TRENTON, N.J. — A surge of lawsuits has swamped courthouses just ahead of the two-year anniversary of drugmaker Merck & Co. pulling its blockbuster painkiller Vioxx from the market.

Today is the deadline for many users to sue the Whitehouse Station, N.J.-based drugmaker over heart attacks, strokes or other harm they blame on Vioxx. Patients in 22 states, many heavily populated ones, can no longer sue Merck because they have a limit of two years on initiating personal injury lawsuits; four other states have one-year limits.

Merck is holding its own defending Vioxx in the courtroom, racking up its fifth win this week. Most experts say Merck's fight-every-case strategy is discouraging an even bigger flood of suits, although each trial is costing millions.

So far, well over 21,700 suits, many with multiple plaintiffs, have been filed, up sharply from the 14,200 Merck reported as of June 30. Merck also has at least 5,800 agreements waiving the statute of limitations for other Vioxx users.

The company faces at least 190 potential class-action suits by Vioxx users and Merck shareholders. Merck is challenging the one class action already approved, for health insurers and unions seeking to be reimbursed for Vioxx they bought for health plan members — a case that could cost Merck $15 billion if it loses.

In New Jersey, which has a two-year limit for both types of suits and has the most cases because it's where Merck is based, more than 6,500 cases have been filed since June 30. By Wednesday, 13,624 Vioxx cases had been recorded in Atlantic County Superior Court.

In New Orleans, where federal lawsuits are being coordinated by U.S. District Judge Eldon Fallon, about 950 new cases have been filed since June, for a total of 6,650. Court personnel said filings picked up strongly in September.

Despite the Vioxx hangover, Merck's financial performance has improved amid cost cutting and strong sales of key drugs, including asthma/allergy treatment Singulair and cholesterol drugs Vytorin and Zetia. Three new vaccines were approved this year, one of them the world's first to prevent cervical cancer. The stock price has recovered to within a couple dollars of its $45 level the day before the Sept. 30, 2004, Vioxx withdrawal.

"If you compare the company's focus and energy and morale with where we were two years ago, the focus and energy is back," Merck Chief Executive Officer Richard T. Clark told The Associated Press. "What's really important is that the company internally is focusing on our mission ... putting patients first and scientific excellence and business excellence."