Pfizer Profit Up on Demand for Key Drugs  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;, the world's  biggest drugmaker, on Wednesday said third-quarter earnings  rose on higher sales of key medicines and favorable foreign  exchange factors.