Synergistic interaction of pregabalin with the synthetic cannabinoid WIN 55,212-2 mesylate in the hot-plate test in mice: an isobolographic analysis.

BACKGROUND The aim of the study was to determine the type of interaction between pregabalin (a 3(rd)-generation antiepileptic drug) and WIN 55,212-2 mesylate (WIN - a highly potent non-selective cannabinoid CB1 and CB2 receptor agonist) administered in combination at a fixed ratio of 1:1, in the acute thermal pain model (hot-plate test) in mice. METHODS Linear regression analysis was used to evaluate the dose-response relationships between logarithms of drug doses and their resultant maximum possible antinociceptive effects in the mouse hot-plate test. From linear equations, doses were calculated that increased the antinociceptive effect by 30% (ED(30) values) for pregabalin, WIN, and their combination. The type of interaction between pregabalin and WIN was assessed using the isobolographic analysis. RESULTS Results indicated that both compounds produced a definite antinociceptive effect, and the experimentally-derived ED(30) values for pregabalin and WIN, when applied alone, were 29.4 mg/kg and 10.5 mg/kg, respectively. With isobolography, the experimentally derived ED(30 mix) value for the fixed ratio combination of 1:1 was 5.7 mg/kg, and differed significantly from the theoretically calculated ED(30 add) value of 19.95 mg/kg (p < 0.01), indicating synergistic interaction between pregabalin and WIN in the hot-plate test in mice. CONCLUSIONS Isobolographic analysis demonstrated that the combination of WIN with pregabalin at a fixed ratio of 1:1 exerted synergistic interaction in the mouse model of acute thermal pain. If the results from this study could be adapted to clinical settings, the combination of WIN with pregabalin might be beneficial for pain relief in humans.