New Jersey's Supreme Court rejected a huge class-action lawsuit against drugmaker Merck & Co.(MRK) over its withdrawn painkiller Vioxx on Thursday, reversing two previous lower-court decisions.

The suit was brought by a union health plan on behalf of all insurance plans that paid for Vioxx prescriptions. A lawyer for the New Jersey union says the case could be worth more than $15 billion if Merck loses.

The Whitehouse Station-based company pulled Vioxx from the market three years ago after research showed it doubled risk of heart attacks and strokes.

Lawyer Chris Seege has argued that if Merck had disclosed those risks earlier, prescription plans would have favored other painkillers.

A state judge and then an appeals court approved the class action, but Merck appealed to the New Jersey Supreme Court, which ruled a nationwide class is not appropriate.

Merk shares rose 16 cents to $49.56 in early trading.