Pfizer (NYSE:PFE) has begun to layoff its primary-care sales representatives in order to cut costs. This year, the drug manufacturer’s revenue contracted significantly because of patent expirations of several key drugs, and therefore the company has been forced to offset losses by employing a smaller sales force.

“As part of our strategy to allocate our resources, investments and people to the areas that best serve our patients and customers, we continually evaluate how we can be more efficient and effective,” Pfizer spokesman MacKay said in a statement seen by MarketWatch.

Previously, Pfizer’s primary care division was the company’s largest by sales. However, sales shrank in 2012 as its blockbuster cholesterol-lowering medication Lipitor lost patent protection last year. In 2011, the drug generated $9.6 billion in sales, or 14 percent of the company’s total revenue. However, partly due to diminished Lipitor sales, the pharmaceutical manufacturer’s revenue fell by 18 percent to $5.63 billion in the third quarter of this year.

Following these results, the company’s Chairman and Chief Executive Officer Ian Read said, “Overall, our results this quarter reflect continued product losses of exclusivity, most notably Lipitor in all major markets.”

But the company is not alone; AstraZeneca (NYSE:AZN), Abbott Laboratories (NYSE:ABT), and Bristol-Myers Squibb (NYSE:BMY) announced layoffs earlier in the year.

The pharmaceutical company gave no details as to how many salespersons would lose their jobs.