What price? If Medicare's new discount drug card Web site isn't confusing enough, stay tuned. Agency administrator Mark McLellan has announced that the site, www.medicare.gov, which already carries prices for brand-name, generic and mail order drugs, will soon add prices for "alternative drugs within a therapeutic class." That means drugs that have similar effects to those prescribed, though they may work by a different mechanism. Four weeks ago a Medicare spokesman predicted the change would occur within a week; last week he said it could happen in the next few weeks.

Who cares? You may. Many insurers have suggested so-called therapeutic alternatives for years because they are often cheaper. WellPoint, for example, a company planning to merge with Anthem to become the largest U.S. health insurer, lists Prozac (fluoxetine) as a therapeutic alternative for top-selling antidepressant Zoloft. Medicare's recent prices for a 30-day supply of generic fluoxetine were as low as $4.78 retail and $1.34 mail order (based on a 90-day supply) vs. $72 for a 30-day retail supply of Zoloft.

What concern? But Stephen Peterson, chairman of the psychiatry department at Washington Hospital Center, says that the drugs are not always interchangeable. Fluoxetine, unlike Zoloft, can interact with drugs for heart disease, which many older people take. And allergic reactions are far more common with fluoxetine than with Zoloft, he said.

Even some insurers admit concerns. "We recommend patients have a thorough conversation on the pros and cons when discussing therapeutic alternative drugs with their doctor," said Sam Nussbaum, chief medical officer at Anthem. And even though Anthem offers lovastatin, a generic cholesterol drug, as an alternative for the statin Lipitor, he said, "we have also sent information to physicians showing them that Lipitor . . . is the best cholesterol drug for preventing heart attacks and lowering cholesterol levels."

-- Francesca Lunzer Kritz

Prozac: Instead of Zoloft?