THE REAL MOST ACTIVE Merck Drags Dow, S&P 500 Down For Loss.(MAKING MONEY)

Byline: JONAH KERI

NYSE stocks edged lower Thursday, though a collapse by drug making giant Merck caused the decline. The Dow fell 0.6%, the S&P 500 less than 0.1%. The small-cap S&P 600 ticked up 0.1%.

*Merck plummeted 12.07, or 27%, to 33. The stock traded 145 million shares vs. its average daily volume of 5.3 million. The stock was by itself largely responsible for the day's higher volume on the NYSE.

Merck said it will withdraw its best-selling anti-inflammatory drug Vioxx, citing long-term risks of heart trouble and strokes.

The stock accounted for an 89-point loss on the Dow. Without Merck, both the Dow and S&P 500 would have posted gains for the day.

Elsewhere, J.C. Penney slid 0.53 to 35.28 on twice its normal trade. A Banc of America analyst trimmed third-quarter earnings forecasts for the discount department store chain, as well as several other retailers.

On the upside, materials stocks continued to show strength. After pulling back Wednesday, Tetra Nitrogen bounced back ...