Last week the markets sprinted higher, and the Dow Jones Industrial Average (DJINDICES:^DJI) climbed 261, briefly rising above the 15,000 mark. The S&P 500 also had a fantastic week, gaining 32 points, or 2.03%, to surpass 1,600. But after the bull run of the past five trading sessions, investors are taking it easy today. As of 12:45 p.m. EDT the Dow is flat, while the S&P 500 is up just 0.2%. The Nasdaq, which gained more than 3% last week, is once again the best performer today, up 0.4%.

Dow losers
Merck
(NYSE:MRK) is again trading lower today, down 1%. Merck ended last week as the worst-performing Dow component after it dropped 4.56%. Today's decline is simply in keeping with the recent slide after the company announced poor quarterly earnings and cut its forecast 2013 earnings by $0.15. Analysts have not begun bashing the company with downgrades, which may likely begin soon, but investors have certainly voiced their displeasure with the company by dramatically lowering the share price over just a few trading sessions.

Shares of Pfizer (NYSE:PFE) are down by 0.6% this afternoon despite the announcement that the company will soon begin selling its erectile-dysfunction medication online. Customers will still be required to have a prescription, but this may make it easier for individuals to get their medication regularly. This move has also raised concerns among other companies within the industry, because it will likely disturb the current distribution model. 

And to round out the health care industry losers today, shares of Johnson & Johnson (NYSE:JNJ) are down more than 1%. As with Merck, there is little news pertaining to the company today, but some have speculated that the high price-to-earnings ratio and recent run-up in share price are making some investors reconsider whether the stock has any more gas in the tank. Year to date, shares are up 21.1%, and for a company most consider to be a more stable, slow-growing organization, that price appreciation over such a short time frame is a little excessive. Today's pullback is likely just investors taking money off the table.

Fool contributor Matt Thalman owns shares of Johnson & Johnson. The Motley Fool recommends Johnson & Johnson. The Motley Fool owns shares of Johnson & Johnson. Check back Monday through Friday as Matt explains what caused the Dow's winners and losers of the day, and every Saturday for a weekly recap. Follow Matt on Twitter: @mthalman5513. 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.