Medical Health Encyclopedia

Lamivudine and Entecavir. These two drugs are classified as nucleoside analogs. Lamivudine (Epivir or 3TC) is an antiretroviral drug that is used to treat human immunodeficiency virus (HIV) as well as hepatitis B. Lamivudine has reduced viral count in over half of hepatitis B patients who have taken it as sole therapy for about a year. It is less expensive than interferon-alfa and has fewer side effects, but may not be as effective as interferon-alfa for long-term therapy. A major problem with lamivudine is the development of mutated viral strains that become resistant to the drug, particularly in areas where the virus is common. In 2005, the FDA approved entecavir (Baraclude) for treatment of adults with chronic hepatitis B. In clinical trials, entecavir was more effective than lamivudine for treating HBV. However, questions have been raised about the drug’s possible cancer risks. Ongoing studies are assessing this risk.

Adefovir. Adefovir (Hepsera) belongs to a class of antiviral agents called nucleotide analogs. (Nucleotides are related to nucleosides but have a slightly different chemical structure.) Nucleotide analogs block an enzyme involved in the replication of viruses. Adefovir costs more than lamivudine, but may be effective against lamivudine-resistant strains of HBV.

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Drug Warnings. In 2004, the FDA issued two drug warnings for patients with HBV. The HIV drug tenofovir (Viread) should not be used to treat patients who are co-infected with HBV as the drug may increase hepatitis severity. The lymphoma drug rituximab (Rituxan) may reactivate HBV. Patients with lymphoma should be screened for HBV.

Investigative Drugs for Hepatitis B

• Telbivudine is a nucleoside analog drug in Phase III trials for treatment of chronic hepatitis B. A 2003 study, presented at a meeting of the American Association for the Study of Liver Diseases, found that telbivudine resulted in significantly better suppression of HBV and normalization of certain liver enzymes compared to lamivudine monotherapy.
• Pegylated interferon alfa-2b (Peg-Intron) is currently approved for treatment of chronic hepatitis C. It is being investigated alone and in combination with lamivudine for treatment of HBV. One 2005 study found that a third of patients treated solely with pegylated interferon-alfa-2b became negative for the hepatitis B antigen (HBeAg). Combining the drug with lamivudine did not improve effectiveness. Another 2005 trial tested a staggered drug regimen where pegylated interferon alfa-2b was administered alone and then later combined with lamivudine. Researchers compared the results with lamivudine single therapy and found that the combination group had better virologic response and less drug-resistance. However, there were more side effects in the combination drug group and the duration of the treatment regimen was longer.
• Thymosin Alpha 1 (Zadaxin), also called thymalfasin, is a synthetic version of a peptide derived from the thymus gland (which is responsible for maturation of immune factors call T-cells). It appears to be safe for hepatitis B patients when used alone or in combination. It is approved in many countries, but not the United States.
• Vaccines as Treatments. Hepatitis B vaccines are being investigated in combination with drugs, such as lamivudine, for treatment of HBV.

Treatments for Primary Biliary Cirrhosis