Antinociceptive activity of methanolic extract of Epilobium hirsutum

Antinociceptive activity of methanolic extract of aerial parts of Epilobium hirsutum (EH) was determined in the Hot plate and writhing tests in mice. Nearly all extracts showed a dose dependent and marked analgesic activity in mice in the thermal and chemical models of analgesia when compared to the control. Methanol extract at dose of 500 mg kg(-1) showed higher activity (97.7% writhing inhibition) than diclofenac 50 mg kg(-1) i.p., (77.8%, p<0.05) and morphine 5 mg kg(-1) i.p. (91.2%, p<0.05). Methanol extract, in all tested doses (200-500 mg kg(-1)) significantly increased the pain threshold in hot plate test (p<0.05). EH extract at 200 mg kg(-1) showed a similar effect to morphine at 5 mg kg(-1). These finding indicate the potential therapeutic use of methanolic extract of aerial parts of EH as a potent antinociceptive agent. LD50 was obtained 1.5+/-0.1 g kg(-1). EH extract did not induce locomotor impairment in mice at any tested doses.