Pfizer Inc. (PFE) expects to pay at least $772 million to resolve all of the product-liability litigation surrounding its hormone-replacement therapy drugs, but the ultimate tally could be higher.

Pfizer inherited much of the litigation through its 2009 purchase of Wyeth, maker of hormone-therapy drugs including PremPro, which treat conditions associated with menopause such as hot flashes.

Nearly a decade ago, government-sponsored studies began showing the drugs were associated with increased risk of breast cancer and other adverse events, which spurred thousands of lawsuits by women or their families claiming the drugs caused injuries.

New York-based Pfizer said in a filing with the Securities and Exchange Commission Thursday it had settled or struck agreements to settle about one-third of the hormone-replacement therapy cases against it, as of March 31.

The company booked charges of $172 million for the first quarter and $300 million in prior quarters to cover costs of those settlement actions, as well as verdicts against the company.

In addition, the company booked a separate charge of $300 million for the minimum expected costs to resolve all of the other outstanding cases against Pfizer. That amount could rise, however.

"The foregoing charges are estimates and, given the uncertainties inherent in product liability litigation, additional charges may be required in the future," said Pfizer spokesman Chris Loder.

One plaintiff's attorney says Pfizer's tally sounds like a conservative estimate.

"That leaves a lot of room for interpretation for what the maximum would be," said Tobias Millrood, who has represented women in the hormone-drug lawsuits. "With several thousand cases still unresolved the exposure remains large."

Pfizer didn't disclose how many cases remain outstanding. As of 2009, when stand-alone Wyeth last disclosed figures, about 9,900 women had cases pending against Wyeth.

Pfizer previously disclosed some details of the settlement charges in its earnings report earlier this month, but didn't specify the total minimum estimate for settling all of the cases.

Pfizer said it has prevailed in a majority of hormone-therapy cases that were set for trial, though it has lost some jury verdicts.