Months ~ years or permanently. Entecavir (ETV) is an oral prescription antiviral medication used to treat liver infections caused by the hepatitis B virus. This medication will not cure the hepatitis B virus, but it will stop it from reproducing and causing more liver damage. Entecavir is sold as a tablet to be taken by mouth once a day. The length of ETV treatment varies from person to person and is usually several months to several years, and may be required for a lifetime in some patients.

Studies have shown that in the Entecavir (ETV)-022 Treatment of Hepatitis B e Antigen (HBeAg)-Positive Chronic Hepatitis B Patients Study, 48 weeks of treatment with Entecavir 0.5 mg resulted in better virological suppression than lamivudine. In addition, the combination of ETV and tenofovir disoproxil fumarate (TDF) was associated with high potency of viral suppression, a high genetic barrier to drug-resistant mutations, and a good safety profile for long-term use. Therefore, long-term use of ETV/TDF may maintain viral suppression, improve liver histology, and prevent progression of liver fibrosis, liver-related complications, and mortality in patients with CHB.

Despite its clinical efficacy, CHB patients on long-term treatment are at risk of developing hepatocellular carcinoma (HCC). In a multicentre prospective cohort study of 1951 Caucasian adult patients with chronic hepatitis B who had received at least one year of ETV and/or TDF. The results showed an annual incidence of HCC of 1.22% within the first 5 years of treatment and 0.73% after the first 5 years of treatment. This suggests that patients with chronic hepatitis B taking ETV/TDF for a long enough period of time may one day be able to eliminate HCC. However, long-term clinical proof is needed to support this result.

References:

[1] T. YIP  G. W. How long will it take to eliminate HCC risk in patients with chronic hepatitis B patients with potent antivirals[J]. AME medical journal, 2017. DOI:10.21037/AMJ.2017.08.28.