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Finasteride (Propecia) is sold under the trademarks Proscar and Propecia, the drug is used to treat benign prostatic hyperplasia (enlarged prostate) and hair loss. It is an inhibitor of 5α-reductase type II and type III; 5α-reductase, an enzyme that converts testosterone to dihydrotestosterone (DHT).

Mechanism of action

Propecia is an inhibitor of 5α-reductase, in particular, type II and III isoenzymes. When inhibiting 5-reductase, finasteride prevents the conversion of testosterone to dihydrotestosterone (DHT), to type II and III isoenzymes lead to a decrease in the serum DHT level by approximately 65-70%, and in the prostate the level of DHT to 85-90%, where the predominant manifestation in II type of isoenzyme. Unlike the triple inhibitors of all three 5a-reductase isoenzymes such as dutasteride, can reduce the level of DHT throughout the body by more than 99%, finasteride does not completely suppress the production of DHT, since it does not have a significant inhibitory effect on the type of 5α-reductase I of the isoenzyme , is 100 times less affinity in I than in II.

By blocking the production of DHT, Propecia reduces the activity of androgens in the scalp. In the prostate gland, inhibition of 5a-reductase reduces the volume of the prostate gland, benign prostatic hyperplasia, which improves and reduces the risk of developing prostate cancer. Inhibition of 5-reductase also reduces the weight of the epididymis, and reduces the mobility and normal morphology of spermatozoa in the epididymis. Neurosteroids like 3 alpha androstanediol and allopregnanolol activate the GABA receptor; because Finasteride interferes with the formation of neurosteroids, it can help reduce the activity of GABA. Reduced activation of the GABA receptor by these neurosteroids contributed to the manifestation of depression, anxiety and sexual dysfunction.

In addition to the inhibition of 5-alpha-reductase, a competitor, a 5 beta reductase inhibitor, was also found in finasteride, although its affinity for the enzyme is significantly less than in the 5 reductase (an order of magnitude smaller than in the 5α-reductase I type) there is unlikely to be clinical significance.

Medical applications of Finasteride (Propecia)

Enlarged prostate

Doctors use Propecia to treat BPH, informally known as prostate enlargement. Propecia can improve the symptoms associated with prostatic adenoma, such as difficulty urinating, getting up at night for urination, questioning the beginning of urination and reducing the flow of urine. This provides less symptomatic treatment than alpha-1 blockers such as tamsulosin and symptom relief occurs more slowly at the beginning (for treatment with finasteride it may take six months or more to determine the therapeutic outcome of the treatment).

Symptomatic advantage is mainly seen in people with a prostate> 40 cm3. In long-term studies, finasteride, but not alpha-1 inhibitors, reduce the risk of acute urinary retention (-57% at 4 years) and the need for surgery (-54% at 4 years). When you stop taking the drug, the changes in the prostate gland are restored within 6-8 months.


Finasteride is used to treat hair loss (androgenic alopecia) only in men. The treatment slows down further hair loss and provides about 30% improvement from hair loss after six months of treatment, the effectiveness is maintained only as long as the drug is taken. Finasteride has also been tested for hair loss in women; but the results were no better than placebo.

Side effects of Propecia

Side effects from Propecia are rare. Compared to placebo, men taking finasteride are at increased risk of impotence, erectile dysfunction, decreased libido, and ejaculatory abnormalities during the first year of treatment. The rate of these effects becomes indistinguishable from placebo in 2-4 years, and these side effects usually weaken over time. The FDA added a 5-alpha reductase warning regarding the increased risk of developing high-grade prostate cancer, as treatment with BPH reduces the level of PSA (prostate-specific antigen) that could mask the development of prostate cancer. Although the overall incidence of breast cancer in men in clinical trials for finasteride has not been increased – 5 mg, there is a post-marketing report on breast cancer due to its use. The available data do not provide clarity as to whether there is a causal relationship between finasteride and these cancers. finasteride side effects

In 2015, a meta-analysis revealed that none of the clinical trials of finasteride testing in hair loss provide adequate reporting, security and no sufficient information to establish a safety profile for finasteride as a treatment for hair loss. The study concluded that the existing clinical trials of finasteride against hair loss give very limited information on toxicity, poor quality, and systematically presented bias toward side effects. In addition, during trials submitted to the FDA, the approval of hair loss excluded most men who, as a rule, prescribed finasteride for androgenic alopecia.

Propecia in bodybuilding

Many sports organizations have banned Propecia, because the drug can be used to mask the use of steroids. Since 2005, Finasteride is on the list of substances banned by the World Anti-Doping Agency. However, in 2009 the drug was removed from this list. A number of famous athletes who used Finasteride as a means of hair loss and excluded from international competitions are headed by skeletonist Zak Lund, bobsledder Sebastian Gattuso, footballer Romario and goalkeeper in ice hockey Jose Theodore. finasteride results

Forms of release

Trade names include Propecia and Proscar, which, firstly, are used to treat male pattern baldness, and, secondly, for the treatment of benign prostatic hyperplasia (BPH), and both are products of Merck & Co. Propecia contains 1 mg Finasteride, and Proskar contains 5 mg. The Merck patent for Finasteride for the treatment of BPH expired on June 19, 2006. Merck received a separate patent for the use of Finasteride for the treatment of male pattern baldness. This patent expires in November 2013. Studies have shown that the dose of Finasteride needed to treat male pattern baldness is less than 1 mg. The FDA filed petitions regarding the revision of approved dosages in the light of statistical data and the availability of possible long-term risks. However, the FDA stated that there are results of the study, where a dose increase of 1 mg compared to 0.2 mg showed an increase in the effect without additional risks. The same study also concluded that doses of 0.01 mg per day were ineffective in the treatment of alopecia. Finasteride is a lipophilic substance. Recently, the development of the liposome system of Finasteride for topical application has begun. Formulas for topical application may have some effect on the reversal of androgenic effects on hair follicles, as well as on hirsutism. In later studies, microemulsions and liquid crystal nanoparticles of Finasteride were considered for topical application. In the latter case, the addition of glycerol, propylene glycol and polyethylene glycol 400 increased the penetration of Finasteride, while the addition of oleic acid caused a decrease in this penetration. Finasteride for topical administration in combination with minoxidil is more effective than minoxidil alone. In small studies, finasteride for topical application in combination with other drugs has also been found to be effective. Surface-active substances can promote local penetration of the drug. Finasteride also proved to be effective in the form of a gel for topical application.

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