But many viewers fail to retain critical information about the drug and possible side effects, the study also found.
TV commercials for prescription drugs have become commonplace since the Food and Drug Administration set up rules and made them legal in 1997.
The ads, which show allergy sufferers dancing through fields of flowers or doctors recommending antacids to dyspeptic taxi drivers, are controversial. Drug companies maintain they educate and get people to doctors but consumer groups say they profit only the advertisers.
The report, funded by The Kaiser Family Foundation, found that the pervasive ads have a considerable effect - nearly a third of adults have talked to their doctor about a drug they saw advertised. About 44 percent of those adults then received a prescription for the drug they saw advertised.
Viewers sometimes miss or forget important information, said the study, which was released Thursday.
After watching a commercial for an asthma drug, about a quarter of viewers came away with the mistaken impression that there are drugs that can be used to replace an asthma inhaler.
Some consumer groups have complained that the ads encourage Americans to believe they know what drugs are best for them - pressuring their doctors unnecessarily.
"We have people seeking out drugs that are not necessarily right for them and sometimes asking for the most expensive drug on the market, even though there may be generic drugs that accomplish the same thing," said Ron Pollock, executive director of the
Washington-based consumer group, Families USA. "The high costs of the ads are causing companies to raise drug prices and health care providers to raise service prices."
Drew Altman, president of the Kaiser Foundation, said the benefits of the commercials outweigh any price increases.
"Drug ads may drive up health care costs and drug company profits, but the drugs people get may also make them healthier," Altman said.
Drug companies spend a lot on the ads -- more than twice on marketing and promotion overall than on research and development, the foundation said.
"Last year alone, the pharmaceutical industry spent $2.5 billion on all forms of 'direct-to-consumer' ads," the foundation statement said.
This is a nine-fold increase from $266 million in 1994.
The study also found that doctors are still more likely not to prescribe a drug a patient asked about because of a TV ad.
In 35 percent of the cases, the doctor suggested a change in lifestyle. About a quarter of the time, the doctor prescribed a different drug.
Christopher Molineaux of Pharmaceutical Research and Manufacturers of America (PhRMA) said the survey confirmed that the ads increase awareness of diseases and prompt people to seek treatment who might otherwse put off seeing a doctor.
"Consumers are now asking questions. They are evaluating information. They are making decisions," he said.
Dr. Sharon Levine, associate executive director of the Permanente Medical Group, said this may be so, but said the survey showed that people quickly forget any information they have gleaned from the ads.
"Most of direct-to-consumer advertising is promotional. It does what it is expected to do -- it raises brand awareness ... but it does not educate," she said.
The study was conducted by interviewing 1,872 people who watched a series of commercials for prescription drugs and 639 other people. The margin of error was plus or minus 2.6 percentage points.
© MMI, CBS Worldwide Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press and Reuters Limited contributed to this report