The reports of analgesic effects of benzodiazepines are inconsistent. There is evidence of a hyperalgesic effect induced by activation of supraspinal GABAA receptors and an antinociceptive effect induced by activation of receptors located in the spinal cord (dorsal horns). The aim of the study was to discover whether the systemic administration of a benzodiazepine agent alprazolam increases the systemic analgesic efficacy of non-opioid analgesic ibuprofen. Experimental studies combining these agents have not yet been published. We used three experimental methods - writhing test (with acetic acid), tail-flick test and plantar test to assess analgesic action. The drugs were administered orally. Augmentation of the analgesic effect of ibuprofen by alprazolam was proved for the writhing test at a dose of 30 mg/kg of ibuprofen and alprazolam 1 mg/kg. The reaction time of the combination was significantly prolonged in comparison with ibuprofen alone. The results of the tail-flick test and plantar test were negative. The effect of ibuprofen was not enhanced by alprazolam in tests of acute thermal pain. Our results have demonstrated that the analgesic action of ibuprofen is only weakly enhanced by alprazolam.

Department of Pharmacology 3rd Faculty of Medicine Charles University Prague Czech Republic