-lidocaineketamine diluted in 0.9% NaCl or Hartmann's solution, and stored at room temperature with exposure to light, or refrigerated at 4°C and protected from light, were maintained over 10 days. Chemical stability was determined using liquid chromatography immediately after preparation and following 4, 24, 48, 96 and 240 hours of storage. Physical stability of the solutions was evaluated by visual examination and absorbance of ultraviolet/visible light. A linear model assessed the impact of different diluent solutions and storage conditions on drug degradation over time.results: There was no evidence of physicochemical incompatibility for any solution. Methadone concentration, when diluted alone or in methadone-lidocaine-ketamine with Hartmann's solution at 4°C, did not decline over time. Ketamine and lidocaine decreased to a similar extent over time, regardless of the diluent used or storage method, while methadone in methadone-lidocaine-ketamine diluted with 0.9% NaCl or with Hartmann's solution at room temperature exposed to light, also declined over time; however, all three methadone-lidocaine-ketamine components retained acceptable stability (<10% degradation) for at least 48 hours following preparation, irrespective of diluent or storage conditions. clinical significance: Regardless of the diluent or storage method, methadone-lidocaine-ketamine solutions degrade over time, but this only becomes clinically significant after 48 hours. Solutions of 1 mg/ml methadone in 0.9% NaCl are stable for at least 10 days under storage conditions likely to be encountered in general practice.