Objective      To observe the dynamic changes of the expression of P-glycoprotein（P-gp）in peripheral blood in children with epilepsy

and to explore the relationship between P-gp and epileptic resistance and its value of predicting efficacy of antiepileptic drugs (AEDs).       Methods      A total of 70 inpatients and outpatients in our department from January 2011 to July 2012 were subjected in this study. These children were divided into refractory epilepsy (group A

n=30

age ranging from 13 months to 15 years)

and newly diagnosed epilepsy（group B

n=40

age ranging from 2 months to 14 years). Another 30 sex and age matched healthy children (group C) served as normal control. The expression of P-gp in peripheral blood was detected by flow cytometry before treatment

and in 6

12 and 18 months after treatment

respectively. The expression of P-gp and its relationship with epileptic frequency and therapeutic effect of AEDs were analyzed.       Results      The expression of P-gp in group A and group B at every time point were all significantly higher than that in group C（P0.01)

and that in group A were all significantly higher than that in group B（P0.01). Significant difference was also found in the expression of the P-gp in group A at difference time points（P0.01，P0.05)

but was not found in group B. Among the 19 cases with positive P-gp before treatment in group A

16 out of them (84.2%)were invalid after changing or adding AEDs

but only 3 out of 11 cases (27.3%)with no P-gp expression became invalid

and there was a significant difference between them （P0.01). In group B

9 out of 13 cases (69.2%)with P-gp expression before treatment became intractable

but only 2 out of 27 (7.4%) with no P-gp expression became intractable

there was a significant difference between them （P0.01). P-gp expression was stronger in the patients with high frequent epilepsy than those with low frequency（P0.01). P-gp expression was also stronger in patients administered with 4 kinds of AEDs than those with 2 or 3 kinds of AEDs（P0.01).       Conclusion      The high level of P-gp increase in peripheral blood of children with epilepsy predicts refractory epilepsy. The increased expression of P-gp may play an important role in clinical drug resistance. It also can be used as a predictable marker of evaluating efficacy of AEDs.