Lipitor's importance to its maker, Pfizer (PFE - Get Report), is readily apparent -- not only is it the company's biggest product, it's also the world's top-selling prescription drug. The continuing challenge is beating back increasingly fierce competition.
"Pfizer is in a tough spot," says Joseph Tooley of A.G. Edwards. "Generic Zocor is a game-changer. It's growing at a rapid pace."
For the four weeks ended June 1, Lipitor had a 32.7% market share of U.S. prescriptions, down from 40.9% a year earlier. Generic Zocor now has a 23% share, according to a recent report from Tooley's firm, citing data from the medical-products-tracking firm IMS Health.At the same time, Lipitor's dominance is shrinking while the total market is growing. U.S. prescription volume rose 10.3% in the past year, but Lipitor's volume dropped 12%. Pfizer has regained a tiny amount of lost prescriptions thanks to Caduet, which combines Lipitor and the blood-pressure drug Norvasc. Still, Caduet's market share is up to only 1.6% from 1.2% a year ago. "Caduet appears to be gaining some traction," says Tooley, noting that the drug remains a small player. Tooley, who doesn't own shares, has a hold rating on Pfizer. His firm has had a recent noninvestment banking relationship with the drugmaker. Click here for TheStreet.com TV video of this story.