Workers at Teva, one of the biggest pharmaceutical factories in Waterford, have been told that 315 jobs are to go at the plant.
The plant manufactures inhalers and tablets.
The tablet production will cease at the factory within 12 months with the loss of the jobs.
The redundancies will be a mixture of voluntary and compulsory but details of packages have not yet been released.
A part of the manufacturing of tablets will be transferred to a factory in Hungary.
There are around 730 people employed at the Waterford facility, which is on the IDA Industrial Estate.
Teva is owned by an Israeli consortium and was formally known as IVAX.
Similar jobs vulnerable
Speaking about the job losses, Matt Moran of PharmaChemical Ireland, an umbrella body for the pharmaceutical industry, said between 500 and 1,000 similar jobs could be vulnerable.
He said the cost base for manufacturers in Ireland has risen and that producing generic pharmaceuticals which are off patent is very susceptible to competitive pressure.
Mr Moran said manufacturing generic pharmaceuticals represents between 5% and 10 % of the sector in Ireland.
Elsewhere, the multinational eyecare company Bausch and Lomb has announced that 500 jobs are to go at its facility in Scotland, a move which may help safeguard jobs in Waterford.
The company said that as part of a restructuring process, approximately 30 new positions will be created in Rochester in the US during 2010 but there will be no employment increase in Waterford.
The company proposal will affect approximately 500 employees in Livingston, Scotland on a staggered basis through the next 14 to 18 months.
General manager of Bausch & Lomb Ireland Colum Honan said the proposal to move highly-automated production lines to manufacture daily disposable lenses in Waterford and Rochester was a positive development in the short to medium term.
The company currently employs 1,100 in Waterford.