HAYWARD, Calif. (AP) — Impax Laboratories Inc. said Wednesday it is challenging the patents on Avanir Pharmaceuticals Inc.’s drug Nuedexta, and it said Avanir has filed a patent infringement lawsuit.

Avanir began selling Nuedexta in February. The drug is approved as a treatment for pseudobulbar affect, a condition that involves involuntary emotional outbursts like laughing or crying. It is associated with brain disease or injury. Impax said U.S. sales of Nuedexta since its launch totaled $3.6 million.

Impax said Avanir, of Aliso Viejo, Calif., filed a patent infringement lawsuit in Monday in the District of Delaware. As a result of the lawsuit, the Food and Drug Administration will not approve Impax’s application for 30 months or until the court makes a ruling on the patents, whichever comes first.

Avanir said on Aug. 11 that it is suing two other companies that want to market generic versions of Nuedexta. Par Pharmaceutical Cos. and Actavis Inc. had also asked the FDA to approve their generics.

Shares of Impax rose 35 cents to $19.75 in afternoon trading. Avanir shares fell 14 cents, or 4.7 percent, to $2.82.