Patent problems at Pfizer

Pfizer's patented Lipitor is expected to face tough competition from generic versions of Merck & Co.’s cholesterol-fighting rival, Zocor, and Bristol-Myers Squibb Co.’s Pravachol. Plus, Vytorin, the product of a joint venture between Merck and Schering-Plough Corp., is also performing well.

In 2006, Pfizer will lose patent protection on antidepressant Zoloft, which booked $3.3 billion in sales last year. Last year it lost exclusivity on blockbuster antibiotic Zithromax while pain reliever Neurontin faced generic competition in 2004. [AP]