U.S. health regulators, eyeing whether new rules are needed for Internet-delivered information on drugs and medical devices, will hear from companies and consumer groups at a two-day meeting that starts Thursday.

The Food and Drug Administration is gathering opinions on whether drug advertising on the Internet needs special oversight.

The Pharmaceutical Research and Manufacturers of America industry group has already said it will urge the FDA to adopt a safety logo on Web content that would link to FDA-approved information about a drug or device.

The topic has struck a nerve. About 900 guests tried to register for the event, to be held in a meeting room in Washington D.C. that only fits 350 people.

Presenters include an array of drug companies such as Pfizer and Eli Lilly, but also Internet heavyweights like Google and Yahoo.

"How most consumers collect and interpret health information has changed," said James Heywood, chairman and co-founder of PatientsLikeMe.com, a patient networking site.

The FDA announced the meeting, called the "Promotion of Food and Drug Administration-Regulated Medical Products Using the Internet and Social Media," in September.

Among questions the FDA asked presenters to address was: what criteria should be used to determine when third-party conversations are subject to "substantive influence" by companies that market the products being discussed.

"How do you control that advertising disguised as consumer information or consumer opinion?" asked Diana Zuckerman, president of the National Research Center for Women and Families, who will speak at the event.

Craig Audet, a regulatory affairs executive with Sanofi Aventis, said the FDA might be able to adapt its television rules on marketing to the Internet.

"In a broadcast ad, much of it is done through verbal as well as visual," Audet said. "Through social media, you don't have that verbal, you tailor that through visual."