The rise of serious heart risks in drugs that treat chronic conditions has become one of the FDA’s top worries and is changing how the agency weighs new meds, according to John Jenkins, director of the agency’s Office of New Drugs. And so the FDA is thinking about how to weigh possible side effects as more drugs used to treat diabetes, pain and other conditions also appear linked to heart attacks.

“That has been the biggest safety shift in the last few years, and it’s also, I think, a driver for a lot of the public concern about drug safety,” he tells Reuters. “There have been a string of products or classes of products where we’re now seeing concerns about increasing the risk of cardiovascular events.” He cited Glaxo’s Avandia diabetes pill, Novartis’ Zelnorm bowel drug and Merck’s Vioxx.

In the past, patients typically took meds when they were seriously ill and known side effects were often more unusual ones such as liver failure, Jenkins says. Those were easier to link to drugs because they were less common in the wider population where heart disease is a major condition. This is a growing concern now as more Americans take drugs long-term to treat high cholesterol, for instance.

“We are thinking about what the implications of these new data and these new findings are for all chronically used drugs,” Jenkins says, adding that the FDA is thinking about which types of drugs may need to have more research on heart side effects either before or after approval. “It’s changing how we look at how much data you need to get a drug approved,” and the FDA “might look at more requirements for large studies after approval.”

For example, the agency has not typically asked makers of rheumatoid arthritis drugs to present heart data from large clinical trials, but “patients with rheumatoid arthritis have an increased risk of cardiovascular disease, so we have to start thinking about those issues.” He adds that the FDA has not yet taken any steps to require such info.

The agency plans to give specific advice to drugmakers about what kinds of data they will need to sell diabetes meds in the US, and Jenkins says recommendations will be released very soon. In July, an FDA panel recommended drugmakers should have to conduct long-term studies of cardiovascular effects or provide equivalent evidence to rule out an “unacceptable” risk of heart problems.