An experimental diabetes drug that may increase the risk of congestive heart failure and death should not be allowed on the market despite initial support from U.S. regulators, a consumer group said on Monday. Public Citizen’s Health Research Group called on the U.S. Food and Drug Administration to hold off approving Pargluva, made by Bristol-Myers Squibb Co. and Merck & Co Inc., without “at the very least” a five-year clinical safety study. The fate of the drug, know generically as muraglitazar, is already unclear.