The table below shows the top 25 adverse events reported to the U.S. Food & Drug Administration (FDA) concerning finasteride used by younger men as a treatment for hair loss, from 2019–2021. The following filters were applied to minimize confounding factors:
Date first received by FDA: 2019–2021 / Sex: Male / Age: 18-40 / Suspected product: Finasteride only / Reason for use: Hair loss conditions only, excluding hair transplant / Concomitant products: None. Selected cases: 499 (17.5% of all finasteride-related cases during this time period). Median age: 28y. Submitted by: Consumer, 74.7%; Healthcare provider, 25.1%; Not specified: 0.2%.
| Category of adverse events | % of top 25 adverse events |
| Sexual anatomy & function Erectile Dysfunction / Organic Erectile Dysfunction – 249 Loss Of Libido / Libido Decreased – 206 Testicular Pain – 61 Sexual Dysfunction – 45 Genital Hypoaesthesia [numbness] – 34 Ejaculation Disorder – 33 Penile Size Reduced – 30 | 40% |
| Neuropsychiatric domain Depression / Depressed Mood – 188 Anxiety – 125 Suicidal Ideation – 103 Feeling Abnormal – 70 Anhedonia [inability to feel pleasure] – 39 Panic Attack – 38 | 34% |
| Cognition, memory & attention Cognitive Disorder – 54 Amnesia – 38 Disturbance In Attention – 34 | 8% |
| Energy Fatigue / Asthenia – 114 | 7% |
| Sleep Insomnia / Sleep Disorder – 108 | 6% |
| Multi-system Post 5-Alpha Reductase Inhibitor Syndrome – 57 | 3% |
| Sensory Tinnitus – 38 | 2% |
Explore and download the data (Airtable) ↗
Because 75% of these reports were submitted by Consumers, a separate analysis was done on reports submitted by healthcare providers. The composition of categories was similar, but there was a higher proportion of AEs in the neuropsychiatric category and a lower proportion in sexual anatomy & function:
| Category | % of top 25 adverse events |
|---|---|
| Neuropsychiatric domain | 41% |
| Sexual anatomy & function | 27% |
| Multi-system* | 8% |
| Sleep | 8% |
| Cognition, memory & attention | 5% |
| Energy (Fatigue) | 5% |
| Other (Dizziness & Headache) | 4% |
| Endocrine (Gynaecomastia) | 2% |
See also: Adverse events affecting reproductive anatomy and sexual function, musculoskeletal adverse events, disability and deaths, and firsthand reports acquired by FOIA request.
Comparison to adverse events of minoxidil
Minoxidil is another treatment for hair loss used by younger men. It has a similar patient population as finasteride, but a different mechanism. A comparison of adverse events (AEs) of each drug can shed light on whether AEs might be attributable to the population or the drug.
Data for both drugs were filtered using the same criteria: Date first received by FDA: 2019–2021 / Sex: Male / Age: 18-40 / Suspected product: Minoxidil only or Finasteride only / Reason for use: hair loss conditions, excluding hair transplant / Concomitant products: None. Number of cases: Finasteride, 499; Minoxidil, 360.
Minoxidil AEs by category
| Category | % of top 25 AEs |
| Skin reactions | 45% |
| Incorrect use of product | 29% |
| Hair loss & drug ineffective | 14% |
| Headache & dizziness | 7% |
| Sexual dysfunction | 4% |
Finasteride AEs by category
| Category | % of top 25 AEs |
| Sexual anatomy & function | 40% |
| Neuropsychiatric domain | 34% |
| Cognition, memory & attention | 8% |
| Energy | 7% |
| Sleep | 6% |
| Multi-system* | 3% |
| Sensory | 2% |
Comparison
The only AE common to both drugs’ top 25 is Sexual Dysfunction:
| Finasteride | Minoxidil | |
| Adverse event: Sexual Dysfunction | 2.7% | 2.6% |
| Category: Sexual anatomy & function | 40.0% | 4.4% |
Treemaps
These figures show the category composition of the top 25 AEs of each drug.
Detailed data: Top 25 AEs of minoxidil and finasteride grouped by category
| Minoxidil | Finasteride |
| Skin reactions Application Site Pruritus – 63 Application Site Pain – 29 Application Site Erythema – 27 Application Site Rash – 21 Application Site Dryness – 19 Pruritus – 16 Rash – 15 Application Site Exfoliation – 15 Application Site Irritation – 15 Dandruff – 12 Swelling Face – 11 Application Site Swelling – 11 Application Site Ulcer – 11 Incorrect use of product Inappropriate Schedule Of Product Administration – 58 Incorrect Dose Administered – 26 Underdose – 25 Product Use In Unapproved Indication – 22 Overdose – 22 Product Administered At Inappropriate Site – 18 Hair loss & drug effectiveness Alopecia – 57 Drug Ineffective – 25 Headache & dizziness Headache – 24 Dizziness – 17 Sexual function Erectile Dysfunction – 15 Loss Of Libido – 11 | Sexual anatomy & function Erectile Dysfunction / Organic Erectile Dysfunction – 249 Loss Of Libido / Libido Decreased – 206 Testicular Pain – 61 Sexual Dysfunction – 45 Genital Hypoaesthesia [numbness] – 34 Ejaculation Disorder – 33 Penile Size Reduced – 30 Neuropsychiatric domain Depression / Depressed Mood – 188 Anxiety – 125 Suicidal Ideation – 103 Feeling Abnormal – 70 Anhedonia [inability to feel pleasure] – 39 Panic Attack – 38 Cognition, memory & attention Cognitive Disorder – 54 Amnesia – 38 Disturbance In Attention – 34 Energy Fatigue / Asthenia – 114 Sleep Insomnia / Sleep Disorder – 108 Multi-system Post 5-Alpha Reductase Inhibitor Syndrome – 57 Sensory Tinnitus – 38 |