European journal of pharmacology
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Flupirtine is a novel analgesic recently introduced with therapy. The present study assessed the role of opioid mechanisms in flupirtine-induced antinociception, localized its site of action along the neuraxis and evaluated its relative potency. Analgesic and general behavioral effects of flupirtine (0.3-10 mg/kg i.v.) were compared to those of the opioid analgesic pentazocine (0.3-5 mg/kg i.v.) in chronic spinal dogs. ⋯ Both drugs constricted pupils and lowered body temperature. In drug interaction studies, a relatively high dose (1 mg/kg i.v.) of the opioid antagonist naltrexone antagonized the effects of pentazocine but not those of flupirtine. It is concluded that flupirtine-induced antinociception is not opiate-receptor mediated, that its antinociceptive actions occur primarily at supraspinal sites and that its potency is less than that of pentazocine in the dog.