Under a ruling by a US court of appeals upholding a preliminary injunction dating from December 2014, Ireland-headquartered former US drugmaker Actavis will have to continue selling its Namenda IR tablets for treatment of moderate to severe Alzheimer's type dementia.

The ruling puts paid to a plan by the company to pull the drug, which will face generics competition from mid-July, from the market and switch patients to Namenda XR, a higher dose, once-daily formulation.

Actavis has appealed the decision to the next instance, but analysts said a "second opinion" could come too late to stop the generics competition in its tracks.

The drugmaker has launched another new product, Namzaric, a fixed dose, once-a-day combination of Namenda XR and Aricept (donepezil), which it plans to market directly. The two drugs are said to be often prescribed together to treat the symptoms of moderate to severe Alzheimer's disease.

Actavis has said it will work to ensure that the court's decision has little to no impact on its 2015 Namenda franchise contribution to earnings as well as its longer-term earnings targets.