WASHINGTON (AP) -- Diabetes drugs would be subject to more stringent safety standards that could cost manufacturers millions, under recommendations made Wednesday by a government panel.

Advisers to the Food and Drug Administration voted 14-2 that all new diabetes drugs should undergo longer studies to assure they don't increase risks of heart problems.

The opinions from diabetes experts, cardiologists and statisticians come less than a year after the FDA was criticized for its handling of heart risks connected with a widely used GlaxoSmithKline pill. The drug was approved in 1999 but the agency didn't add a warning about potential heart risks until last November.

The majority of the panel said drug companies could begin safety testing -- expected to take between five and seven years to complete -- before they submit drugs to the FDA and finish the studies after their release.

But at least one panelist doubted whether the proposed studies would actually uncover heart risks.

"If you wait this amount of time for testing you're going to be preventing certain drugs from getting out there that may be better than what we already have," said Dr. Eric Felner, a pediatric specialist at Emory University School of Medicine.

The FDA is not required to follow the panel's advise, though it often does.

If the recommendation is adopted, development of diabetes drugs would become longer and more expensive, since it can cost tens of millions of dollars to perform long-term studies that track heart problems in thousands of patients.

GlaxoSmithKline PLC, AstraZeneca and Novartis AG are among the companies developing diabetes treatments to compete in the domestic market, which grew to over $6 billion last year, according to pharmaceutical research firm IMS Heath.

Takeda Pharmaceuticals' Actos, GlaxoSmithKline's Avandia, and Eli Lilly and Amylin Pharmaceutical's Byetta currently dominate the U.S. market.

Nearly 24 million Americans have Type 2 diabetes, which can lead to kidney failure, blindness and heart disease.

The FDA was pressured to reconsider how it approves diabetes medications after an analysis released last year showed GlaxoSmithKline's blockbuster drug Avandia may increase patients' risk of heart attack.

The agency currently approves diabetes drugs based on their ability to lower blood sugar levels, since the condition is characterized by excessive blood sugar. But Dr. Steven Nissen, who authored the analysis on Avandia, said Tuesday that criterion has little value if drugs also increase heart problems.

The FDA is operating under "the irrational belief that lowering blood sugar using virtually any pharmacological means will produce" better results for patients, said Nissen, who is chairman of cardiology at the Cleveland Clinic.

He recommended the FDA require drug companies to prove their drugs do not have significant heart risks before granting approval. After the drugs are on the market, companies would be required to complete large, multiyear studies to confirm their safety.

FDA scientists and outside researchers have warned that saddling companies with additional safety requirements could slow the development of new medications.

"The fallacy here is that we will never know everything we'd like to about a drug before it goes on the market," Dr. Ray Woosley, president of the Critical Path Institute in Tucson, Ariz., said in a phone interview Tuesday. "If we held up drugs until we did know everything a lot of people would die."

The institute is a nonprofit partnership with the FDA that aims to speed up the development of new drugs.

Approving drugs based on biological measurements, like blood sugar levels in diabetics, is thought to be a promising method for speeding-up drug development because the results can be gathered relatively quickly. But that approach is under scrutiny, as some lawmakers and medical experts believe the FDA should not approve drugs without evidence they improve more meaningful measures like increasing patients' life span.

Sen. Charles Grassley, R-Iowa, is investigating the FDA's approval of Avandia and another drug Vytorin, which was also cleared based on biological test results.

The agency approved Vytorin, jointly marketed by Merck & Co. Inc. and Schering-Plough Corp., based on its ability to lower bad cholesterol, which is widely believed to reduce heart attacks and deaths.

But a study released in January showed Vytorin was no more effective at limiting deadly plaque buildup than a low-cost generic drug.

Since then, the FDA has denied approval of another highly anticipated cholesterol drug from Merck, prompting speculation by analysts that the agency is raising approval standards for those medications. The FDA has not said whether such changes are in the works.

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