The effect of gabapentin on antinociceptive action of analgesics.

The effect of gabapentin at a dose of 10 mg/kg (single administration) and at 3 mg/kg/day (administered for 10 days) on the analgesic action of morphine (10 mg/kg), metamizol (500 mg/kg) and indomethacin (10 mg/kg and 1.4 mg/kg) in mice was assessed on the basis of hot-plate and tail-flick tests. All the drugs were administered intraperitoneally (i.p.). Gabapentin was administered to mice 30 min before the administration of analgesics. The animals reactions to noxious stimuli were measured 60, 90 and 120 min after gabapentin administration. Gabapentin administered in a single dose, as well as in multiple ones, was found to cause antinociception, especially evident in the hot-plate test. The single dose of gabapentin enhances the analgesic effect of morphine in the hot-plate test, whereas in the tail-flick test it demonstrates an opposite effect. Gabapentin in a single dose does not affect significantly the effects of metamizol and indomethacin, whereas multiple doses decrease the action of these drugs. Gabapentin abolishes the tolerance of antinociceptive effect of morphine.