NEW YORK (CNNMoney.com) - Getting sued seems to be the price of doing business for Big Pharma, and Wyeth has once again joined the ranks of the defendants.

This summer, the New Jersey-based drugmaker Wyeth (up $0.60 to $47.72, Research) faces the first of at least 4,000 lawsuits from former patients who took its menopausal treatment Prempro, a hormone therapy that provides relief from hot flashes and night sweats and can also help prevent osteoporosis.

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"The overwhelming majority of women in these cases suffer from breast cancer as a result of their use of Prempro," said lawyer Tobias Millrood, whose firm Schiffrin & Barroway is representing plaintiffs in about 1,000 Prempro cases. "Wyeth aggressively over-promoted these drugs for conditions that [weren't approved by] the FDA. [Prempro] was truly a panacea. This drug was promoted as the fountain of youth."

The first case is set to start on July 31 in federal district court in Little Rock, Ark. Plaintiff Linda Reeves, 67, of Benton, Ark., was diagnosed with breast cancer after taking Prempro for eight years for the prevention of osteoporosis, according to her lawyer, Jim Morris of Provost & Umphrey. Reeves blames Prempro for the cancer that led to her mastectomy.

"For women like Linda Reeves, the duration she took the product presents a dramatic risk for breast cancer," said Morris, who won a $1.4 million lawsuit against Wyeth in the infamous fen-phen case. "I've got a long history of battles with Wyeth, and we look forward to once again exposing their conduct to a jury."

In 1997, when Wyeth was called American Home Products, the company pulled its diet drug cocktail known as fen-phen off the market after it was linked to heart valve disease. In 1999, the company agreed to pay a $3.75 billion settlement, which was divided among thousands of former fen-phen users.

Millrood is representing the plaintiff in the second Prempro case, scheduled to begin Sept. 11 in state court in Philadelphia. Millrood described his plaintiff is a 67-year-old woman from Dayton, Ohio, who blames her six years of Prempro use for causing the cancer that led to her double mastectomy in 2001.

Wyeth spokesman Doug Petkus said that Prempro, which was introduced in 1995 and had sales of $1 billion last year, hasn't caused anyone's breast cancer and, unlike Merck's Vioxx, hasn't been pulled from the market.

"[Prempro] is still on the market and is used by millions of women," said Petkus. "It's effective and safe, per its label indication," he added, noting the drug was approved by the Food and Drug Administration.

Merck, the second-biggest drugmaker in America, also faces thousands of lawsuits over one of its drugs, the arthritis painkiller Vioxx.

But Petkus, the Wyeth spokesman, said his company's cases shouldn't be compared to Merck's ongoing litigation over Vioxx because Prempro remains on the market, while Vioxx was pulled for health reasons.

Millrood, the plaintiff lawyer, said that Prempro remains on the market only because of corporate manipulation.

"We are not deterred whatsoever by the fact that it's on the market," said Millrood. "We think it's to our advantage because we can point out the hypocrisy of their promotion."

Just last week, Merck (up $0.08 to $34.32, Research) was held liable by a Texas state jury in the latest case involving its withdrawn arthritis painkiller Vioxx, giving the drugmaker a 50-50 track record so far, with two wins, two losses, and one split verdict.

Vioxx was one of Merck's biggest drugs, with $2.5 billion in sales in 2003, its last full year on the market. Merck pulled the drug on Sept. 30. 2004, after a study showed that taking Vioxx for at least 18 months increased the risk of heart attacks and strokes.

Since then, about 11,500 lawsuits have been filed against the company, alleging wrongful death and accusing Merck of withholding negative information about Vioxx.

Merck denies any wrongdoing and says its drug hasn't killed anyone. Nonetheless, a Texas state jury last August held Merck liable for $253 million in damages, which will be capped to about one-tenth of that by state law. And on April 21, Merck was held liable by another Texas state jury for $32 million in damages, but that tally will also be capped to $750,000.

Part of the basis for the Prempro lawsuits against Wyeth are the results of a Prempro study conducted by the Women's Health Initiative that showed an increase in the risk of invasive breast cancer, according to the FDA.

But Barbara Ryan, analyst for Deutsche Bank North America, said she "didn't take [the data] very seriously," adding it wasn't strong enough to prove that Prempro causes breast cancer.

"People in the U.S. can sue for anything," said Ryan. "Four thousand people could sue me tomorrow. Whether they have grounds for it is another matter."

The analyst interviewed for this story does not own Wyeth stock but Deutsche Bank North America does.

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