64 patients with severe chronic periodontitis were divided into 2 groups(n =32)randomly.Intramuscular injection of ketorolac tromethamine(KT group)and local block injection of lidocaine(L group)were respectively applied for periodontal subgingival scaling and root planning.The analgesic effect was assessed using VAS,the adverse drug reactions were recorded during and after operation.During op-eration the VAS between the 2 groups was not statistically different(P >0.05).6 and 1 2 h after operation the VAS of KT group was lower than that of L group(P <0.05).During operation minor intraoperative local adverse reactions were observed in all cases in L group,but not any in KT group(P <0.05);after operation minor adverse reactions were observed in 1 case of KT group and in 2 cases of L group(P >0. 05).