ObjectiveTo evaluate the effects of parecoxib on efficacy of patient-controlled epidural analgesia(PCEA) with different doses of morphine after cesarean section.MethodsThree hundred ASA Ⅰ or Ⅱ parturients at full term aged 20-40 yr weighing 54-89 kg undergoing elective cesarean section were randomly divided into 3 morphine groups-regular,median and small dose (groups Ⅰ,Ⅱ[ and Ⅲ) ( n ＝ 100 each).Each group was further divided into 2 subgroups ( n ＝ 50 each):parecoxib group (groups P1.2.3 ) and control group (groups C1,2.3 ).In groups P1.2.3 psrecoxib 40 mg was administered iv at the end of operation while in groups C1.2.3 normal saline (NS) was administered instead of parecoxib.Groups Ⅰ,Ⅱ and Ⅱ received a loading dose of morphine 2.0/1.5/1.0 mg+ 0.15％ ropivacaine 8 ml respectively.The PCEA solution contained morphine 3.0/2.0/1.5mg+ ropivacaine 150 mg + granisetron 3 mg+ dexamethasone 5 mg in 100 ml of NS in groups Ⅰ,Ⅱ,and Ⅲ respectively.PCEA pump was set up with a background infusion of 2 ml/h,and a bolus dose of 0.5 ml with a lockout-interval of 15 min.VAS was used to assess intensity of pain (0 ＝ no pain,10 ＝ worst pain).VAS score ≤4 was considered as effective analgesia.Adverse effects including nausea and vomiting and pruritus were recorded.ResultsThere was no significant difference in the rate of effective analgesia between groups P1,P2 and C1,C2 The rate of effective analgesia during movement was significant higher in group P3 than in group C3.The incidence of nausea and vomiting and pruritis were significantly lower in group P3 than in groups P1 and P2.Conclusion Parecoxib can enhance the efficacy of PCEA with small dose of morphine.