© 2015 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia. Objective: To compare the sedative effects of an intramuscular (IM) low dose of medetomidine in combination with butorphanol or methadone in dogs. Study design: Prospective, blinded, randomized clinical trial. Animals: Forty-eight healthy adult dogs that required sedation for diagnostic or surgical elective procedures. Methods: Dogs were sedated IM with medetomidine (2.5 μg kg-1) and either butorphanol (0.4 mg kg-1) or methadone (0.4 mg kg-1). The degree of sedation was assessed every 10 minutes, for 30 minutes, using a numeric descriptive scale. Data on heart rate (HR), respiratory rate, capillary refill time, temperature and response to a toe pinch were recorded. The response to venous catheterization at minute 30 was also evaluated. Results: Both combinations produced moderate to deep sedation with a maximal effect at 20-30 minutes without significant differences in the degree of sedation between the treatments at any studied time-point. HR decreased from minute 10 to minute 30 with both opioid combinations (p < 0.05); this reduction did not differ between groups (p > 0.05). No differences between groups were detected in any of the other variables. Conclusions and clinical relevance: Combinations of a low dose of medetomidine with butorphanol or methadone, respectively, provide similar degrees of sedation.