Merck & Company Incorporated’s board has adopted a new severance plan aimed at preventing executives from jumping ship from the troubled pharmaceutical giant by offering big payouts if a future merger or change of control forces them out.

Whitehouse Station, N.J.-based Merck disclosed the plan in filings yesterday with the Securities and Exchange Commission.

The company’s problems include legal liabilities estimated at up to $18 billion since recalling its widely used arthritis drug Vioxx over increased heart attack risk.

The severance plan offers 230 key executives perks including up to three times their base salaries and bonuses if they are terminated due to a change of control.

For all but the 4,800 union workers at the 61,500-employee company, the plan would immediately vest all outstanding stock options and restricted stock units upon a change in control. The plan does not include performance based stock options that key research and development staff hold.

“The whole idea is to try to both retain and motivate employees during what we would call periods of uncertainty that might occur in connection with a rumored or actual change in control,” a Merck spokeswoman, Janet Skidmore, said yesterday.

Ms. Skidmore said the company’s board adopted the plan after a periodic review of Merck’s compensation and benefits package showed a gap, compared with other major companies.

“About 90% of large U.S. companies and nearly all other pharmaceutical companies have some form of change-of-control protection,” she said, adding that about two-thirds guarantee senior management change-in-control severance pay.

Ms. Skidmore would not discuss whether Merck officials are negotiating any mergers, acquisitions, sales, or other changes.

“The adoption of this program in no way implies that a merger or acquisition is imminent or desired,” she said.

Independent pharmaceuticals analyst Hemant Shah of HKS & Co. in Warren, N.J., agreed that such provisions are typical and said the board’s decision is “really inconsequential.”

Mr. Shah said implementing the new severance program doesn’t indicate any Merck deals are in the works.

“A potential acquirer is going to have a tough time evaluating the company,” he said, because of the uncertainty over the cost of the Sept. 30 Vioxx recall.

The SEC filings define a change in control as a merger, consolidation, or reorganization bringing a significant shift of board members or shareholders; liquidation or dissolution of Merck, or sale of substantially all of its assets; a significant change in the composition of the board of directors, or anyone acquiring more than 20 percent of Merck’s voting shares.

The plan was adopted during a board meeting November 23. Its provisions would cover a two-year period following any change of control, during which time the plan could not be changed to reduce the severance benefits.