Lois Takamori, a 62-year-old retired Kailua school teacher, was talking with friends at a gym in 2009 when a slight step backward broke her thigh bone.

Takamori filed a federal lawsuit Wednesday against drugmaker Merck & Co., claiming the thigh bone fracture was a result of taking the prescription drug Fosa­max for eight years.

Fosamax is commonly prescribed to postmenopausal women to prevent bone loss from osteoporosis, a condition prevalent among Asian and Caucasian women.

"I took onestep backward and felt excruciating pain," she said of the fracture. "It’sa devastating breakage because it doesn’t heal. I have discomfort, can’t walk without a cane, so it’s very limiting."

Takamori, who began taking Fosamax in 2001 when she was diagnosed with osteoporosis, had multiple surgeries to try to fix the fracture.

As of March 31, about 1,450 Fosamax cases had been filed in the U.S. against the pharmaceutical giant for osteonecrosis — a severe bone disease of the jaw — femur fractures and other bone injuries associated with long-term use of the drug, according to company filings with the U.S. Securities and Exchange Commission. Worldwide sales of Fosamax, a top-selling drug for Merck, were $208 million in the first quarter, a 10 percent decline from a year earlier, SEC filings show.

"Nothing is more important to Merck than the safety of its medicines and the patients who use them," Ronald Rogers, a spokesman for New Jersey-based Merck, said in an email. "We stand behind the safety and efficacy profile of Fosamax, and we encourage patients who have any questions about their health to speak with their physician."

Rogers said four lawsuits involving Fosamax have gotten as far as a verdict. Merck won three of those cases and lost one.

"It turns out that this pharmaceutical that is, supposedly, to protect women from osteoporosis, actually, after long-term use, makes bones more brittle," said Honolulu attorney Gary Galiher, of Galiher DeRobertis Ono, who is representing Takamori in the suit. "One of the strongest bones in the body looks like it got run over by a truck with just a minimal movement that wasn’t traumatic. It turns out these fractures are happening amongst middle-age women across the country. It’s been devastating what’s happened to (Takamori); her life’s been turned upside down. It’s just horrific."

The U.S. Food and Drug Administration issued a safety warning last year about atypical thigh-bone fractures possibly being associated with the long-term use of Fosamax and required a warning label to be added to the product, the law firm said.

Galiher said Takamori’s suit is the first Fosamax suit in Hawaii. There are 40 similar cases pending in 14 districts across the nation, he said.