A federal judge on Monday ordered an Irish drug manufacturer to halt its plans to discontinue its widely used Alzheimer's medication, allegedly in an effort to drive patients to a newer patented drug.

U.S. District Judge Robert Sweet told Dublin-based Actavis PLC to continue making the drug Namenda available for 30 days after generic alternatives become available on July 11 "in order to allow for an orderly transition."

His injunction orders the company to inform doctors and pharmacists of the decision and tells Actavis not to impose any hurdles for filling prescriptions of the drug.

Actavis said it will appeal Monday's ruling. The company said its new drug Namenda XR - taken once daily instead of twice - is better and demand is growing.

The ruling will have "no impact on its ability to continue focusing its resources on transitioning patients" to the new drug, Actavis said. It is "prepared to manage its business in a way that provides the least disruption in its ability to support the marketplace and minimize any financial impact."

New York Attorney General Eric Schneiderman sought the court order. He alleged that Actavis and New York subsidiary Forest Laboratories violated anti-trust and state laws in an effort to avoid losses from cheaper generic alternatives coming out next year.

"Unfortunately, schemes to block competition, without considering the consequences to patients, are a growing trend in the health care industry," Schneiderman said when he filed the lawsuit in September. His office is looking at other drugs and companies.