Kos Sinks, Generic Drug Blamed  CHICAGO (Reuters) - Shares of Kos Pharmaceuticals Inc.  &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=KOSP.O target=/stocks/quickinfo/fullquote"&gt;KOSP.O&lt;/A&gt; slumped 8 percent on Thursday after an analyst  suggested Barr Pharmaceuticals Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=BRL.N target=/stocks/quickinfo/fullquote"&gt;BRL.N&lt;/A&gt; could launch a  copycat version of a key Kos drug earlier than expected.