Abstract

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Alfaxan® (Jurox Pty Ltd, Rutherford, NSW) is an injectable formulation of the neuroactive steroid anaesthetic drug alfaxalone (10 mg/mL). This investigation was designed to evaluate the efficacy and safety of Alfaxan® for induction of bitches prior to Caesarean section. The study was a prospective, multi-centre, positive-controlled, randomised efficacy study with two parallel groups: 1) Alfaxan® and, 2) Rapinovet X®--(propofol10 mg/mL). Animal Ethics Committee approval was obtained (No. JAEC/05/012).

A total of 74 bitches were induced intravenously to anaesthesia with 48 and 26 receiving Alfaxan® and Rapinovet X®, respectively. No premedicants were administered. All bitches were intubated and maintained on isoflurane and oxygen. Parameters were assessed prior to, during and after anaesthesia. The survival and vigour of pups delivered by Caesarean were also assessed. Parametric descriptive statistics, Student's T-tests, and linear or logistic regression were performed in Microsoft Excel or SAS for Windows, version 8.02 (SAS Institute Inc, Cary, NC, USA).

The average induction dose of Alfaxan® was 1.9 mg/kg body weight. Cardiovascular and respiratory parameters were well maintained during the induction, maintenance and recovery periods for both treatment groups. Immediate post induction apnoea occurred in 15% and 25% of Alfaxan® and Rapinovet X® cases, respectively. Anaesthetic induction was scored as: 1 (unacceptable), 2 (acceptable) or 3 (excellent). The average quality of anaesthesia was numerically superior during induction and anaesthesia with Alfaxan® compared to Rapinovet X®. Ninety-eight (98) and 81% of bitches scored a top score of 3 for induction and anaesthesia with Alfaxan®, respectively, while only 89 and 65% scored a 3 for the same parameters with Rapinovet X®. Anaesthetic recovery was scored as: 1 (poor), 2 (fair), 3 (good) and, 4 (excellent). Average scores for recovery were similar between the two treatment groups. No bitch fatalities were observed in this study. There were no statistically significant differences between treatment groups for the puppy variables; however, puppy vigour scores for Alfaxan® were numerically superior versus Rapinovet X®. Puppies born by Caesarean section to bitches having been administered Alfaxan® or Rapinovet X® had similar survival rates 24 hours after birth (i.e., 97 and 98%, respectively).

This study confirms the safety and efficacy of Alfaxan® for the purpose of anaesthetic induction for Caesarean section in the bitch.