How finasteride works
Finasteride is a drug from the class of 5-alpha-reductase inhibitors. 5-alpha-reductase is an enzyme responsible for converting testosterone into the active form 5-alpha-dihydrotestosterone (DHT).
The hormone testosterone is primarily responsible for the formation of male sexual characteristics and is found everywhere in the human body. When testosterone is converted by 5-alpha-reductase, DHT is formed, which binds very specifically to certain docking sites.
A signal is then transmitted which, in sensitive men, can lead to tissue proliferation of the prostate gland and hair loss, among other things.
In most older men, the prostate is benignly enlarged. Due to the pressure of the newly formed tissue on the urethra, in many cases there is discomfort during urination, frequent urge to urinate at night, problems with complete emptying of the bladder, and even backflow damage with urinary tract disease and kidney dysfunction.
Finasteride inhibits the enzyme 5-alpha-reductase. As a result, the concentration of dihydrotestosterone decreases. As a result, the size of the prostate decreases and hormonally induced hair loss is stopped.
Absorption, degradation and excretion
When is finasteride used?
Fields of application (indications) of finasteride are dose-dependent:
- Benign tissue proliferation of the prostate gland (benign prostatic hyperplasia)
- Androgenetic alopecia (hormonally induced hair loss)
How finasteride is used
The most commonly used dosage form is the film-coated tablet. The active ingredient is located in the core of the tablet and is surrounded by a protective coating. This prevents the active ingredient from being absorbed through the skin when the tablet is touched.
The dosage for men with benign prostate enlargement is five milligrams per day. For treatment of hormonally induced hair loss, only one milligram is taken daily. Patients suffering from liver dysfunction are given a reduced dose.
The tablet is taken independently of a meal with sufficient liquid (preferably a large glass of tap water).
In benign prostate enlargement, finasteride is often administered in combination with a so-called “alpha-1-adrenoceptor blocker” (such as tamsulosin). Due to the different mechanisms of action, a very effective control of symptoms and causes at the same time is possible.
What are the side effects of finasteride?
Often (that is, in one to ten percent of those treated) finasteride causes side effects such as decreased libido and sexual dysfunction.
Rarely (that is, in less than one percent of those treated), feelings of tightness in the breast occur. Even more rarely, use causes lumps in the breast or fluid discharge from the mammary gland.
In fetuses, finasteride leads to malformations of the external sexual characteristics. Therefore, pregnant women and women who may become pregnant should not come into contact with the drug.
What should be considered when taking finasteride?
Contraindications
Pregnant women and women who may become pregnant should not take medications containing finasteride and should not divide or crush the tablets.
Drug interactions
So far no clinically relevant interactions with other medications are known.
Warnings and precautions
Finasteride may alter a certain laboratory value (PSA; prostate specific antigen) used for identification and early detection of a malignant change in prostate tissue (tumor). The possibility of a tumor must therefore be ruled out by the treating physician before therapy.
If nodular changes, pain, or secretions from the mammary gland occur while taking finasteride, seek immediate medical attention.
Age restriction
Finasteride is contraindicated in children and adolescents under 18 years of age.
Pregnancy and breastfeeding
Finasteride is not intended for use in women.
Men taking finasteride should take care when having sex with pregnant women that the woman does not come into contact with the semen (for example, by using a condom).
The reason: finasteride can also be detected in semen. If the active substance reaches the unborn child, this can lead to malformations of the external sexual characteristics.
How to obtain medication with finasteride
Finasteride requires a prescription in Germany, Austria and Switzerland and is therefore only available from pharmacies with a prescription from a doctor.
Other interesting facts about Finasteride
Until recently, the active ingredient Finasteride was known as a doping agent. The aim of athletes was to mask the use of the banned doping agent testosterone (leads to increased muscle growth and general performance enhancement).
In the meantime, however, doping tests have become so sensitive that unnaturally elevated levels of testosterone can be detected despite taking finasteride. Finasteride has thus lost its significance as a doping agent today.
