Antinociceptive activity of Eupatorium buniifolium aqueous extract.

The antinociceptive properties of the aqueous extract of Eupatorium buniifolium aerial parts were investigated in chemical and thermal models of nociception in mice. Oral doses of 250 and 500 mg/kg produced an inhibition of 42.3% and 73.9%, respectively, of the abdominal writhes induced by acetic acid in mice. This antinociceptive effect was not reversed by pretreatment with naloxone. In the formalin test, the administration of 500 and 1000 mg/kg p.o. had no effects in the first phase (0-5 min) but produced a dose-dependent analgesic effect on the second phase (15-30 min) with inhibitions of the licking time of 38.9% and 57.3%, respectively. In the hot plate test, no effect was seen at the dose of 500 mg/kg p.o.