Aims: Considering the numerous side effects of common analgesic drugs, finding proper analgesic drugs is important. The Scrophularia is a plant that contains appropriate anti-inflammatory compounds. In this study the analgesic effect of diclofenac drug and ethanolic extract made of aerial parts of Scrophularia Megalanta was studied in male rats by formalin inflammatory model.

Methods: Using 48 male rats and applying the formalin test pain model, the pain behavior was examined by intraperitoneal injection of 25, 50, 100 and 200mg/kg concentrations of extract in four treatment groups with diclofenac and control groups. Observation of pain behavior was done for each 15 seconds and total of 60 minutes after the formalin injection and the collected data was calculated for each rat averagely. The findings of different groups of the test at two acute and chronic stages was separately analyzed using one-way ANOVA and Tukey tests using SPSS 15 software.

Results: Both acute and chronic phases of pain resulting from the formalin injection were observed in all groups. In the acute phase, administration of 50mg (p<0.05), 100mg (p<0.01) and 200mg (p<0.001) doses of Scrophularia Megalanta extract decreased the symptoms of pain compared with the control group. Likewise, in the chronic phase, administration of the extract in all used doses caused a significant reduction in pain compared to the control group, especially at minutes 15-40 of the test which was greater in doses of 100 and 200mg.

Conclusion: Peripheral injection of the ethanolic extracts of Scrophularia Megalanta has central and peripheral anti-analgesic effect.