Drug safety of Finasteride and Dutasteride

The drugs finasteride and dutasteride are drugs used in the treatment of different forms of alopecia in both men and women. They are drugs with great effectiveness and an excellent safety profile, with a very low risk of adverse effects. However, there is an unwarranted belief that these medications are unsafe.

Mechanism of action

The drugs finasteride and dutasteride are selective follicle root antiandrogens, that is, they exert their action directly on the hair root, without affecting other organs. They inhibit an enzyme called 5-alpha reductase (structure only present in the follicular root and in the prostate), inhibiting the action of male hormones (androgens) on the follicular root. Dutasteride inhibits this structure in a more powerful and lasting way, hence its greater effectiveness.

Both drugs began to be used and were launched on the market more than 20 years ago for the indication of benign prostatic hyperplasia in elderly men, in which an important improvement in capillary density was observed, and as a result, the pertinent studies of effectiveness and safety in alopecia in men and women. Many of the false myths about these drugs stem from misinterpretations of the package leaflet for these drugs when used at higher doses and in older males.

Possible Adverse Effects

Any medication can have adverse effects. However, finasteride and dutasteride have a very low risk of side effects (less than 3%), and in studies of thousands of patients they have seen that this risk is very similar to that of the general population who do not take medication (see reference 1).

One of the adverse effects classically seen in elderly males taking these medications was decreased libido or transient erectile dysfunction. Keep in mind that the doses they need are higher and that their older age predisposes them to problems of a sexual nature. However, these drugs rarely produce this effect at the doses used in alopecia, and even more so considering that patients receiving the drug are usually younger than men with prostate problems.

The side effects that could be observed in less than 3% of patients, and that in any case would be transitory, are: decreased libido, erectile dysfunction or increased breast volume.

Questions and Answers about Medical treatment with finasteride and dutasteride

1.- If a man takes finasteride or dutasteride for his alopecia, what effect does it have on his prostate?

At the doses commonly used in alopecia it would have no effect on the prostate. In any case, the effect would be positive, since it would prevent the prostate from growing abnormally.


2.- Can women take this medicine despite the fact that the package insert indicates that it is for men?

They can take it, always under medical indication. The use of a medicine outside the indication for which it was launched can be carried out, provided there is scientific evidence of its effectiveness and safety. In the case of finasteride and dutasteride, there are multiple studies supporting its effectiveness and safety in male and female alopecia (see references).


3.- What care should a woman taking finasteride or dutasteride take?

The most important: you should avoid becoming pregnant while taking the drug and for a time after stopping it (1 month in the case of finasteride and 6 months in the case of dutasteride). Having taken these drugs, however, does not have a negative impact on the future pregnancy of the patient.


4.- Do these drugs increase the risk of cancer?

These drugs do not increase the risk of any type of cancer. Important studies have been published demonstrating this fact (references 9 and 10).


5.- Is it necessary to carry out analytical controls or avoid any type of medication while taking these drugs?

As they are selective drugs on the follicular root, they are very safe drugs and usually do not require any analytical control or interact with other drugs. Follow the directions your doctor has given you about it.


6- Are these drugs financed by Social Security?

No. They are only funded for prostate hyperplasia in elderly males.


In the field of pharmacotherapy for different forms of alopecia, we can say that finasteride and dutasteride are very effective and safe medications for men and women with both androgenic  and other types of alopecia.

Clinical experience and scientific evidence support the safety of these medications. Although no drug is exempt from producing any adverse effects, the strongest studies on the safety of finasteride and dutasteride show that the risk of adverse effects taking these drugs is practically the same as patients who do not take them.

These drugs can also be used under medical prescription in women (off-label use), taking care to avoid pregnancy during treatment and after a time (1 month for finasteride and 6 months for dutasteride).

1-Effect of 5α-Reductase Inhibitors on Sexual Function: A Meta-Analysis and Systematic Review of Randomized Controlled Trials. Lui L, Zhao S, Li F et al. J Sex Med. 2016 Sep;13(9):1297-1310.


2-New Treatments for Hair Loss. Vañó-Galván S, Camacho F. Actas Dermosifiliogr. 2017 Apr;108(3):221-228. doi: 10.1016/j.ad.2016.11.010.


3-Superiority of dutasteride over finasteride in hair regrowth and reversal of miniaturization in men with androgenetic alopecia: A randomized controlled open-label, evaluator-blinded study.

 Shanshanwal SJ, Dhurat RS. Indian J Dermatol Venereol Leprol. 2017 Jan-Feb;83(1):47-54


4-Safety and Tolerability of the Dual 5-Alpha Reductase Inhibitor Dutasteride in the Treatment of Androgenetic Alopecia. Choi GS, Kim JH, Oh SY, Park JM, Hong JS, Lee YS, Lee WS. Ann Dermatol. 2016 Aug;28(4):444-50.


5-The effectiveness of finasteride and dutasteride used for 3 years in women with androgenetic alopecia. Boersma IH, Oranje AP, Grimalt R, Iorizzo M, Piraccini BM, Verdonschot EH. Indian J Dermatol Venereol Leprol. 2014 Nov-Dec;80(6):521-5


6-Long-term safety and efficacy of dutasteride in the treatment of male patients with androgenetic alopecia. Tsunemi Y, Irisawa R, Yoshiie H, Brotherton B, Ito H, Tsuboi R, Kawashima M, Manyak M; ARI114264 Study Group. J Dermatol. 2016 Sep;43(9):1051-8.


7-A randomized, active- and placebo-controlled study of the efficacy and safety of different doses of dutasteride versus placebo and finasteride in the treatment of male subjects with androgenetic alopecia. Gubelin Harcha W, Barboza Martínez J, Tsai TF, Katsuoka K, Kawashima M, Tsuboi R, Barnes A, Ferron-Brady G, Chetty D. J Am Acad Dermatol. 2014 Mar;70(3):489-498.e3.


8-Finasteride 5 mg/day Treatment of Patterned Hair Loss in Normo-androgenetic Postmenopausal Women. Oliveira-Soares R, E Silva JM, Correia MP, André MC. Int J Trichology. 2013 Jan;5(1):22-5


9-Finasteride concentrations and prostate cancer risk: results from the Prostate Cancer Prevention Trial. Chau CH, Price DK, Till C, et al. PLoS One. 2015 May 8;10(5):e0126672.


10-Long-term use of 5α-reductase inhibitors and the risk of male breast cancer. Duijnhoven RG, Straus Sm Souverein PC, et al. Cancer Causes Control. 2014 Nov;25(11):1577-82.

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