FACTBOX-Five facts about Merck's Vioxx

April 15 (Reuters) - Merck & Co Inc. (MRK.N) pulled the arthritis pill Vioxx, which once earned it $2.5 billion a year, from the market in September 2004 after a study found it doubled the risk of heart attack and stroke in patients. By then, it had been used by some 20 million U.S. patients.

Following are five facts about Vioxx.

* On May 20, 1999, FDA approves Vioxx for the relief of osteoarthritis symptoms, management of acute pain and primary dysmenorrhea, or painful menstruation.

* On Sept. 27, 2004, Merck tells the U.S. Food & Drug Administration a study to see if Vioxx could prevent colon polyps showed twice the risk of heart attacks among patients taking Vioxx for 18 months as those who took placebos. Merck withdraws the drug three days later.

* In Angleton, Texas, on Aug. 19, 2005, a jury in the first Vioxx civil trial found Merck was liable for the 2001 death of a 59-year-old Vioxx user and awarded his wife more than $250 million.

* Since then, juries have decided in favor of Merck 12 times and in plaintiff's favor five times. One Merck verdict was set aside by the court and has not been retried. Another was set aside and retried, leading to one of the five plaintiff victories. Two mistrials remain unresolved.

* Merck agrees on Nov. 9, 2007, to pay $4.85 billion to settle most of the U.S. claims that Vioxx caused heart attacks and strokes. There were more than 26,600 lawsuits outstanding when Merck announced the settlement.

(Reporting by Julie Steenhuysen and Bill Berkrot; Editing by Maggie Fox and Bill Trott)