That, of course, reflects the medical issues facing audiences that skew older.

“The drug companies aren’t generally marketing to people in their 30s; they’re marketing to the 65-plus, and that’s the population that tends to still be watching television,” said Allen Adamson, a brand strategy consultant.

And when the ads come on, that audience is also listening intently to all that can befall them if they take a certain drug. An unexpected side effect of ad agency compliance with the drug administration’s regulation, it turns out, is enhanced credibility.

“It’s counterintuitive, but everything in our research suggests that hearing about the risks increases consumers’ belief in the advertising,” said Jeff Rothstein, the chief executive officer of Cult Health, an ad agency that specializes in health care.

As Howard Courtemanche, president of the health and wellness practice at Young & Rubicam, put it, “What is seemingly a negative to people who don’t have a condition or disease is a positive to people who suffer from it because they’re thinking, ‘Well, of course it has side effects. It’s fighting a really serious illness.’ They’ll say, ‘I’m in a life-or-death situation and I want a drug that’s really strong. I expect there to be risk to get the rewards.’ ”

Still, that interest goes only so far.

“At some point, the side effects become white noise,” said Maryann Kuzel, who oversees analytics at Publicis Health, a unit of the communications company Publicis Groupe. “There’s a huge amount of information compressed into a 60-second commercial, more so than any other industry.”

“You have the benefits of the drug,” she said. “You have the specific patient population the drug is intended to treat. You have the dosing mechanism. Is it oral or is it an injection? Where is it administered? How frequently do you need to take it? And, of course, you have all the side effects. And we know that consumers are multitasking across multiple devices while they’re watching TV. So comprehending all that information is a tall order for consumers.”

There may be a cure for that. This year, the F.D.A. released a study suggesting that a shorter list of side effects including only those that the agency described as “serious and actionable” helped people remember a drug’s risks and benefits.

“The regulation is still that we have to give all the risks in the TV ads, ” Ms. Kuzel said. “But because of this new research, the door might be a little open for us to start offering proposals of how we might communicate to consumers better.”