TRENTON, March 12 (AP) — Merck & Company’s painkiller Vioxx contributed to an Idaho postal worker’s heart attack, a jury in Atlantic City ruled Monday, reversing the verdict in the man’s first trial and awarding him and his wife $20 million in damages.

The verdict was returned in the case of Frederick Humeston, who was granted a second trial in light of new evidence. Merck has now won nine cases and lost five in the mushrooming litigation over Vioxx, formerly a blockbuster arthritis pill.

Mr. Humeston, 61, of Boise, Idaho, suffered a heart attack in September 2001, several months before Merck, under pressure from federal regulators, put a stronger warning about the cardiovascular risks of Vioxx on the drug’s detailed package insert.

Mr. Humeston had taken Vioxx intermittently for knee pain from a Vietnam War shrapnel wound.

The five-man, three-woman jury ruled on March 2 that Merck was negligent and did not provide adequate warning about the risks before Mr. Humeston’s heart attack. That set the stage for a second phase of the trial, with the jury last week hearing evidence on whether Vioxx contributed to Mr. Humeston’s heart attack, entitling him to damages.

The jurors awarded Mr. Humeston $18 million in compensatory damages and gave $2 million to his wife, Mary.

A third phase of the trial will now begin, with jurors considering whether to assess punitive damages against Merck.

Mr. Humeston lost his first trial against the pharmaceutical giant in 2005, but Judge Carol E. Higbee of New Jersey Superior Court granted him a second trial because new evidence surfaced that short-term Vioxx use could also be risky; Mr. Humeston took the drug on and off for about two months. Merck insists Vioxx did not increase cardiac risks until after 18 months of use, but many doctors say research disproves that.

Merck, based in Whitehouse Station, N.J., removed Vioxx from the market in September 2004 after its own research showed the drug doubled the risk of heart attack and stroke.