The task of keeping diabetes in check has gotten harder. While rosiglitazone, GlaxoSmithKline's (GSK) Avandia, lowers blood-sugar levels, it also increases the risk of heart attack 42% and doubles the risk of heart failure, according to a study in the Journal of the American Medical Association. Other ongoing research, however, does not show such an increased risk. Even so, the FDA has issued a warning label alerting users to increased danger of heart attack, and Canadian officials have restricted the drug to those with hard-to-control blood sugar. GSK will issue a pamphlet explaining the warning and will begin a study next year to compare Avandia with other diabetes drugs.