Abstract
A trial of the sedative effects of a novel benzodiazepine, climazolam, and of a mixture of climazolam and fentanyl–fluanisone was undertaken in male and female Sprague Dawley and Lewis strain rats (Rattus norvegicus) of different ages. At the recommended intravenous therapeutic dosage of 0·25 mg/kg, climazolam sedated the rats but failed to inhibit the righting reflex or responses to painful stimuli. Even at 25 times the recommended dosage, there was no anaesthetic effect. Predictable and satisfactory surgical anaesthesia was not obtained with the mixture of climazolam and fentanyl–fluanisone administered intraperitoneally. In contrast with diazepam and midazolam, climazolam failed to potentiate the sedative analgesic properties of fentanyl–fluanisone: indeed many animals retained their tail and pedal pinch reflexes. The results also revealed significant differences in effect related to strain and age but not to sex.