Partial payments for people claiming withdrawn painkiller Vioxx caused heart attacks will go out starting Aug. 28 under the $4.85 billion settlement between drugmaker Merck & Co. and plaintiffs’ lawyers, the claims administrator said today.

Those payments will amount to about 40 percent of each plaintiffs’ estimated total payout, but it’s unclear how many people will be getting checks in the first batch going out.

The settlement, meant to end the bulk of personal injury lawsuits against Whitehouse Station-based Merck, was reached in November. Merck pulled Vioxx from the market on Sept. 30, 2004, after its own research showed the once-blockbuster arthritis pill doubled the risk of heart attack and stroke.

During the monthly status conference with the federal judge in New Orleans coordinating most of the massive Vioxx litigation, Orran Greer of claims administrator BrownGreer PLC said 49,954 eligible claimants have now registered for a settlement.

That amounts to more than 97 percent of claimants eligible for the settlement — well above threshold levels the company required for the deal to proceed — and most of the others cannot be located by their attorneys, Greer told U.S. District Judge Eldon Fallon.

Greer said Merck waived its right to walk away from the settlement on Aug. 4 and, over the next two days, deposited $500 million in one escrow account and gave the claims administrators a letter of credit worth up to $4.1 billion to cover payments to claimants.