Sun Pharma informed the 126 staff of the decision at a meeting today.
In a statement to Tipp FM the company put the decision is down to efforts to keep in line with customer demand and avoid over-capacity.
Many locals describe the closure as the end of an era having grown up with Ranbaxy on their doorstep for around 30 years.
Unions and management at Sun Pharma are to meet next week to discuss redundancy packages.
Production is set to cease on April 28th with full closure by the end of the year.
Sun Pharma completed a merger with Ranbaxy in March of last year – within months they were seeking to sell the site as a going concern.
Unite Trade Union rep Tony Kelly says it's not unreasonable for workers to be suspicious that Sun Pharma always intended to close the facility.
