(Adds impact, panel member quote, paragraphs 2-3; also adds analyst comments, detail, background)
SILVER SPRING, Md., July 2 (Reuters) - U.S. regulators should require drugmakers to study the potential heart risks of all new diabetes medicines, an advisory panel said on Wednesday.
The recommendation could force companies to run longer and more expensive studies and delay new entrants in a $6 billion U.S. market that was hit last year by concerns surrounding GlaxoSmithKline PLC's (GSK.L) diabetes pill Avandia.
"Although it might be a little more burdensome ... we need more studies," said Dr. Clifford Rosen, a panel member and endocrinologist at the Maine Center for Osteoporosis.
Now, companies generally need to show only that their medicines lower blood sugar levels. That approach is inadequate for patients, panel members said.
The group of outside experts that advises the Food and Drug Administration voted 14-2 to recommend companies do a long-term study of cardiovascular effects or provide equivalent evidence to rule out an "unacceptable" risk of heart problems.
Studies need to last as long as five years to detect heart attacks, strokes and other problems, several panel members said. Many endorsed the idea of starting the study before approval and completing it after a drug reaches the market.
The requirement should apply to all experimental drugs even if they show no signs of concern in early testing, the committee said.
"That's a shift in expectations of what we are asking for. It's a higher level ... of assurance that you've excluded cardiovascular risks," said Dr. John Jenkins, director of the FDA's Office of New Drugs.
Some drugs already on the market also may need more study of cardiovascular safety, panel members said.
The FDA will decide what rules to impose on companies but usually follows panel recommendations.
Diabetes medicines are among the biggest selling drugs. U.S. sales of the leading medicines exceeded $6 billion in 2007, according to healthcare information company IMS Health.
Several drugmakers, including Glaxo, Bristol-Myers Squibb Co (BMY.N), AstraZeneca Plc (AZN.L), Eli Lilly and Co (LLY.N) and Amylin Pharmaceutical Co AMLN.O, are working to bring new diabetes drugs to the market.
If the FDA sets strict requirements, "you're going to see increased research and development budgets, and you're probably also going to see less development in diabetes," said Morningstar analyst Damien Conover.
Higher standards could help Merck & Co Inc (MRK.N) by delaying rivals to its fast-selling drug Januvia, Conover said.
Nearly 24 million Americans have diabetes, the U.S. government estimates. Most cases are type 2 diabetes, which experts link with obesity, poor diet and lack of exercise.
Diabetics produce less insulin, or their bodies use it less effectively, which makes blood sugar rise. That can damage blood vessels and organs, leading to blindness, kidney disease, limb loss and heart disease.
Experts agree blood-sugar control helps prevent complications such as damage to the eyes and kidneys. But no conclusive evidence exists that any diabetes drug reduces heart disease, the top killer of diabetics, FDA officials said.
Concern that diabetes medicines may damage the heart arose last year when a study by Cleveland Clinic researchers found Glaxo's Avandia increased the chances of a heart attack.
Glaxo has said Avandia's safety is comparable to similar pills. But the company agreed to add a strong warning that the drug might increase heart attack risk with a note that the data was inconclusive. Studies of cardiac effects are continuing. (Reporting by Lisa Richwine and Susan Heavey; editing by Tim Dobbyn)