Comparison of the Analgesic Activity of Antiparkinsonian Aminoadamantane Derivatives Amantadine and Hemantane

The efficacy of some aminoadamantane derivatives used as neurodegeneration treatments is due to their ability to block NMDA receptors. But this mechanism of pharmacological action can also produce analgesic activity. Analgesic properties of two aminoadamantanes, amantadine (20 mg/kg) and hemantane (20 mg/kg), which were uncompetitive NMDA receptor antagonists, were assessed in rodent models of pain induced by different pain stimuli (tail-flick test, acetic twitches test in mice and formalin test in rats). Additionally, the anti-inflammatory properties of hemantane and amantadine were evaluated in mice with acetic peritonitis and in rats with hind paw edema induced by formalin injection. The results of our study demonstrate that the analgesic activity of the 1-aminoadamantane amantadine differs from the 2-aminoadamantane hemantane. The analgesic activity of amantadine administered intraperitoneally was more pronounced in the case of acute thermal pain in mice compared to hemantane, and only amantadine had a significant analgesic effect on the acute early phase of formalin pain in rats induced by the effect of the algogen on the primary sensory afferents. Hemantane was more effective than amantadine for relieving pain produced by inflammation owing to its pronounced anti-inflammatory activity: only hemantane decreased the amount of acetic twitches in mice that received drugs orally and was effective in the tonic phase of formalin pain in rats.