Arthritis Drug Vioxx Being Pulled  NEW YORK (Reuters) - The arthritis drug Vioxx, used by 2  million people around the world, is being pulled off the market  after a study confirmed longstanding concerns that it raises  the risk of heart attack and stroke, the manufacturer, Merck    Co. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=MRK.N target=/stocks/quickinfo/fullquote"&gt;MRK.N&lt;/A&gt;, said on Thursday.