Furosemide(Lasix) is the most powerful and most widely used diuretic drug in the world. The injectable version is fast-acting, and dries someone out like prune. Its used in the medical field, mostly in the emergency room, to purge people who have ingested large doses of toxins, hoping that the toxins can be excreted before they enter the system and so avoiding worse problems. It also makes a good shock treatment for people who are admitted with dangerously high blood pressure. Its very multi-functional, but its also a very dangerous drug. It signals the body to immediately excrete both intracellular and extracellular water, and with it the key electrolytes sodium and potassium. This can lead to severe problems. Muscle contraction is based on the exchange of electrolytes. That means in first instance an electrolyte imbalance can causing cramping and other irregularities in muscle contraction. Now if its only a calf or a bicep, no harm done in the long run. But when its your heart muscle, that's another story. In 1985 professional bodybuilder Mohammed "Momo" Benazziza fell dead after winning a Grand Prix, the cause of death was believed to be his pre-contest use of the diuretic Lasix.
In most sports diuretics are used to lose small amounts of weight in a hurt. If you compete in weight classes and need to drop a pound in an hour, lasix will do the trick for you. Cleans the water from your body and you are lighter. If you have a match the next day, you are probably heavier again, so a major advantage. In bodybuilding the use of diuretics is for another reason entirely. The aim is after all to show as much muscle as possible, and to show as much definition and striation within that muscle. Unfortunately even at the dangerously low body-fat percentages bodybuilders compete at, a lot of that definition may still be hidden under layers of subcutaneous water. By using diuretics, that water can be shed and the maximum potential of a physique can be retained. In many cases, the levels of water retained by an athlete has made the difference between doing very well and doing very poorly. And the differences in the water household between the pre-judging of a contest and the evening show have sometimes made the difference between several placings. So diuretics have become an integral part of bodybuilding over the last 20 years.
Furosemide comes in oral tablets of 20 and 40 mg and in an injectable form. The injectable is the most potent. Its injected intravenously, as opposed to most steroids which are injected intramuscularly. It can become active in a matter of minutes and has a drastic effect. But as described previously, also a very dangerous one. The orals will usually take 60-90 minutes to kick in, but have a fairly drastic effect themselves. Furosemide is without a doubt the most potent diuretic in the world. An athlete will rarely opt to take more than 40 mg daily, and only in the last 4 or 5 days leading up to a show. The Injectable version is only used pre-contest, especially if there is testing. Testing for diuretics has become very popular in bodybuilding of late, and that has driven more athletes to wait until after taking their piss, and then inject some Lasix to get rid of the last bit of water. Needless to say this is a reckless practice. If a stronger effect is required, athletes are more likely to opt for adding another, milder diuretic like spironolactone (Aldactone), instead of increasing the dosage of lasix. There are a number of combination diuretics like Lasilactone that enjoy great popularity in the sports sector. Usually they near the potency of using twice as much lasix, but with much less hazard.