RESEARCH PAPER A comparison of propofol, thiopental or ketamine as induction agents in goats Nikitas N Prassinos* DVM, PhD, Apostolos D Galatos* DVM, PhD, Diplomate ECVA & Dimitris Raptopoulos DVM, DrMedVet, DVA, Diplomate ECVA *Clinic of Surgery, Faculty of Veterinary Medicine, University of Thessaly, Greece  Clinic of Surgery, Faculty of Veterinary Medicine, Aristotle University of Thessaloniki, Greece Correspondence: Nikitas N. Prassinos, Clinic of Surgery, Faculty of Veterinary Medicine, University of Thessaly, Trikalon 224, PO Box 199, GR-43100 Karditsa, Greece. E-mail: ngreen@vet.uth.gr Abstract Objective To compare propofol, thiopental and ketamine as induction agents before halothane anaesthesia in goats. Study design Prospective, randomized cross-over study. Animals Seven healthy adult female goats with mean (±SD; range) body mass of 38.9 ± 3.29 kg; 35–45 kg. Methods The seven animals were used on 21 occasions. Each received all three anaesthetics in a randomized cross-over design, with an interval of at least 2 weeks before re-use. Anaesthesia was induced with intravenous (IV) propofol (3 mg kg )1 ), thiopental (8 mg kg )1 , IV) or keta- mine (10 mg kg )1 , IV). Following tracheal intuba- tion, anaesthesia was maintained with halothane for 30 minutes. Indirect blood pressure, heart rate, respiratory rate and arterial blood gases were monitored. The quality of induction and recovery, recovery times and incidence of side-effects were recorded. Results Induction of anaesthesia was smooth and uneventful, and tracheal intubation was easily performed in all but two goats receiving ketamine. Changes in cardiopulmonary variables and acid– base status were similar with all three induction agents and were within clinically acceptable limits. Mean recovery times (time to recovery of swallow- ing reflex and to standing) were significantly shor- ter, and side-effects, e.g. apnoea, regurgitation, hypersalivation and tympany, were less common in goats receiving propofol, compared with the other treatments. Conclusions and clinical relevance Propofol 3 mg kg )1 IV is superior to thiopental and ketamine as an induction agent before halothane anaesthesia in goats. It provides uneventful recovery which is more rapid than thiopental or ketamine, so reduces anaesthetic risk. Keywords anaesthesia, goat, ketamine, propofol, thiopental. Introduction Thiopental and ketamine are popular anaesthetics in small ruminants (Gray & McDonell 1986; Riebold 1996) while propofol has been used extensively in animals and human beings. Pharmacokinetic stud- ies in various species have revealed that propofol has a high volume of distribution, rapid metabolism and rapid clearance when given by repeated doses or continuous intravenous (IV) infusion (Langley & Heel 1988; Nolan & Reid 1991; Nolan et al. 1991; Reid et al. 1993; Hall et al. 1994; 289 Veterinary Anaesthesia and Analgesia, 2005, 32, 289–296