Finasteride and Minoxidil Side Effects

Finasteride Side Effects

Erectile dysfunction occurs in an additional 2-4% of patients compared to placebo, with absolute rates ranging from 4.2% to 15.8% depending on study duration 1, 2, 3, 4, 5
Decreased libido affects 2-4% more patients than placebo, with rates of 3.4-10% in treatment groups 1, 2, 3, 4, 5
Reduced ejaculate volume is reported in 1.5-7.2% of patients, representing a 2.6-fold increased risk versus placebo 1, 2
The magnitude of sexual dysfunction is clinically modest: on a 0-100 scale, finasteride causes a mean difference of only 3.21 points compared to 1.26 points for each year of aging 3, 4, 5
Sexual side effects decrease over time and remain statistically significant but clinically small after the first year 3, 4, 5, 6, 7
Gynecomastia (breast enlargement) occurs in 0.5-2.2% of patients versus 0.1-1.1% with placebo 1, 2, 3, 4, 5
Breast tenderness affects 0.4-0.7% of patients 1, 2
The FDA amended finasteride labels to warn about persistent symptoms after discontinuation, though this is based on anecdotal patient reports rather than prospective trials 8, 9
Post-finasteride syndrome remains poorly defined and controversial, with unclear data quality supporting its existence 8, 9
Overall discontinuation rates are approximately 15% for both finasteride and placebo groups 1, 2, 3, 4, 5
Discontinuation specifically due to adverse events is 6-7% in both treatment and placebo groups 3, 4, 5

PSA levels must be doubled after 12 months of therapy to accurately interpret prostate cancer screening 3, 4, 5
Delayed cancer diagnosis may occur if PSA adjustment is not performed, potentially leading to worse outcomes 8, 9
Laboratory abnormalities are minimal: finasteride decreases PSA by 50% (requiring doubling of values for interpretation) but causes no other clinically significant changes 3, 4, 5

In mid-term studies (1-2 years), rates of erectile dysfunction range from 4.2% to 15.8% depending on the study population, as reported by the Journal of Clinical Oncology 10
The PCPT trial reported a 67.4% cumulative incidence of erectile dysfunction over 7 years versus 61.5% with placebo, though this includes baseline sexual dysfunction in an older population, as reported by the Journal of Clinical Oncology 10

Higher rates of erectile dysfunction are consistently reported in BPH populations, with most studies showing correlation between finasteride and ED, although the exact rates are not specified in the cited reference, as reported by the Journal of Clinical Oncology 10
The 1 mg dose of finasteride produces similar PSA suppression (50% decrease at 1 year) as the 5 mg dose in men over 50 years, as reported by the Journal of Clinical Oncology 10

Baseline sexual dysfunction is common in BPH populations, with 46% of men in the PLESS study having a history of sexual dysfunction at screening, as reported by The Journal of Urology 11
The PCPT study population (mean age 62-65 years) had high baseline rates of sexual dysfunction, as reported by The Journal of Urology 11 and the Journal of Clinical Oncology 10

The American Urological Association notes that finasteride and dutasteride have essentially equivalent effects on erectile function, with no clinically meaningful difference between the two medications 12

Erectile dysfunction occurs with a relative risk of 1.10 compared to placebo with finasteride, as shown in longer-term studies 13

The American Urological Association guidelines suggest choosing between finasteride and dutasteride based on factors other than erectile function impact, such as cost or efficacy considerations, as their effects on erections are equivalent 12

In randomized clinical trials, finasteride produced a mean reduction in sexual function of ≈ 3.2 points on a 0–100 scale, which is modest compared with the ≈ 1.3‑point decline per year of aging in untreated men【14】.
The absolute increase in decreased libido with finasteride versus placebo is 2–4 %, corresponding to 3.4–10 % of patients experiencing this side effect in treatment arms【14】.

Sexual side effects, including reduced libido, tend to diminish over time even while the drug is continued and generally resolve after the medication is stopped【14】.
Long‑term follow‑up of trial participants shows that sexual dysfunction decreases during treatment, remaining statistically significant but clinically small after the first year of therapy【14】.
Clinical evidence indicates that most men experience spontaneous improvement within the first three months after stopping finasteride【14】.

The overall rate of study discontinuation due to adverse events is ≈ 6–7 % in both the finasteride and placebo groups, suggesting that many reported side effects may not be drug‑related【14】.

Expectant management is advised for the first three months after finasteride cessation, as the majority of patients recover libido without additional intervention【14】.
When symptoms persist beyond three months, clinicians should evaluate alternative causes (e.g., depression, hypogonadism) rather than attributing them solely to finasteride, because trial data do not support persistent hormonal or enzymatic abnormalities【14】.

In clinical trials of men using finasteride 1 mg daily, the absolute incidence of erectile dysfunction ranged from 4.2 % to 15.8 %. 15
The drug produced an excess risk of 2–4 % compared with placebo across these studies. 16
The FSG‑International trial reported erectile dysfunction in 4.4 % of finasteride users versus 0.4 % on placebo. 15
The PROSPECT study observed the highest mid‑term rate, with 15.8 % of finasteride‑treated participants experiencing erectile dysfunction compared with 6.2 % in the placebo group. 15

The Prostate Cancer Prevention Trial (PCPT) showed a cumulative incidence of erectile dysfunction of 67.4 % over 7 years in finasteride‑treated men versus 61.5 % with placebo (relative risk = 1.10). This cohort was older (mean age ≈ 62–65 years) and had a high baseline prevalence of sexual dysfunction. 15

Finasteride use was associated with a mean decrease of 3.21 points on a 0–100 sexual function scale. [15][16]
By comparison, each additional year of aging contributed an average decline of 1.26 points on the same scale. [15][16]
Consequently, the impact of finasteride is roughly equivalent to 2.5 years of natural aging in terms of sexual function decline. [15][16]

Discontinuation rates due to adverse events were 6–7 % in both the finasteride and placebo groups, indicating that many reported sexual side effects may not be directly drug‑related. 16

The majority of erectile dysfunction data for finasteride derives from 5 mg studies in older men treated for benign prostatic hyperplasia (BPH). [15][16]
The 1 mg dose used for hair loss has been less extensively studied with respect to sexual side effects. 15