Spironolactone

At Spironolactone it is a so-called competitive antagonist to the receptor for mineralocorticoids. The active ingredient spironolactone belongs to the pharmacological group of diuretics, which have potassium-sparing properties. The drug is on the WHO list as an indispensable drug.

What is spironolactone?

Spironolactone is a pharmacological agent that is used as a drug for the treatment of various complaints and diseases. It causes more water to be washed out of the body.

By taking it, the effect of the steroid homone aldosterone is reduced, which is why the excretion of sodium is reduced. Because of this, it is possible that a higher proportion of potassium will be retained. Because the aldosterone hampers or makes it completely impossible to incorporate into the sodium channel. As a result of this mechanism, there is an increased excretion of water.

Pharmacological effect

The mechanism of action of spironolactone is primarily based on the fact that the substance blocks the aldosterone receptors. As a result, more water and sodium are excreted. At the same time, a greater amount of potassium is retained.

If the drug spironolactone is taken orally, the bioavailability is over 90 percent. First, the substance is absorbed in the small intestine. The drug is then metabolized into the active ingredient canrenoate. In the majority of cases, the half-life of the active ingredient is around 90 minutes.

Basically, however, the full effect of the spironolactone only shows after a few days. Because it is necessary that the active metabolites accumulate in sufficient quantities. The greatest possible diuretic effect of the drug is achieved in most cases after about five days. It should be noted that the onset of the effect of spironolactone cannot be brought about more quickly by increasing the dose.

Spironolactone blocks the collecting tubes in the kidneys. The substance aldosterone is no longer able to bind to its receptor. The sodium channels are hindered during their installation, while at the same time the luminal membrane on the main cells is blocked. This severely affects the reabsorption of sodium. As a result, water does not move into the so-called collecting pipes of the kidneys. This means that no more water gets into the blood.

Instead, there is an increased excretion of sodium and water. Therefore the amount of blood in the organism also decreases. Thus the heart is relieved, which is why the blood pressure decreases. In addition, accumulations of water in the tissue are washed out.

The loss of potassium, which is a consequence of numerous diuretics, is compensated by a combined therapy with spironolactone. Clinical studies have shown that treatment with the active ingredient spironolactone has a positive effect on the prognosis and chances of survival in chronic heart failure.

The resorption of the substance spironolactone usually proceeds well following oral administration. After one hour, the active ingredient in the plasma is completely eliminated. However, various metabolic products remain. Basically, these metabolites are largely responsible for the drug's effect.

In principle, the metabolism of the drug is complex. The substance canrenon plays an important role in this and shows up in both urine and blood. Numerous metabolic products from this process are excreted in the stool and bile.

Medical application & use

The drug spironolactone is mostly used to treat cirrhosis of the liver and heart failure. Depending on the individual indication, the attending physician prescribes dosages of 25 to 100 milligrams per day.

In addition, the drug spironolactone is also used at elevated concentrations of aldosterone. The underlying diseases are mostly liver cirrhosis or primary hyperaldosteronism.

Spironolactone is very effective for chronic heart failure. However, it tends to be rarely used for this purpose in Europe, while it is used as a standard drug in the US.

Spironolactone is also used in endocrinology in people with transsexuals. The drug acts as a testosterone blocker by hindering the synthesis of the hormone and its binding to the corresponding androgen receptors.

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Risks & side effects

As part of therapy with the drug, various undesirable side effects and complaints are possible, which differ depending on the patient and the individual case. Most commonly, there is an increased level of potassium in the blood. For this reason, the patient should be monitored by a doctor while taking it.

With high doses of the drug, hormonal disorders are also possible. These are expressed, for example, in the fact that women do not have a menstrual period. Male patients may have erectile dysfunction or voice changes. In transsexual people, exactly these effects are sometimes desired.

Interactions can be seen, for example, when the active ingredient digoxin is taken at the same time. Increased concentrations of cardiac glycoside in the plasma are possible. Other side effects can include hyperkalemia, gynecomastia, or impotence.

Some of the side effects of spironolactone lead the drug to be used as a doping agent in sports. It should be noted that misuse of the active ingredient and an overdose significantly increases the risk of damage to the kidneys.