[Entecavir].

Chronic hepatitis B continues to be a serious problem worldwide. Because a high viral load is associated with greater progression to cirrhosis and hepatocarcinoma in these patients, new drugs that achieve rapid, potent and lasting suppression of viral replication must be sought. Entecavir is a new, highly potent antiviral agent; phase II and III studies have demonstrated this drug to be superior to placebo and lamivudine in patients with chronic hepatitis B virus in terms of histological improvement, efficacy in achieving suppression of viral replication and normalizing transaminase counts. The drug is well tolerated, since its adverse effects are usually mild or moderate and their incidence is similar to that found with placebo or lamivudine. Moreover, in treatment-naïve patients, no resistance has been observed after 3 years of therapy. However, in patients with prior resistance to lamivudine, the incidence of resistance is approximately 15% at 3 years. Further studies are required that compare this drug with other currently available therapeutic options, as well as longer term trials to evaluate its safety. It seems that entecavir will occupy a major place in the treatment of patients with chronic hepatitis B virus infection.