Federal regulators approved a new drug from Johnson & Johnson for use in treating chronic hepatitis C infections. The Food and Drug Administration said it had approved the drug, a protease inhibitor that blocks a protein needed by the virus to replicate. The drug, named Olysio, is designed to eliminate hepatitis C, the most common form of the liver-destroying virus. It is a daily pill taken in combination with the long-established drug cocktail used to treat the most common form of the virus. The decision comes less than a month after an advisory panel voted unanimously in favor of approving the treatment. Olysio is the third approved protease inhibitor for treatment of hepatitis C, the agency said.