Entecavir for Treatment of Lamivudine-refractory Patients Chronic Hepatitis B H.T. DAT 1 , P.T.T. THUY 1 1 MEDIC Medical Centre, Ho Chi Minh, Vietnam Lamivudine treatment is associated with frequent development of resistant hepatitis B virus. This incidence especially is higher in longer time of treatment and loss of treatment benefit. Entercavir is a new antiviral agent shown its high efficacy even in cases of mutations with Lamivudine resistance. In this study, we evaluate the efficacy, the safety of Entercavir in treatment of Lamivudine-refractory patients chronic hepatitis B. Sixty chronic hepatitis B patients with evidence of Lamivudine resistance were randomly divided into two groups in proportion of 3:1. Group I (n=45) used Entecavir 1mg/day, group II (n=15) used Lamivudine 100mg/day. Treatment time was 48 weeks. Histology, ALT, HBVDNA were evaluated in the end of the treatment. Age, sex, ALT, HBVDNA, genotype, HBeAg were analyzed to evaluate their influences to the treatment. The results have showed HBVDNA<2000 copies/mL in Entecavir group 37.78% vs. 0% Lamivudine group (p<0.01). HBVDNA negative in Entecavir group was 17.77% and incidence of seroconversion of HBeAg was 8.82%. ALT was normal in Entecavir group 77.77% vs. 26.66% in Lamivudine group (p<0.001).Histologic improvement in Entecavir group was 37.77% vs.6.66% in Lamivudine group (p<0.05). Patients with HBeAg negative, genotype B, low viral load were shown better results. Entecavir was shown to be efficacious in treatment for chronic hepatitis B patients experienced with Lamivudine resistance. Entercavir is safe, with almost no side effects. Factors such as HBeAg negative, genotype B, low viral load seems to be better in response to treatment. Recurrence or mutation of Entecavir resistance should be studied further in future.