Pfizer Hikes Warning on Bextra Skin Risk  NEW YORK (Reuters) - Pfizer Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=PFE.N target=/stocks/quickinfo/fullquote"&gt;PFE.N&lt;/A&gt; on Friday said two  clinical trials showed patients taking its anti-inflammatory  drug Bextra had a higher risk of cardiovascular events during  high-risk coronary bypass surgery.