KV Pharmaceutical sued the maker of generic drugs Perrigo Co., alleging patent infringement with its plans to make low-cost copies of the drug Gynazole used to treat female yeast infections.

KV, based in Bridgeton, is asking a federal judge in Delaware to rule that Perrigo's sale of its version of the medicinal cream would violate U.S. patent laws and to stop Perrigo from marketing the drug until the patent expires in 2017.

"Plaintiffs will be irreparably harmed" without court intervention, KV contends in court papers filed Thursday, which also seek attorneys fees.

Perrigo, based in Allegan, Mich., makes store-brand drugs. It reported $2 billion in sales for the fiscal year that ended in June 2009. Its shares have risen about 40 percent this year.

For the past 18 months, KV has languished because its production plants have been closed, in part, for failing to meet federal standards. The company reported a $313.6 million net loss on $312.3 million in sales for the fiscal year that ended in March 2009. Its stock has fallen about 70 percent this year. As a result, the company has been forced to shed payroll to compensate for declining revenue. KV employed 1,700 workers as recently as 2008; now that total is fewer than 400.

Earlier this year, a KV subsidiary — Ethex Corp. — pleaded guilty to federal charges of failing to inform the FDA that it was manufacturing oversized tablets that could be harmful to patients.

In June, KV announced that it had sold its Particle Dynamics subsidiary to an Ohio investment fund to help raise enough cash to stay afloat until production resumes. As part of the sale, the company received $24.6 million, company officials said.

The Post-Dispatch contributed to this report.