The run had to come to an end eventually. After days upon days of soaring to new heights, the Dow Jones Industrial Average (DJINDICES:^DJI) has finally come back down to earth with modest losses today. As of 2:20 p.m. EDT, the index has fallen 26 points, or 0.18%, after investors saw nothing but green for more than a week. Most stocks are falling today, but good news has shares of Merck (NYSE:MRK) surging. Let's get caught up on the news you need to know.

Big pharma's divergent fortunes
Merck is leading the Dow by a wide margin, gaining 3.1% so far. An independent safety panel today gave the company the go-ahead to continue its clinical trial evaluating the effectiveness and safety profile of cholesterol therapy Vytorin. The panel said it had no safety concerns with the drug, which produces $1.75 billion in annual sales. The trial will determine Vytorin's ability to combat heart attacks and other cardiac ailments in comparison to generically available Merck drug Zocor. With Vytorin's sales on the downswing since 2008, Merck investors are hoping for a lift.

Not all is sunny among big pharma players, however. Merck's rival Pfizer (NYSE:PFE) ranks among the worst in the Dow today with losses of 1.2%, fueled by the FDA's strengthening of a warning label on the company's antibiotic Zithromax. While the drug also has generic competition, it's nonetheless a blow to Pfizer as the FDA cautions that Zithromax patients face potentially fatal heart-related risks.

Today's leading laggard, however, is Caterpillar (NYSE:CAT). This industrial stock hasn't rewarded shareholders recently, falling more than 6% over the last month. Worries over China's slowdown and pullback on infrastructure spending have caught up with Caterpillar, as investors fear the world's second-largest economy could be in for slower growth than it saw in recent years. With Caterpillar and many of its rivals reliant on higher-growth emerging economies like China to compensate for the sluggish trends in advanced economies, a slowdown could be dire.

On the other side of the Dow, telecom stocks are keeping the index from having too bad of a day. Verizon (NYSE:VZ) and AT&T are up 0.9% and 0.3%, respectively. Verizon caught a boost today as rumors swirl that the carrier will sell an all-metal version of the Nokia Lumia 920 next month as the company's premier Windows Phone 8 device. Not to be outdone, AT&T is making investors happy as it begins taking orders for the new BlackBerry Z10 smartphone today. The company expects to ship the devices starting March 22 as the first offering of BlackBerry's new BlackBerry 10 operating system.

Fool contributor Dan Carroll has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.