GlaxoSmithKline (NYSE: GSK) slashed 10 percent of the work force at its pharmaceutical manufacturing plant in Zebulon on Friday morning.

Some 90 production workers lost their jobs, according to Gigi Nelson, who is the human resources director at the facility.

“They were told today that their positions are being eliminated,” Nelson said.

Between 850 and 900 remain employed at the plant, down from 1,350 in June 2007.

The layoffs are part of a continuing review within the ranks of the pharmaceutical giant, which employs some 5,000 people across the Triangle.

The Zebulon GSK plant manufactures the asthma drug Advair, metered dose inhalers and other tablets.

No production lines or departments are being closed, Nelson said.

In February, GSK laid off some 70 workers. At that time the plant’s work force was approximately 1,050, according to the company.

Last October, GSK announced plans to pare its international work force as part of cost-cutting measures. GSK has already shuttered production plants in Puerto Rico and the United Kingdom and recently laid off some 150 research and development personnel.

Nelson said the Zebulon plant remains a “critical” part of GSK, but added that there are “no guarantees” there won’t be further layoffs in the future.

Earlier this week, GSK reported a 3 percent drop in second-quarter profits to $2.6 billion from the same time period in 2007. Revenues did increase 3.5 percent to $11.8 billion.

However, GSK forecast a continuing decline in earnings over the next year, citing increased competition from generic drugs. GSK also has suffered from plunging sales of its diabetes drug Avandia, which has been linked to an increased risk of harmful side effects.