Yesterday, Pfizer Inc. took the doctor and inventor of the artificial heart off the mound as pitchman for the world's best-selling medication, after his credentials - in medicine and in his own exercise regimen - came under fire.

In the ads, which began their heavy rotation on television and in print in 2006, Jarvik touts the benefits of Pfizer's cholesterol-lowering drug. As of yesterday afternoon, Jarvik's photo still appeared on Pfizer's Web site advertising the drug.

But House Democrats said the ads could be misleading to consumers because Jarvik appeared to be giving medical advice, even though he is not licensed to practice medicine. While Jarvik holds a medical degree, he did not complete the certification requirements to practice medicine.

Democratic Reps. John Dingell and Bart Stupak, both of Michigan, said yesterday that the company had made the right decision.

"When consumers see and hear a doctor endorsing a medication, they expect the doctor is a credible individual with requisite knowledge of the drug," Stupak said.

In January, the lawmakers had asked Pfizer to hand over all records of its contract with Jarvik as part of a larger investigation into celebrity endorsements of prescription medicines.

Lipitor ad scrutiny intensified earlier this month when the New York Times reported that Pfizer had used a stunt double in an ad in which Jarvik appeared to be rowing. The company replaced that ad with one showing Jarvik jogging with his son.

"You add up the medical questions and the rowing questions, and it's a pretty damning indictment," said Bill Trombetta, a professor of pharmaceutical marketing at St. Joseph's University. "It made sense for them to cut their losses and move on."

Lipitor posted sales of more than $12 billion last year.

In a statement yesterday, Pfizer president of operations Ian Read said: "The way in which we presented Dr. Jarvik in these ads has, unfortunately, led to misimpressions and distractions."

Read said the company would provide "greater clarity in our advertising regarding the presentation of spokespeople."

Pfizer said it planned to launch a new Lipitor campaign in coming weeks, but it did not provide details. The company spent $118 million on Lipitor advertising in the first nine months of 2007.

In his response to initial questions about his qualifications, Jarvik issued a statement in mid-January in which he said he was neither a clinical doctor nor a celebrity but had the expertise to endorse Lipitor as a treatment against heart disease.

The use of celebrities in drug advertising has declined since reaching a peak in the late 1990s, said professor Michael Montagne of the Massachusetts College of Pharmacy.

At that time, Pfizer enlisted former senator and presidential candidate Bob Dole to pitch Viagra and rival Merck & Co. Inc. paid Olympic skating champion Dorothy Hamill to appear in ads for Vioxx.

"Much of the direct-to-consumer advertising we see today doesn't use celebrities because they are viewed as being a deceptive argument," said Montagne, who studies drug marketing.