Alright...I actually looked up the Furosemide on the FDA's website and guess what...The FDA approved Furosemide on July ! 1966...
According to the label Furosemide is a diuretic whose primary indication in peds and adults is edema related to congestive heart failure...The label reads.
"Lasix is indicated in adults and pediatric patients for the treatment of edema associated with congestive heart failure, cirrhosis of the liver, and renal disease, including the nephrotic syndrome. Lasix is particularly useful when an agent with greater diuretic potential is desired."
That's a good point and you may be right for cardiovascular medicine.
In cancer (which is what I know best these days; I stopped working on Lipitor when it went off patent) it is pretty routine to add novel MOA drugs to standard of care before they ever get approval for a specific indication.