Finasteride in Adults 65 and Older: School, Work, and Activity Considerations

Which dose do older men take, and what do the age data cover?

Finasteride is a competitive, specific inhibitor of type II 5-alpha-reductase, the enzyme that converts testosterone to dihydrotestosterone (DHT). It is about 100-fold selective for type II over type I, and a 1 mg tablet suppresses serum DHT by 65% within 24 hours. Mean testosterone and estradiol rise by about 15% but stay within the normal range, and the drug has no affinity for the androgen receptor [2].

The 5 mg tablet (Proscar) is approved for symptomatic benign prostatic hyperplasia (BPH) in men with an enlarged prostate: it improves symptoms, reduces the risk of acute urinary retention and reduces the need for surgery such as TURP or prostatectomy, and with doxazosin it is approved to reduce the risk of symptomatic progression. It is not approved to prevent prostate cancer [1].

The 1 mg tablet (Propecia) is approved for male pattern hair loss in men only. Efficacy in bitemporal recession has not been established, and it is not indicated for women [2]. The two 1-year hair-loss trials behind that approval enrolled 1,553 men aged 18 to 41 [5]. PLESS, the 4-year BPH trial, enrolled 3,040 men aged 45 to 78 [1].

Age does change the pharmacokinetics. Mean terminal half-life is about 5 to 6 hours in men aged 18 to 60 and about 8 hours in men over 70 [2]. The type II enzyme complex itself turns over slowly, roughly 30 days, so the effect on DHT outlasts the plasma half-life considerably [2].

Dizziness, balance and falls

MTOPS randomized 3,047 men with symptomatic BPH to finasteride 5 mg (n=768), doxazosin (n=756), the combination (n=786) or placebo (n=737). Dizziness was reported by 7.4% on finasteride, 8.1% on placebo, 17.7% on doxazosin and 23.2% on the combination; postural hypotension was 9.1%, 8.0%, 16.7% and 17.8% respectively [1]. The label notes that MTOPS was not designed to make statistical comparisons between groups for reported adverse experiences [1]. On finasteride alone, the dizziness rate sat at the placebo level, and the large increase belonged to the arms containing the alpha-blocker.

A separate descriptive study of 117 hospitalized patients aged 75 and older found that 84 (71.8%) had at least one potentially inappropriate urologic prescription, and 77 of those 84 (91.7%) involved an alpha-blocker. The inappropriate-prescription group had roughly three times the odds of a history of falls (OR 3.22, 95% CI 1.08 to 10.2) [6]. Because the study was descriptive and most of the flagged prescriptions involved alpha-blockers, it does not isolate any effect of finasteride on falls [6].

Mood, memory and mentally demanding work

There is no boxed warning on either product. Depression and suicidal ideation appear in the labels' postmarketing section, not in a boxed warning or a numbered warnings subsection [2]. Since August 2022 the Propecia label reads 'depression, suicidal ideation and behavior'; the labels state that these reports are voluntary, come from a population of uncertain size, and cannot establish a causal relationship [2][7].

Two large cohorts of older men put numbers on the association. In Ontario, 93,197 men aged 66 or older starting a 5-alpha reductase inhibitor, mostly for BPH, were compared with matched unexposed men: depression hazard ratio 1.94 (95% CI 1.73 to 2.16) in the first 18 months and 1.22 (1.08 to 1.37) afterward, self-harm 1.88 (1.34 to 2.64) in the first 18 months only, and suicide 0.88 (0.53 to 1.45). The absolute increases were 237 depression diagnoses and 17 self-harm events per 100,000 patient-years [3]. In Sweden, among 2,236,876 men aged 50 to 90 (70,645 starting finasteride, median age at treatment 73), the depression hazard ratio was 1.61 (1.48 to 1.75) and suicide was not associated (HR 1.22, 95% CI 0.99 to 1.49). The dementia association faded over time, which the authors suggested may partly reflect more dementia detection in men with BPH [8].

For cognition, one randomized 1-year 2x2 factorial trial studied 60 men aged 60 or older with low testosterone, given testosterone or vehicle paired with finasteride 5 mg or placebo. Major cognitive improvements were not seen with either drug; finasteride produced a small increase in performance on the Benton Judgment of Line Orientation test [9].

Exercise, sport and driving

Finasteride and dutasteride are not named anywhere in the WADA 2026 Prohibited List, so finasteride carries no anti-doping restriction [4].

The labels report no clinically important interactions with the cytochrome P450 system and no clinically significant adverse interactions in studies where finasteride was used alongside ACE inhibitors, beta blockers, calcium channel blockers, diuretics, nitrates, benzodiazepines, anticonvulsants, NSAIDs and quinolone antibiotics [2][1].

For driving and activity, the MTOPS figures are the relevant numbers. Somnolence was 1.7% on finasteride, 1.5% on placebo and 3.1% on the combination with doxazosin, and the doxazosin-containing arms had the highest dizziness and postural hypotension rates [1].

Sexual side effects

In PLESS, year-1 rates on 5 mg versus placebo were impotence 8.1% vs 3.7%, decreased libido 6.4% vs 3.4%, decreased ejaculate volume 3.7% vs 0.8% and ejaculation disorder 0.8% vs 0.1%; in years 2 to 4 there was no significant difference between groups (impotence 5.1% vs 5.1%, libido 2.6% vs 2.6%). Discontinuation for sexual adverse reactions was 3.7% vs 2.1% [1].

On 1 mg, across three 12-month trials in 945 treated and 934 placebo men aged 18 to 41, 3.8% reported one or more sexual adverse events vs 2.1% on placebo (p=0.04); decreased libido was 1.8% vs 1.3%, erectile dysfunction 1.3% vs 0.7% and ejaculation disorder 1.2% vs 0.7%, and each rate fell to 0.3% or less by year 5 [2]. A meta-analysis of 15 randomized placebo-controlled trials in 4,495 men with androgenetic alopecia found a relative risk of sexual dysfunction of 1.66 (95% CI 1.20 to 2.30) for finasteride 1 mg [10].

The labels also list sexual dysfunction that continued after stopping (erectile dysfunction, libido disorders, ejaculation and orgasm disorders) and male infertility or poor seminal quality, with normalization reported after discontinuation [2]. One interview study of 71 otherwise healthy men aged 21 to 46 who reported sexual side effects lasting at least 3 months after stopping (mean use 28 months, mean persistence 40 months) cannot establish frequency or cause because participants were self-selected and reporting from memory [11]. On 5 mg, median ejaculate volume fell 0.6 mL (22.1%) over 24 weeks in healthy volunteers, was reversible, and took an average of 84 weeks to return to baseline [1].

PSA: the routine test that changes

On 5 mg, PSA is about 50% lower within six months. The Proscar label says to establish a new PSA baseline at least six months after starting treatment, to double an isolated PSA value after six months for comparison with untreated ranges, and to evaluate any confirmed rise from the lowest value even if it is still within the normal range. It also says percent free PSA remains constant and needs no adjustment [1].

Propecia's effect is smaller: mean PSA fell from 0.7 to 0.5 ng/mL at month 12 in men aged 18 to 41 [2]. Both labels carry the high-grade prostate cancer warning. In the 7-year Prostate Cancer Prevention Trial of 18,882 men aged 55 or older on finasteride 5 mg, Gleason 8 to 10 cancer occurred in 1.8% vs 1.1% on placebo, while overall prostate cancer detection was 18.4% vs 24.4% [1][12]. Proscar is not approved to prevent prostate cancer [1], and the Propecia label states that the clinical significance of the high-grade finding for 1 mg users is unknown [2].

1 mg or 5 mg after 65?

The two tablets are not interchangeable doses of one treatment: 5 mg is for BPH and 1 mg is for hair loss [2][1]. PSA interpretation differs too, by about half on 5 mg and by a few tenths of a point on 1 mg [2][1]. HealthRX.com offers finasteride 1 mg for male pattern hair loss.