Some 133 workers are facing redundancy after healthcare giant Johnson & Johnson announced plans to shut its factory in Cashel.
The US multinational is closing the Tipperary facility after it decided to end manufacturing of two special coronary stents.
David Kinahan, general manager at the plant, said the closure was not a reflection on the staff. "Today is a very difficult day for all of us," he said.
"There are strategic business reasons behind the cessation of the NEVO coronary stent programme, and the intended closure of the Cashel operations where the Nevo stent is manufactured, is a direct result of that decision."
The Cashel plant was run by the Cordis Corporation, a Johnson & Johnson company, and made special medical devices, the Nevo Sirolimus-Eluting Coronary Stent and the Cypher stent.
In a statement the company said it was no longer pursuing the development of the stents as a result of evolving market dynamics and product portfolio decisions.
Bryan Mohally, vice-president of Johnson & Johnson supply chain operations, said: "Johnson & Johnson is committed to Ireland, and has a very large presence here stretching back to the 1930s with some 10 business units, including four large manufacturing sites."
He suggested Johnson & Johnson may examine new options for the factory.
Tom Hayes, Fine Gael TD for South Tipperary, said: "I feel enormous sympathy for the affected workers who will be left devastated. To lose your job is a terrible blow and the resulting uncertainty and financial pressure is very difficult for families to deal with.
"The company had invested hugely in the plant in Cashel and it is very disappointing to see this development."