Spironolactone is used mostly as a diuretic. Because it inhibits aldosterone production it has a diminishing effect on water retention. Aldosterone is the hormone that regulates the amount of water a body stores, by increasing or decreasing electrolyte counts, such as the amount of sodium in the blood. Through its regulation of aldosterone, spironolactone can signal your body to release water. This is particularly useful to those in the modeling business, and to competitive bodybuilders. Lowering water retention can increase muscle definition, and make for a better showing. Athletes competing in weight classes are particularly fond of diuretics as well, because shedding a few pounds of water allows them to compete in their designated weight class, without having to sacrifice muscle tissue or go through the rigors of diet in order to lose fat.
In medical settings spironolactone can be used as a diuretic when toxins have been ingested, but for those things most physicians will opt for more drastic measures, such as intravenous injections of a more potent diuretic such as lasix (furosemide). Its very popular as an anti-hypertensive drug, since its aldosterone inhibiting effects will lower sodium retention and lower blood pressure that way. For these instances most physicians will actually prefer spironolactone or some type of combination diuretic, because its known as a potassium sparing diuretic. Some heavier diuretics will reduce intra-cellular water as well, and ravage the body's potassium stores. This can result in life-threatening conditions. Mohammed Benazziza fell to his death after his electrolyte balance was thrown out of whack by the use of intra-venous lasix. Since spironolactone has no such effect on potassium levels you do not need to supplement extra potassium or worry about your electrolyte balances. In fact, using more than 2 grams of potassium per day can be equally hazardous, whereas with lasix one would almost have to get 2-3 grams of potassium, additionally, per day.
Lately a lot of research has been done on using spironolactone as an anti-androgen. Since most competitors will use a diuretic for no more than 5-10 days, this needn't really concern us. It has also raised a lot of questions about whether or not spironolactone can therefore have a use for us in preventing hair loss, acne1 and prostate hypertrophy2, the most frequent of androgenic side-effects. So I would like to answer these questions here. The studies do indeed show that spironolactone can remedy some androgen-mediated conditions, and does so through other means than finasteride (proscar). Finasteride blocks the 5-alpha-reductase enzyme, which converts dehydro steroids to their more androgenic dihydro forms. Like converting testosterone to DHT. But the majority of steroids used, especially when cutting, are already dihydro forms and finasteride has no use, since the 5-alpha reductase enzyme no longer has effect on the androgenic potency. But spironolactone has been shown to work through other pathways3. Its steran nucleus would suggest that it binds the androgen receptor itself, but is not potent enough to, or structurally incapable of (I would opt for the latter) activating it. Its effect on androgens would comparable to the effect that clomid or Nolvadex would have on estrogens.
So what's the final verdict? It may have some use in reducing androgenic side-effects, but only because it blocks the androgen receptor. That means for every bit of side-effects you block, you will lose an equal amount of gains. That also mean to completely eliminate side-effects, you would completely eliminate gains, and might as well not take steroids at all, instead of wasting money on two products that cancel each other out. In short there is no way of preventing side-effects completely, and those people who fear side-effects more than they want gains, should still stay away from steroids altogether. Either you want the gains bad enough, or you don't. If you don't then don't touch the stuff. If you do, then you come to terms with the risk of side-effects.
That doesn't mean the anti-androgenic properties of spironolactone are completely useless to use. Using them post-cycle can be very effective. The aim is to get testosterone back online as soon as possible, and that means eliminating negative feedback. From estrogen first of all, through the help of clomid or Nolvadex, but also by eliminating negative feedback from androgens, and here spironolactone can help. Running it alongside HCG and then to the end of Nolvadex/Clomid treatment. The result is less side-effects from the HCG (acne, water retention), a synergistic effect with the Clomid/Nolvadex to reduce water retention and it stops the continuation of side-effects. Many times users of androgenic steroids will notice that hair loss continues or even starts after a cycle is done, especially with long acting injectable esters. That's too much, we don't have to tolerate more side-effects than what we need for optimal gains after all. And the spironolactone can prevent androgenic side-effects from continuing after the cycle is over.
Women too may find the anti-androgenic properties useful. When using steroids and virilizing symptoms start showing, using 50-75 mg of spironolactone can lessen the effect and allow a female to finish her cycle. And its especially useful for those gung ho women who use long acting androgens against better judgment, as even simply discontinuing the product will not stop side-effects. So spironolactone may come in handy.
Needless to say, spironolactone does not provide us with a get-out-of-jail-free card against androgenic side-effects. As long as you are making gains on any type of androgen, the risk for these side-effects remains nonetheless. But it can help us control them post-cycle. Also take care to note that aldosterone inhibitors and other types of diuretics have their own set of side-effects. Most notably cramping. Sodium and potassium, the two electrolytes most affected by diuretics, are essential to muscle contraction because without them, no proper action potential is formed in the neural cells that activate the muscle. As a result severe cramping can occur, sometimes to a point where training becomes near impossible. Diarrhea, dehydration, anxiety and weakness are also frequently associated with the use of diuretics.
For contest preparation purposes, a competitor would use 75-150 mg of aldactone per day for the 5-10 days leading up to a competition. A single early morning dose would suffice in this instance. The higher the dose, the greater the effect (though still mild, as aldactone is a relatively mild diuretic) but also the greater the chance of muscle loss on your diet, because of the anti-androgenic properties. To use it as a post-cycle recovery agent, 50-100 mg per day starting 1 to 1.5 weeks after your last shot of a long acting androgen, and running it until the end of post-cycle therapy (usually 4-5 weeks after) would provide you with the benefits of shedding water and promoting the return of natural testosterone alike.
The use of ancillaries is relatively useless here, because it acts as an anti-androgen, counters bloating and water retention and is used as an anti-hypertensive. So the common steroid side-effects are of no concern with the use of spironolactone.