Vintage Pharmaceuticals, a generic drug manufacturer, has pleaded guilty to felony charges of distributing adulterated drugs through interstate commerce.

According to the U.S. Attorney's Office in the Western District of North Carolina, Vintage admitted that from January to October 2000 it introduced roughly 50 million tablets of Levothyroxine Sodium, USP -- a drug aimed at controlling hypothyroidism -- into commerce, knowing that its methods to assign expiration dates on the drugs did not conform with good manufacturing practices set by the FDA.

Since the tablets did not meet purported quality and purity characteristics, the U.S. Attorney's Office said, they risked falling below the FDA-required potency limits before the expiration date placed on the label, and consumers who relied on the drug could not be sure it was safe and effective.

William Propst Sr., president and CEO of Vintage, pleaded guilty to 19 misdemeanor counts of distributing adulterated drugs. His son, William Propst Jr., assistant to the president during this time period, pleaded guilty to one misdemeanor count of the same nature.

In a separate pleading, Frances Hutchins, ex-manager of Vintage's Charlotte operations, pleaded guilty to one misdemeanor count of distributing adulterated drugs into interstate commerce, adding that she failed in her duty to refuse an order from Vintage's president to release the adulterated lots of Levothyroxine Sodium, USP.

Vintage will pay $4.8 million in fines and forfeit $1.2 million in proceeds from criminal activity.