Finasteride and Dutasteride, their safety

Two of the most commonly used drugs by trichologists for the treatment of different types of alopecia are Finasteride and Dutasteride. Despite having a very high safety profile, these medications often raise concerns among patients. These concerns are completely unfounded and influenced by package inserts and popular opinion.

Adverse effects listed for these medications are related to male sexuality, as they include a potential decrease in erectile function, libido, and/or ejaculatory volume. However, these effects occur in very rare cases, barely 3%, and typically reverse with dose adjustment or discontinuation of treatment.

In any case, understanding these adverse effects requires knowledge of the mechanism of action of the medications, as well as their dosage and administration.

Functioning of Finasteride and Dutasteride

Both Finasteride and Dutasteride act as inhibitors of 5-alpha reductase, an enzyme present in the root of hair follicles (and in the prostate). They are highly selective medications that only work on these follicles, without affecting any other organs. Dutasteride acts more intensely on this enzyme and is able to remain in the body for a longer period.

As we mentioned, both medications were initially approved for the treatment of benign prostatic hyperplasia and launched on the market in the 1990s. They were indicated for elderly men, and improvement in hair density was observed during treatment, prompting studies to ensure effectiveness in treating alopecia in both men and women.

Adverse Effects, the Major Concern

Adverse effects are common in all medications. That’s why they are listed in their own section within the leaflets of the medications we take throughout our lives. However, just because they are written down doesn’t mean we will definitely experience them. In fact, they are uncommon and reversible after adjusting the doses or discontinuing the medication.

Regarding Finasteride and Dutasteride, they are both completely safe medications. Adverse or side effects occur in only 3% of the population. These risks are very similar compared to the population that does not regularly take these drugs.

The major concern of the population taking these medications regularly is a decrease in libido or transient erectile dysfunction. However, these symptoms typically occur in older patients with diagnosed prostate problems. Due to age, they are also more prone to such disorders. In younger patients, however, these symptoms are very rarely developed.


¿What should I consider when taking Finasteride or Dutasteride?

You should consider that these medications should be prescribed and regulated only by specialist doctors, such as Dr. Espinosa Custodio. It will be the doctors who ensure a fair dosage for our safety. Both men and women can take them indiscriminately, although it is necessary to inform about pregnancy attempts. These medications can affect the proper development of the fetus by reducing the quality of semen or eggs.

¿Will this medication affect the prostate?

In the doses commonly used for hair treatments, it will not affect the prostate. If it were to do so, it would be in a positive way, helping to prevent problems.

Dr. Espinosa Custodio works at the Instituto Médico del Prado, his hair clinic in Madrid or in Mexico City. If you wish to schedule an appointment, you can contact us at the phone number +34 912 468 664, on WhatsApp +34 627 396 322, or through the contact page on our website. If you are contacting us from Mexico, our phone number is +52 55 4590 9909.


The effect of finasteride on the risk of acute urinary retention and the need for surgical treatment among men with benign prostatic hyperplasia. Finasteride Long-Term Efficacy and Safety Study Group. N Engl J Med., 338 (1998), pp. 557-563 J.D. McConnell, R. Bruskewitz, P. Walsh, et al. | Medline

Efficacy and safety of finasteride therapy for benign prostatic hyperplasia: Results of a 2-year randomized controlled trial (the PROSPECT study). PROscar Safety Plus Efficacy Canadian Two year Study. CMAJ., 155 (1996), pp. 1251-1259J.C. Nickel, Y. Fradet, R.C. Boake, et al. Medline

Incidence and severity of sexual adverse experiences in finasteride and placebo-treated men with benign prostatic hyperplasia. Urology., 61 (2003), pp. 579-584. H. Wessells, J. Roy, J. Bannow, et al. Medline.

Benign prostatic hyperplasia. Lancet., 361 (2003), pp. 1359-1367. A. Thorpe, D. Neal. Recuperado de: | Medline

A review of the clinical efficacy and safety of 50alpha-reductase Inhibitors for the enlarged prostate. Clin Ther., 29 (2007), pp. 17-25. M. Naslund, M. Miner. | Medline

Effect of 5α-reductase inhibitors on sexual function: A meta-analysis and systematic review of randomized controlled trials. J Sex Med., 13 (2016), pp. 1297-1310L. Liu, S. Zhao, F. Li, et al. | Medline

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