When a Stock's Cash Cow Dies

The pharmaceutical giant Merck & Co. pulled its star product, Vioxx, off the market after a study confirmed concerns about increased chances of heart attack or stroke. Doctors use Vioxx with sales of over $2.5 billion last year to treat arthritis. Merck stock (MRK - NYSE) plunged on the news. This is an example of what happens to a stock when a major product becomes a major liability.
Read the latest report from Reuters.
For more information of how other events effect stock prices, read my article Why the Market Rises and Falls.