Adverse events affecting reproductive anatomy & sexual function in men ages 18–40

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.

Category	Adverse events (2000–2020)
Erectile dysfunction & sexual dysfunction	1,021
Penile abnormalities	494
Testicular abnormalities	301
Semen and sperm abnormalities	259
Ejaculatory dysfunction	166
Prostatic adverse events	69
Total	2,310

There were a total of 13,592 AEs in this data set. This subset represents 17% of the total.

Adverse events by category

Erectile dysfunction & sexual dysfunction

Adverse Event	Count
Erectile Dysfunction; Organic Erectile Dysfunction; Sexual Dysfunction; Male Sexual Dysfunction	1,021

Penile abnormalities

Adverse Event	Count
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
Total	494

* This AE is broader in scope and ambiguous; it could have been classified in other categories.
** Other genital abnormalities: Genital Cyst; Male Genital Examination Abnormal; Urogenital Disorder; Genital Tract Inflammation

Testicular abnormalities

Adverse event	Count
Testicular Pain	174
Testicular Atrophy	67
Testicular Disorder; Testicular Failure	47
Other Testicular Abnormalities ^§	13
Total	301

^§ Other Testicular abnormalities: Microlithiasis; Testicular Torsion, Testicular Mass, Testicular Germ Cell Tumour, Seminoma

Semen & sperm abnormalities

Adverse event	Count
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
Total	259

Ejaculatory dysfunction

Adverse event	Count
Ejaculation Disorder	90
Ejaculation Failure; Retrograde Ejaculation; Painful Ejaculation	61
Premature Ejaculation	15
Total	166

Prostatic adverse events

Adverse event	Count
Prostatitis	25
Prostatic Pain	22
Prostatic Disorder	10
Benign Prostatic Hyperplasia; Prostatomegaly	5
[Other prostatic AEs] Prostate Tenderness; Carcinoid Tumour; Bacterial Prostatitis, Prostate Calcification	7
Total	69

Methodology

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.

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.

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).