Furosemide, usually sold under the trade mark Lasix(TM) is a diuretic drug used to treat congestive heart failure and edema, among other conditions. It is generally regarded as safe, but there is evidence that its use can damage hearing, and it can lead to higher levels of uric acid and gout. It also lowers potassium levels and can cause hypoglycemia.
It does have some medicine interactions with several medications, including aspirin and lithium.