This post documents adverse events (AEs) of finasteride affecting male reproductive anatomy and sexual function in men age 18–40, reported to US FDA from 2000 to 2020. See the Methodology section for more details.
Categories in the table are not in the source data, but were applied based on AE descriptions:
|Erectile dysfunction & sexual dysfunction||1,021|
|Semen and sperm abnormalities||259|
|Prostatic adverse events||69|
There were a total of 13,592 AEs in this data set. This subset represents 17% of the total.
Prevalence of these (or any) AEs among all men 18-40 who took finasteride cannot be estimated based on this data. AEs are likely underreported, but the extent of underreporting is unknown.
Adverse events by category
Erectile dysfunction & sexual dysfunction
Erectile dysfunction is frequently interpreted as a psychogenic phenomenon. A future post will propose that persistent sexual dysfunction linked to finasteride treatment emerges from damage to penile vascular tissue and nerves, and therefore is not primarily psychogenic. Nevertheless, these reports of sexual dysfunction (excepting “Organic Erectile Dysfunction”) do not specify whether the AE is of psychogenic origin.
|Erectile Dysfunction; Organic Erectile Dysfunction; Sexual Dysfunction; Male Sexual Dysfunction||1,021|
|Penile Size Reduced; Penis Disorder; Peyronie’s Disease; Male Genital Atrophy; Genital Disorder; Penile Curvature; Genital Atrophy||277|
|Genital Hypoaesthesia [numbness]||92|
|Penile Pain; Genital Pain; Burning Sensation; Genital Discomfort; Paresthesia; Painful Erection||80|
|Male Reproductive Tract Disorder *||24|
|Penile Vascular Disorder; Haemorrhage||12|
|Other Genital Abnormalities **||9|
** Other genital abnormalities: Genital Cyst; Male Genital Examination Abnormal; Urogenital Disorder; Genital Tract Inflammation
|Testicular Disorder; Testicular Failure||47|
|Other Testicular Abnormalities §||13|
Semen & sperm abnormalities
|Semen Volume Decreased||82|
|[Sperm concentration] Sperm Concentration Decreased; Azoospermia; Oligospermia; Sperm Concentration Zero; Hypospermia; Sperm Concentration Abnormal||54|
|[Semen consistency] Semen Viscosity Decreased; Semen Viscosity Increased; Semen Viscosity Abnormal; Semen Liquefaction Abnormal; Semen Liquefaction||40|
|Semen Analysis Abnormal||32|
|[Sperm morphology] Spermatozoa Abnormal; Spermatozoa Progressive Motility Decreased; Spermatozoa Morphology Abnormal; Teratospermia; Spermatogenesis Abnormal||23|
|Semen Discolouration; Haematospermia||19|
|[Sperm motility (movement)] Asthenospermia; Spermatozoa Progressive Motility Abnormal||5|
|[Other abnormalities] Sperm Analysis Abnormal; Semen Volume Increased; Oligoasthenozoospermia||4|
|Ejaculation Failure; Retrograde Ejaculation; Painful Ejaculation||61|
Prostatic adverse events
|Benign Prostatic Hyperplasia; Prostatomegaly||5|
|[Other prostatic AEs] Prostate Tenderness; Carcinoid Tumour; Bacterial Prostatitis, Prostate Calcification||7|
This post documents adverse events (AEs) of finasteride affecting male reproductive anatomy and sexual function, reported to the US FDA Federal Adverse Event Reporting System (FAERS) and downloaded from the FAERS Public Dashboard.
Data were limited to reports for men ages 18 to 40 who used finasteride, which were received by FDA between January 1, 2000 and December 31, 2020. Some cases include other drugs and products used concomitantly. To limit the influence of the submitter’s judgment, the analysis did not filter on the ‘Suspect Product’ field. Cases were not filtered by the ‘Reason for Use’ field.
Most reports of erectile dysfunction and sexual dysfunction did not specify whether the origin was psychogenic or organic (the exception is the AE ‘Organic Sexual Dysfunction’).
AEs were grouped post hoc into the categories shown in the first table. Subsequent tables list AE terms within each category. Within a category, similar AEs were grouped and appear in separate rows, with individual AE terms delimited by semicolons.
Signal analysis not performed
A methodology of pharmacovigilance called signal analysis compares AEs across drugs to determine whether one drug has a unique signal compared to a larger universe. A signal analysis has not been performed on these data. At the same time, various forms of evidence have linked finasteride to the following symptoms or effects:
- Erectile dysfunction: strong evidence from clinical trials and post-marketing reports;
- Penile tissue alterations: strong evidence from animal studies (see bibliography) and emerging evidence from human studies (Khera et al. and Schifano et al. in bibliography);
- Testicular abnormalities: a few animal studies in this bibliography have linked finasteride to testicular abnormalities. Testicular pain is included in the post-marketing experience section of the Propecia label (although inclusion of such events is partly informed by adverse event reports in the first place);
- Semen abnormalities: the Propecia label includes the adverse reaction “male infertility and/or poor seminal quality” in the post-marketing experience section. Animal and human studies have shown that finasteride can have adverse effects on semen and sperm parameters. Amory et al 2007 reported that two men who took finasteride (5 mg/day) and one who took dutasteride (0.5 mg/day) had sperm counts decline to less than 10% of baseline during the trial; and six months after discontinuing the treatment, their sperm counts remained below 33% of baseline.
- Effects on prostate tissue: strong evidence from clinical trials for finasteride (5 mg/day) and clinical experience indicate that finasteride can reduce the size and weight of the prostate. There has been debate about the evidence for increased risk of high-grade prostate cancer linked to finasteride use (see Liss & Thompson 2018 and Wang et al 2020).
1. Schifano N, et al. Is finasteride intake associated with penile curvature/Peyronie’s Disease? 2021. doi:10.1016/S2666-1683(21)00727-8
2. Review: Alterations to penile and prostatic tissue associated with finasteride and dutasteride treatment
3. Bibliography on penile and prostatic alterations linked to finasteride treatment
4. Summary of top 25 adverse events of finasteride taken by younger men for hair loss.