Comparing the analgesic effect of hydroalcoholic extract of green tea and sodium salicylate in the formalin test in rats

Background: Green tea is believed to have some health promoting benefits. Among them anti-inflammatory properties are proposed to cause an analgesic effect. Few studies also have given it a central role to inhibit pain. The aim of this experiment was to compare the anti-nociception effects of green tea extract and sodium salicylate on neurogenic and inflammatory pain induced by formalin injection.Methods: The experiment was done on ۳۱ male Wistar rats. They were randomly divided into four groups: normal saline treated (control), sodium salicylate treated and the other two groups were treated with different dosages of green tea extracts (۲۰۰ and ۳۰۰ mg/kg) intra-peritoneally. All subjects underwent the standard formalin test ۳۰ minutes after the treatments and were followed for ۶۰ minutes.Results: In the early and the intermediate phases of the study, treatment with ۲۰۰ mg/kg (p=۰.۰۱ for early phase; p = ۰.۰۲ for intermediate phase) and ۳۰۰ mg/kg (p = ۰.۰۲ for intermediate phases) of green tea extract demonstrated lower levels of pain in comparison with sodium salicylate but not with the control group (p > ۰.۰۵). In the late phase of the test, the control group had significantly higher nociception scores than the other groups (P = ۰.۰۱۸ for green tea ۲۰۰ mg/kg, P = ۰.۰۳۸ green tea ۳۰۰ mg/kg, and p = ۰.۰۱۶ for sodium salicylate). The green tea treated groups and those treated with sodium salicylate showed similar nociception scores in the late phase of formalin test (p > ۰.۰۵).Conclusion:Green tea extract administration seems to be effective against painful feelings at least in an inflammatory condition. This effect of green tea is comparable with sodium Salicylate. This finding is such a confirmatory data according to other investigations and might be clues to utilize proven safer analgesics.