Avandia (rosiglitazone) is a drug used by many with type 2 diabetes and is designed to make the body more sensitive to insulin.
The warning says the diabetes drug could cause chest pain or heart attacks.
The FDA says drug company GlaxoSmithKline will conduct a trial comparing Avandia with another rival drug Actos produced by Takeda in order to establish if the risks are unique to Avandia.
The study which will begin next year, will not be completed until 2014, but the FDA will review the data as the study progresses for any indication something is amiss.
Doctors are being advised to closely monitor patients taking Avandia for any heart effects.
The FDA says it is allowing Avandia to remain on the market because the evidence of the risk for heart attack or cardiac ischemia, though higher than for other type-2 diabetes drugs, is inconclusive.
The FDA says studies already conducted which appear to show a risk, compare Avandia to a placebo; the top-selling diabetes drug has been under scrutiny since a U.S. analysis last May linked it to a 43 percent higher risk of heart attack in patients.
Glaxo's chief medical office Dr. Ronald Krall, says Avandia remains a safe and effective medicine for most patients with type-2 diabetes when it is used appropriately.
FDA officials insist they carried out a comprehensive consultation process before allowing Avandia to remain on the market.
Apparently two different advisory committees took part in the decision making and a very broad range of opinions were considered.
The FDA says drugs such as Avandia were not meant to reduce the heart risks caused by diabetes.
In 2006 Avandia was Glaxo's second-biggest seller with sales of $3 billion.
The findings further tie together the 24-hour cycle of the body with metabolic function. Circadian rhythms are our sleep-wake cycle and metabolism is how we process food, so it makes sense that there would be biological cross-talk between the body's 24-hour rhythm and metabolic function, says Lazar. Indeed, scientists already recognize that getting too much or too little sleep increases the risk of diabetes. The newly discovered circadian/metabolic link could be the focus of a new generation of diabetes treatments.
The Penn group worked with scientists at GlaxoSmithKline, who demonstrated that the Rev-erb protein can physically bind to heme in the test tube. The Penn scientists then found that heme, by regulating the activity of Rev-erb, reduces the amount of glucose produced by liver cells.
What's exciting about this is that it puts heme in a central role in the metabolic regulation of the cell, says Lazar. Not only is it a key component in making energy, but also in the pathway for turning off glucose production. Excessive glucose production by the liver is a major cause of high blood sugar in diabetes.
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