Propofol & Benzyl Alcohol: Safe for Cats, so Far
Propofol is formulated for anesthetic use in a lipid-based oil-in-water emulsion. A new formulation containing the original lipid emulsion with 2% benzyl alcohol has been introduced to the market to allow opened vials to be retained for a longer time. As cats are vulnerable to benzyl alcohol toxicity, a study was conducted evaluating the potential toxicity in cats administered a propofol emulsion containing the preservative. Preliminary data concluded the presence of 2% benzyl alcohol in the formulation of propofol did not cause significant morbidity and mortality under excessive and repeat dose conditions in cats. For the main study, 8 cats were administered 1% propofol containing 2% benzyl alcohol (PB); 8 cats were administered preservative-free propofol as a control (PC). Cats were anesthetized with propofol (8 mg/kg) 3 times at 48-hour intervals in phase 1. The cats underwent 3 anesthetic procedures at 48-hour intervals in phase 2, with anesthesia maintained until 24 mg/kg had been administered. Regular hematological and biochemical analyses and clinical examinations were performed; cardiorespiratory function was monitored throughout anesthesia. Neurological examinations were performed daily for 7 days following phase 2. Cats were euthanized 7 days after phase 2 and postmortem examinations performed to assess organ toxicity. No clinically relevant differences between PB and PC were detected. The study revealed no additional effect when benzyl alcohol is added to propofol and is used at normal-to-high clinical doses in healthy cats.
CommentaryThe original formulations of propofol lacked preservatives, necessitating disposal within hours even after a single use. A propofol product that contains 2% benzyl alcohol as a preservative allows for multiple uses for up to 28 days (PropoFlo; abbott.com). Concerns regarding this new formulation are based on documented potential adverse effects of benzyl alcohol on feline blood and nervous systems. Based on the results of this study, propofol-containing benzyl alcohol (up to 48 mg/kg over 45 min–120 min) can be used safely in clinically healthy cats without the concern of long-term blood or nervous system side effects.—Andrew Claude, DVM, DACVA
SourceEvaluation of propofol containing 2% benzyl alcohol preservative in cats. Taylor PM, Chengelis CP, Miller WR, et al. J FELINE MED SURG 14:516-526, 2012.