Hep B Blog

Taking Antivirals Long-Term for Hepatitis B? Should You Worry About Bone Loss?

Image courtesy of Sira Anamwong at FreeDigitalPhotos.net.
Image courtesy of Sira Anamwong at FreeDigitalPhotos.net.

By Christine Kukka

To prevent liver damage and cirrhosis and reduce the risk of liver cancer–especially in older patients who’ve had hepatitis B for decades–doctors often prescribe long-term antiviral treatment. But some antivirals cause minor bone loss, which poses a problem for older patients with osteoporosis.

According to experts, the risk of bone loss from long-term antiviral treatment is low, and in fact some antivirals do not cause any bone loss at all. But if you are starting antivirals at an older age, or if you have been on antivirals long-term, experts recommend you monitor your potassium and vitamin D levels and regularly test for bone loss in the hip area so you know if you are experiencing bone loss and need a calcium or vitamin D supplement.

Antivirals affect bone health by causing a reduction in the amount of phosphorus in your body; a mineral that is essential to bone health. Historically, the antivirals lamivudine (Epivir-HBV) and adefovir (Hepsera) were widely used and adefovir specifically was linked to bone loss. Neither of those antivirals are currently recommended for first-line treatment.

Today, the antivirals entecavir and tenofovir are recommended for most patients. Here is how these two antivirals affect bone health.

Entecavir (Baraclude) appears to cause no bone loss, according to hepatitis B expert Dr. Robert Gish, medical consultant to the Hepatitis B Foundation and professor consultant of gastroenterology and hepatology at Stanford University. This antiviral, which recently became available as a less-expensive generic, has proven highly effective in reducing viral load (HBV DNA) and reducing liver damage in patients who are taking an antiviral for the first time.

If you are an older patient, have signs of bone loss, and have never been treated with an antiviral before, your doctor may recommend this daily antiviral pill. However, entecavir is not an option if you’ve already been treated with an antiviral, such as lamivudine, and developed drug resistance.

Tenofovir (Viread) is a potent antiviral that is effective in all patients, including those with drug resistance. Researchers have detected no drug resistance even after seven years of tenofovir treatment.

However, tenofovir causes a slight increase in bone loss in the lower hip area, according to recent studies. Those most at risk of bone loss are older, smoke, and have low body mass or low levels of vitamin D.

“With tenofovir, there is a very low risk of bone loss, yet enough that education and monitoring are advised,” Dr. Gish explained. “To prevent bone loss when taking tenofovir, patients should take 1,200 mg of calcium per day and keep their vitamin D levels (identified by a blood test) in the 40-50 range.”

How to check for bone loss when taking antivirals. To find out if your antiviral treatment is causing bone loss, Dr. Gish and medical experts recommend a bone mineral density scan, called a dual-energy x-ray absorptiometry or DXA scan, to measure bone health. “Your primary care provider can order this and can be aware of any problems,” he said.

Another test for bone health is a blood test, called a PO4 test, for phosphorus, the mineral needed for healthy bones. According to Dr. Gish, fewer than 3 percent of hepatitis B patients who take tenofovir experience a decline in phosphorus levels. Normal phosphorus levels range from 2.4 to 4.1 milligrams per deciliter (mg/dL). Dr. Gish recommends PO4 tests every year to monitor bone health.

If you are just starting antivirals and face long-term treatment, talk to your doctor about a baseline DXA scan, which should be repeated every three years while you are on treatment, and get annual phosphorus and vitamin D tests.

Talk to your doctor about a supplement to strengthen your bone health if your calcium or phosphorus levels fall below normal, or if your DXA scan shows bone loss. And, don’t forget to get healthy amounts of sunlight to help bolster your vitamin D levels.

The Institute of Medicine of the National Academies recommends sunlight exposure and the following daily recommended dietary allowance of vitamin D:

  • 15 micrograms (μg) per day or 600 international units (IU) for children, teens and adults up to age 70, including women who are pregnant or lactating,
  • And 20 μg per day or 800 IU per day for seniors age 71 and older.

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