A New Jersey-based generic drugmaker has agreed to pay $45 million to resolve criminal and civil liability charges for improperly marketing its weight-gain drug to frail seniors.

Officials from Woodcliff Lake-based Par Pharmaceutical Cos. pleaded guilty to a charge of criminal misbranding Tuesday in federal court in Newark.

Par officials admitted they improperly marketed their Megace ES drug for treating anorexia and malnutrition in geriatric patients who did not have AIDS. It's approved for helping AIDS patients gain weight.

The company has also agreed to enter into a five-year corporate integrity agreement with federal health officials and to drop a lawsuit it filed against the U.S. government.

Par agreed in July to be acquired by an affiliate of the private investment firm TPG for $1.84 billion.