NEW YORK (AP) -- Shares of Merck & Co. and Schering-Plough Corp. fell to record lows Monday, as analysts warned new clinical data would cause sales of their blockbuster cholesterol drug Vytorin to fall further. The companies market Vytorin through a joint venture, but earlier this year, partial results from a clinical study showed that it was no more effective at limiting plaque buildup than Merck's Zocor, a drug that is already available in generic form. Full results of that study were released Sunday. Vytorin is a combination of Zocor and Schering-Plough's drug Zetia. Schering-Plough shares plunged as low as...