Bumetanide is a loop diuretic of the sulfamyl category to treat heart failure. It is often used in patients in whom high doses of furosemide are ineffective. There is however no reason not to use bumetanide as a first choice drug. The main difference between the two substances is in bioavailability. It is said to be a more predictable diuretic, meaning that the predictable absorption is reflected in a more predictable effect. Bumetanide is 40 times more potent than furosemide (for patients with normal renal function).