After reading this article I remain in a state of disbelief.

F.D.A. Says Millions Got Unapproved Nitroglycerin – NYTimes.com

The problem of the unapproved tablets stems from a longstanding ambiguity about the rules for drugs whose use predates the establishment of the F.D.A. in 1938. Only one brand of nitroglycerin pills is federally approved: Nitrostat, made by Pfizer, on the market since 2000.