Tenofovir for Hepatitis B Suppression
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Viread®, also known as tenofovir disoproxil fumarate, is a medicine used to treat chronic Hepatitis B. Since there are so many variables involved in treating the Hepatitis B virus, navigating through the medications can be confusing. If you are considering taking tenofovir, make sure you understand this powerful drug’s strengths and weaknesses.
One of the newest antiviral drugs approved by the U.S. Food and Drug Administration (FDA) to treat Hepatitis B, tenofovir is a nucleotide analogue reverse transcriptase and Hepatitis B polymerase inhibitor. This type of drug interrupts important steps in the virus’s reproductive cycle by stopping or interfering with DNA formation or replication. Although considered to be one of the most potent Hepatitis B medications, a 300-mg daily tablet of Viread® does not cure Hepatitis B. However, it is gaining a great deal of support because tenofovir:
- can significantly reduce Hepatitis B viral load.
- helps a small percentage of infected people clear the Hepatitis B virus.
- has a low potential for drug resistance.
- may improve the liver’s condition.
The Hepatitis B virus’s reproductive cycle is complex, and each type of antiviral medication disrupts a different step in that cycle. Over time, the Hepatitis B virus can develop drug resistance by mutating to avoid harm from a specific drug. Because antiviral drugs are typically taken for a long stretch of time, choosing a medication with a low incidence of drug resistance is highly desirable.
Although there are many factors that contribute to a decision on how to treat chronic Hepatitis B, therapy is usually advised when:
- Those who are Hepatitis B e antigen (HBeAg)-positive have a DNA level of greater than 20,000 IU/mL and when serum alanine aminotransferase (ALT) is elevated for 3-6 months.
- Those who are Hepatitis B e antigen (HBeAg)-negative have a DNA level of greater than 2,000 IU/mL and when serum ALT is elevated (ALT levels >20 U/L for females; 30 U/L for males) for 3-6 months.
Currently, tenofovir is one of four primary drugs used to help treatment-naïve Hepatitis B patients – although ongoing trials are investigating many new substances and drug combinations. The four drugs used as a first-line treatment for Hepatitis B include:
- interferon alfa (IFN-a)
- adefovir
- entecavir
- tenofovir
While a knowledgeable physician’s expertise is needed to ascertain the right treatment for any person, several studies involving tenofovir give us encouraging information about this drug.
- Being a relative newcomer to the Hepatitis B arsenal, there is limited safety information for this drug. However, a study published August 2011 online in Hepato-Gastroenterology found that tenofovir was safe and effective in the long-term management (three years) of HBeAg-positive and HBeAg-negative patients with chronic Hepatitis B.
- Since spontaneous reactivation of chronic Hepatitis B virus can cause a sudden, severe worsening of liver disease, Indian researchers sought alternatives to a liver transplant for those with acute-on-chronic liver failure. As published in the March 2011 edition of the journal Hepatology, they found tenofovir to significantly reduce Hepatitis B viral load and improve the liver’s condition in those with severe spontaneous reactivation of chronic Hepatitis B presenting as acute-on-chronic liver failure. The outcome with tenofovir greatly reduced the mortality rate in this group of high-risk individuals.
No potent drug is without its caveats, Viread® included. According to the manufacturer, Viread® can cause serious side effects, including:
- Lactic acidosis – A buildup of acid in the blood is a serious medical emergency that can be fatal. Signs that require immediate medical attention include feeling very weak or tired, unusual muscle pain, breathing difficulty, stomach pain with nausea/vomiting, feeling cold (especially in the arms and legs) feeling dizzy or lightheaded, or having a fast or irregular heartbeat.
- Severe liver problems – Be aware that the liver can become enlarged or fatty with this medication. Signs of a severe liver problem that require immediate medical attention include jaundice (yellow skin or whites of the eyes), dark-colored urine, light-colored stool, loss of appetite for several days, nausea or stomach pain.
- Exacerbating factors – Lactic acidosis or severe liver problems are more likely to occur in females, those who are obese or those who have been taking Viread® or similar medicine for a long time.
- Flare-up – Hepatitis B infection may worsen if Viread® is stopped. Therefore, stopping this medication must be done under the advice and guidance of a knowledgeable physician.
So far, the data that has surfaced demonstrates tenofovir to be a key player in managing the chronic Hepatitis B virus. Although this medication can suppress viral load and improve liver health, it is not a cure for Hepatitis B. In addition, only time will tell if drug resistance remains low with Viread® and if long-term use of tenofovir is safe.
References:
http://emedicine.medscape.com/article/177632-treatment, Hepatitis B Treatment and Management, Nikolaos T Pyrsopoulus, MD, PhD, MBA, FACP, Retrieved December 25, 2011, WebMD, LLC, 2011.
http://onlinelibrary.wiley.com/doi/10.1002/hep.24109/abstract, Tenofovir improves the outcome in patients with spontaneous reactivation of hepatitis B presenting as acute-on-chronic liver failure, Hitendra Garg, et al, Retrieved December 25, 2011, Hepatology, March 2011.
http://www.gastrojournal.org/article/S0016-5085(10)01499-X/abstract, Three-Year Efficacy and Safety of Tenofovir Disoproxil Fumarate Treatment for Chronic Hepatitis B, E. Jenny Heathcoate, et al, Retrieved December 21, 2011, Gastroenterology, January 2011.
http://www.hbvadvocate.org/hepatitis/factsheets_pdf/Treatment-first.pdf , Which Hepatitis B Drug Treatment to Use First, Christine M. Kukka, Retrieved December 25, 2011, Hepatitis C Support Project, 2011.
https://www.hepato-gastroenterology.org/?p=1897, Comparison of the Efficacy of Entecavir and Tenofovir in Chronic Hepatitis B, Fatih Guzelbulut, et al, Retrieved December 21, 2011, Hepato-Gastroenterology, online August 2011.
http://www.hivandhepatitis.com/hep_b/news/2011/0510_2011_a.html, Tenofovir Improves Outcomes of HBV Acute-on-Chronic Liver Failure, Liz Highleyman, Retrieved December 24, 2011, hivandhepatitis.com, 2011.
http://www.viread.com/en/, VIREAD®, Retrieved December 21, 2011, Gilead Sciences, Inc, 2011.
