The aim of this study was to assess the influence of ketorolac tromethamine and dexamethasone on substance P and IL-8 expression when used as a root canal irrigant for single visit root canal treatment for acute irreversible pulpitis. A total of 42 patients with pain due to acute irreversible pulpitis in carious premolar and molar teeth were included in this study. The four irrigation groups were as follows: saline (n = 11), 3% sodium hypochlorite (n = 11), ketorolac tromethamine (n = 10) and dexamethasone (n = 10). Blood samples S1 and S2 were collected upon access opening and after canal preparation, respectively. Quantification of substance P and IL-8 were done using ELISA test. Post-operative pain was assessed by questioning the patients. The difference between S1 and S2 sample values for the four different irrigant groups was not significant. The sodium hypochlorite group had a higher mean expression of substance P and IL-8 values. Dexamethasone irrigation was more effective in controlling post-operative pain.