Examples

How It Works

Nucleoside reverse transcriptase inhibitors (NRTIs) are medicines that slow the ability of the hepatitis B virus (HBV) to multiply in the body. They are taken as pills once a day for at least a year, and usually much longer. Entecavir is also available as a liquid that you swallow.

Adefovir, entecavir, telbivudine, and tenofovir are approved by the U.S. Food and Drug Administration (FDA) for use in adults. Lamivudine is approved for use by adults and by children ages 2 to 17.

Why It Is Used

NRTIs are used to treat long-term (chronic) HBV infection in adults and children who are at risk for liver disease. The American Association for the Study of Liver Disease has made recommendations on who should receive treatment for chronic hepatitis B based on the presence of hepatitis B antigens in your blood, the level of hepatitis B virus DNA (HBV DNA) in your blood, and the levels of your liver enzymes.¹

How Well It Works

Treatment for HBV infection is considered successful if blood tests show that the virus is no longer multiplying in the body, if liver enzyme levels return to normal, and if liver damage (such as inflammation and scarring) improves. NRTIs work in most of the people who take them, but relapse (the virus starts to multiply again) is common after a medicine is stopped, so you may have to take the medicine for a long time.^{1, 2}

Some studies of entecavir show that it works better than lamivudine or adefovir.^{3, 4, 5}

Adefovir is effective against HBV infections that have become resistant to lamivudine, but adefovir costs more than lamivudine.¹ A study showed that treatment with adefovir worked better for some people with chronic hepatitis B if the medicine was taken for 144 weeks than if it was taken for only 48 weeks.⁶

Tenofovir is effective at reducing the amount of hepatitis B virus in the body.⁷

The hepatitis B virus may develop resistance to some of the NRTIs:¹

• After 1 year of treatment with lamivudine, up to one-third of hepatitis B viruses may be resistant to the medicine. After 5 years of treatment, up to 70% of HBV may be resistant to lamivudine.
• Resistance is less of a problem with telbivudine than with lamivudine. But resistance to telbivudine goes up greatly after one year of treatment.
• Resistance is less of a problem with adefovir. After 5 years of adefovir treatment, less than one-third of HBV may be resistant to the medicine.
• Resistance is rare with entecavir, especially when it is used as the first medicine to treat hepatitis B. It is more common when entecavir is used after lamivudine treatment.
• Tenofovir works better than adefovir against hepatitis B virus that is resistant to lamivudine.⁸
• Resistance to tenofovir has not been reported. But tenofovir is the newest NRTI approved to treat hepatitis B.