The 450 strong workforce attended a meeting at 2pm today called by management where the announcement was made.
The 90 jobs are to go during the next six months due to falling demand for some of the company’s products.
Commenting on the news, Bandon Sinn Féin councillor Rachel McCarthy said, “The loss of these jobs is a major blow to the area and the local TDs really need deliver now on their pre-election promises of jobs and job retention.
“The affect this announcement has on the lives of these families and on the wider community is devastating.
“We in rural Ireland are watching the daily exodus of our youth to foreign shores while those in power sit on their hands.”
She added, “The real shame is that because of the constant neglect of rural Ireland by consecutive governments the prospects of moving to alternative employment in the region is low.
“The government needs to use every arm available to it in an effort to increase job prospects for those people facing redundancy today and to invest in future jobs in the area and protect the jobs that are still in place.”
A spokesperson for MSD said it was hoped that as many as possible of the redundancies could be achieved on a voluntary basis.
MSD announced 70 new jobs at the plant in 2011 and has an ongoing development programme for drugs to treat of cancer, Rheumatoid Arthritis, Hepatitis C and Crohn’s disease.
The plant was formerly operated by Schering Plough who were bought by MSD in 2009.