Two hundred and twelve dogs were treated either intravenously or intramuscularly with either dexmedetomidine or medetomidine in a randomised double-blinded multicentre clinical study during procedures such as dental care, radiography and otitis treatment. Sedative, analgesic and cardiorespiratory parameters and body temperature were assessed for three hours after the treatments. Approximately half the dogs were given atipamezole intramuscularly after the completion of the procedure, and the other dogs were allowed to recover spontaneously. Dexmedetomidine and medetomidine induced similar clinical effects, and the procedure was completed successfully in 97 per cent of cases. There were few adverse side effects, but they included prolonged sedation, hypothermia, apnoea and bradycardia; no adverse effects were observed after the administration of atipamezole, which effectively reversed all the clinical effects of dexmedetomidine and medetomidine.