The antinociceptive effect of hydro-alcoholic extract of leave Mentha pulegium in formalin test in male rat

Drug researchers believe that pain relief medicines, because of their side effects and in some cases because of their inabilities are not useful. Therefore, it is necessary to do more research to find out new antinociceptive drugs. In the present study, antinociceptive effect of hydro-alcoholic extract of Mentha pulegium leave has been evaluated in male rats. In this experimental study, 40 adult male wistar rats, in the weight range of 220- 230 g were used. Antinociceptive response was evaluated by formalin test in five groups of 8 animals. Three experimental groups received 3 different doses of hydro alcoholic extract from the leaves of Mentha pulegium (400, 800, 1600 mg/kg, respectively). Sham group received distilled water and formalin only and the control group received no drugs. The extracts were injected intraperitoneally (i.p.), 15 minutes before the formalin test. Minutes 0-5 and 15-60 were designated as the acute and chronic phase of pain, respectively. After recording behavioral responses, the average pain scores in experimental groups and control group were statistically evaluated using t-test and Tukey’s test. A significant difference was seen in mean pain scores between 3 experimental groups in the acute stage of formalin test. In the chronic stage, the only significant difference was seen between the experimental group which had been received 1600 mg/kg Mentha pulegium and two other groups (sham and control group) (P<0.05). According to the results of this research, the hydro-alcoholic extract of the leaves of Mentha pulegium reduces the pain in the acute stage more than chronic stage. However, more research is needed to find out the effective antinociceptive compounds in Mentha pulegium.