GlaxoSmithKline, one of the world's largest pharmaceutical makers, has agreed to pay $750 million to resolve Justice Department allegations that the company sold adulterated and improperly made drugs.

The actions are the result of a long-running federal investigation of the company's former drug manufacturing plant in Cidra, Puerto Rico. A company subsidiary agreed Tuesday to plead guilty to allegations that the plant churned out medications that were mislabeled, mixed up in the wrong packaging, and even defective -- made either too weak or too strong. The defects affected such popular prescription drugs as the antidepressant Paxil and the ointment Bactroban, used to treat skin infections.

The government claimed that the plant mixed different strengths of some pills together, such as both 30 mg and 10 mg tablets in the same bottle, and that Bactroban and Kytril, an anti-nausea medication, were contaminated with microorganisms.

The plant's manufacturing process caused Paxil CR tablets, made in two layers, to split apart, the Justice Department said. As a result, a patient could take a dose with no therapeutic effect or one that contained no controlled release mechanism.

The company closed the plant in Cidra in 2009 and no longer owns it.

A big factor in the lawsuit was the role of a former manager of quality assurance for GSK, Cheryl Eckard, who became a whistleblower after she was fired. She will receive roughly $96 million from the federal share of the settlement.

"We regret that we operated the Cidra facility in a manner that was inconsistent with current good manufacturing practice requirements and with GSK's commitment to manufacturing quality," said PD Villarreal, senior vice president and head of global litigation.

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Deficiencies at a separate drug plant in Puerto Rico led the Food and Drug Administration Tuesday to withhold approval of a new drug for another pharmaceutical company, Bristol-Myers Squibb. The FDA said an inspection found possible contamination and detected glass particles in drug vials at the plant in Manati. Those problems must be resolved, the FDA said, before approval is granted for sales of belatacept, intended to prevent rejection of transplanted organs.