US STOCKS-Wall Street falls after strong week, Pfizer and Allergan drag
* Pfizer, Allergan drop after biggest-ever healthcare deal
* Energy stocks helped by Saudi move to stabilize prices
* Alcoa up as Elliott takes stake
* Indexes down: Dow 0.15 pct, S&P 0.12 pct, Nasdaq 0.02 pct (Updates to afternoon, adds commentary changes byline)
By Sinead Carew
Nov 23 (Reuters) - U.S. stock indexes turn negative in afternoon trading on Monday after a week of strong gains, while a record healthcare deal failed to impress investors.
After a week when S&P 500 had its best performance of the year, investors were also unimpressed by Monday's economic data and some were concerned that economic growth may be slower than expected and holiday season sales may disappoint, said Stephen Massocca, Chief Investment Officer of Wedbush Equity Management LLC in San Francisco.
"We had a very large rally last week and it's not surprising to see the market correct after that," said Massocca.
The Dow Jones industrial average fell 26.95 points, or 0.15 percent, to 17,796.86, the S&P 500 lost 2.47 points, or 0.12 percent, to 2,086.7 and the Nasdaq Composite dropped 1.15 points, or 0.02 percent, to 5,103.77. Continuación...