The Irish Examiner understands that between 120 and 130 jobs will go at the Ringaskiddy plant and the remainder at Little Island, where the cholesterol reduction drug Lipitor is produced.
Lipitor came off patent in America in Nov 2011 and in Europe last month, resulting in fears among the Little Island workforce that the plant would be closed and production transferred to the Ringaskiddy facility.
Lipitor is the biggest selling medicine in the world, earning Pfizer $14bn (€11.2bn) a year.
The fallout from expiration of patent, and other medicines due to come off patent, is that the company is seeking to cut €80m from its Irish operations.
Job losses will be across the board. The pharmaceutical company currently employs more than 700 workers at both Cork plants, 500 in Ringaskiddy and 220 in Little Island.
News of the job losses comes following months of speculation about a major costs reduction programme by the pharmaceutical giant.
One staff member, who asked to remain anonymous, told the Irish Examiner: “We have chased the company for an age for an earlier response, but have been unable to get one.
“People here are anxious about the future and need to know if they are going so that they can prepare for a new career.”
There had been speculation among the staff that production of Lipitor would be moved to Ringaskiddy and the Little Island site either closed or sold.
Asked about the job cuts, a Pfizer spokeswoman would not comment.
“Pfizer does not comment on speculation — if and when there is any information on company activities, that information will be shared first with colleagues,” she said.
The job losses come just over two years after the company announced that it was letting almost 800 of its 5,000 Irish employees go as part of a global purge of 6,000 positions.
At that point Pfizer said it was closing two plants in Cork — Loughbeg and Shanbally — and its plant in Dún Laoghaire, Dublin, as well as downsizing its operation in Newbridge, Co Kildare.
At the time Dr Paul Duffy, the man leading its operations in Ireland, said the cost of operating in Ireland had got “out of whack” and “out of hand”.
“We are still one of the more costly environments that Pfizer would have around the world,” he said at the time.
Ultimately, there was to be good news for the Shanbally plant as last June it emerged that another company, BioMarin Pharmaceutical, was to take over the facility with the creation of 100 jobs over five years.
Pfizer has been operating in Ireland since 1969 when it built its first plant in Ringaskiddy.
By 1994, it had invested more than €1bn here and two years later began developing Lipitor.