Alpharma Starts Generic of Pfizer Drug  CHICAGO (Reuters) - A generic version of Pfizer Inc.'s  &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=PFE.N target=/stocks/quickinfo/fullquote"&gt;PFE.N&lt;/A&gt; \$3 billion epilepsy treatment Neurontin is set to hit  the U.S. market after Alpharma Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=ALO.N target=/stocks/quickinfo/fullquote"&gt;ALO.N&lt;/A&gt; said on Friday it  will sell the cheaper version.