Antinociceptive Effect of Promethazine in Mice

The present study was undertaken to investigate the nociception activity of promethazine, a tranquillizer devoid of hypnotic activity in mice.Antinociception was evaluated, using the acetic acid-induced writhing, tail flick, hot plate and formalin pain tests.Promethazine (4 and 6 mg/kg) and acetylsalicylic acid (100 mg/kg) produced a significant inhibition of the second phase response in the formalin pain model (P<0.05) and the drug couldn’t show an antinociceptive effect in the first phase. Morphine (10 mg/kg) inhibited both first and second phase response (P<0.01). Drug also showed a dose-dependent inhibition of acetic acid-induced abdominal writhes. The tail flick and hot plate latency weren’t different from control (P>0.05) and administration of naloxone (0.1 mg/kg) couldn''t block the antinociceptive effect of promethazine.The data obtained suggest that antinociceptive effects of the promethazine may be mediated via peripheral and not central mechanisms.