The Food and Drug Administration approved the first oral therapy for liver-destroying hepatitis B on Wednesday.
Glaxo Wellcome Inc.'s drug 3TC, or lamivudine, helps protect against liver damage caused by chronic hepatitis B. It is already used to fight the virus that causes AIDS.
The FDA approved use of a lower 3TC dose for hepatitis patients than is taken by patients with the AIDS virus. Glaxo will sell the special hepatitis dose under the brand name Epivir HBV. The daily hepatitis dose will cost $3.41 wholesale, half the price of the higher AIDS dose.
3TC cannot cure hepatitis B, which infects an estimated 1 million Americans and can cause cirrhosis or liver cancer.
But 3TC is one of several drugs that block production of reverse transciptase, an enzyme used by both HIV, the AIDS virus, and the hepatitis B virus to reproduce. Using it thus lowers the hepatitis in patients' blood and improves the liver's health, studies show.
In one study of Americans with mild to moderate infection, 55 percent who took 3TC pills showed improvement when doctors took liver biopsies, versus 25 percent of patients who took a dummy pill.
Until now, the only FDA-approved treatment for hepatitis B was injections of a drug called interferon-alpha.
No one yet knows how long hepatitis patients should take 3TC, which was studied for just a year, the FDA said.
The biggest warning: hepatitis patients need an HIV test before trying the new hepatitis drug, and repeated testing during therapy. That's because if they have undiagnosed HIV, taking too low a 3TC dose could cause the HIV to develop dangerous drug resistance.
The drug's side effects include nausea, diarrhea, and occasionally more serious effects like liver enlargement, although more problems are reported at the higher HIV dose, the FDA said.