Finasteride Dosing for Adults Ages 50 to 64: A Clinical Guide

Does the finasteride dose change between 50 and 64?

No. Both labels specify a single once-daily dose for adult men, and the dose follows the indication rather than the birthday [1][2].

Finasteride 1 mg is Propecia, indicated for male pattern hair loss in men only; the label states that efficacy in bitemporal recession has not been established and that the drug is not indicated for women [1]. Finasteride 5 mg is Proscar, indicated for symptomatic BPH in men with an enlarged prostate to improve symptoms and reduce the risk of acute urinary retention and of surgery [2]. The BPH tablet is five times the hair-loss tablet [1][2].

Both strengths are taken with or without meals [1][2].

What the 1 mg hair-loss evidence covers

The label's efficacy data come from three 12-month trials in 1,879 men aged 18 to 41 with mild to moderate hair loss, and the two vertex trials enrolled 1,553 of them [1][3]. Of those who finished the first year, 1,215 continued into blinded second-year extensions [3]. Hair count in a 5.1 cm2 circle of vertex scalp rose 107 hairs above placebo at one year and 138 above placebo at two years (P<0.001) from a baseline of 876 hairs, while the placebo group kept thinning [3].

On mechanism, a 1 mg tablet suppresses serum DHT by about 65% within 24 hours; mean testosterone and estradiol rise about 15% but stay within the normal range; the drug has no affinity for the androgen receptor [1]. The label says daily use for three months or more is generally needed before benefit is observed, continued use is needed to sustain it, and withdrawal leads to reversal of effect within 12 months [1].

The 5 mg BPH dose in this age group

PLESS randomized 3,040 men aged 45 to 78 with moderate to severe symptoms and an enlarged prostate to four years of finasteride 5 mg or placebo [4]. Surgery was performed in 69 of 1,513 men on finasteride (5%) versus 152 of 1,503 on placebo (10%) (55% risk reduction, 95% CI 41 to 65), acute urinary retention occurred in 3% versus 7% (57% reduction, 95% CI 40 to 69), and mean symptom score fell 3.3 versus 1.3 points on a 1-to-34 scale [4].

MTOPS enrolled 3,047 men and measured overall clinical progression: 34% risk reduction with finasteride alone, 39% with doxazosin alone, and 66% with the two combined, each versus placebo [5].

PSA after 50: reading the number while on treatment

The Proscar label says PSA falls by approximately 50% within six months of treatment [2]. The label says a new PSA baseline should be established at least six months after starting and PSA monitored periodically thereafter; for an isolated value in a man treated for six months or more, values should be doubled for comparison with normal ranges in untreated men, and that percent free PSA remains constant, with no adjustment to it appearing necessary [2]. The label says that any confirmed increase from the lowest PSA value while on treatment may signal prostate cancer and should be evaluated, even if the value is still within the normal range for untreated men [2].

The 1 mg label gives the same instruction to evaluate any confirmed rise from the lowest value, and reports mean PSA going from 0.7 to 0.5 ng/mL at month 12 in men aged 18 to 41 [1].

The high-grade prostate cancer warning

The Prostate Cancer Prevention Trial assigned 18,882 men aged 55 or older with a normal digital rectal exam and PSA of 3.0 ng/mL or lower to finasteride 5 mg or placebo for seven years [2][6]. Gleason score 8 to 10 cancer was found in 1.8% of men on finasteride versus 1.1% on placebo [2]. Overall prostate cancer was detected in 18.4% versus 24.4%, a 24.8% relative reduction (95% CI 18.6 to 30.6) [6], while Gleason 7 to 10 tumors were more common on finasteride (6.4% versus 5.1% of men) [6].

The label states that 5-alpha reductase inhibitors may increase the risk of high-grade prostate cancer, that whether the effect on prostate volume or study-related factors influenced these results has not been established, and that Proscar is not approved to prevent prostate cancer [2]. The PCPT enrolled men aged 55 and older, so it did not include men aged 50 to 54 [6]. It studied finasteride 5 mg; the Propecia label says the clinical significance of the high-grade cancer findings for men taking 1 mg is unknown [1].

Sexual side effects: the numbers for each dose

At 1 mg, across three 12-month controlled trials (945 men on drug, 934 on placebo), drug-related decreased libido was reported by 1.8% versus 1.3%, erectile dysfunction by 1.3% versus 0.7%, and ejaculation disorder by 1.2% versus 0.7%; one or more of these occurred in 3.8% versus 2.1% (p=0.04), discontinuation for sexual events was 1.2% versus 0.9%, and each incidence fell to 0.3% or lower by year five [1]. A self-administered sexual function questionnaire at month 12 favored placebo in three of four domains [1].

At 5 mg in PLESS year one, impotence was 8.1% versus 3.7%, decreased libido 6.4% versus 3.4%, decreased ejaculate volume 3.7% versus 0.8%, and ejaculation disorder 0.8% versus 0.1%; in years two to four there was no significant difference in impotence, decreased libido or ejaculation disorder [2].

A meta-analysis of 15 randomized placebo-controlled trials in 4,495 men treated for androgenetic alopecia found a relative risk of sexual dysfunction of 1.57 (95% CI 1.19 to 2.08), with 1.66 (1.20 to 2.30) for finasteride 1 mg [7]. A separate review of 34 finasteride hair-loss trials found that none had adequate safety reporting and 76% evaluated safety for one year or less, with funnel plots suggesting under-detection of sexual adverse effects [8].

The postmarketing sections list sexual dysfunction that continued after discontinuation, including erectile dysfunction, libido disorders, ejaculation disorders and orgasm disorders, plus male infertility or poor seminal quality [1]. The Proscar label says persistent sexual side effects were reported rarely, most affected men were older and taking other medicines, and Proscar's independent role is unknown [2]. The labels describe postmarketing reports as voluntary, from a population of uncertain size, with a causal relationship that cannot be reliably established [1][2].

On semen, in a trial that randomized 181 men aged 19 to 41 to finasteride 1 mg or placebo for 48 weeks, finasteride produced no significant effect on sperm concentration, total sperm per ejaculate, motility or morphology, with ejaculate volume falling 0.3 mL (11%) versus 0.2 mL (8%) on placebo [10]. The Proscar label reports no clinically meaningful effect on sperm concentration, motility, morphology or pH after 24 weeks, but a 0.6 mL (22.1%) median fall in ejaculate volume, reversible with an average 84 weeks to return to baseline [2].

Mood and depression reports

Neither label carries a boxed warning [1][2]. Depression, suicidal ideation and behavior appear in the postmarketing section of the Propecia label [1]. The Proscar label lists male breast cancer among its postmarketing reports [2]. The history in the labeling: the June 2021 Propecia label listed postmarketing depression; on May 31, 2022 the FDA issued a safety labeling change order citing new information on suicidal ideation and behavior, additional sexual dysfunction and psychoneurocognitive events; supplement S-030, approved 08/01/2022, changed the wording to depression, suicidal ideation and behavior [9]. The labels describe these as voluntary reports from a population of uncertain size, from which a causal relationship cannot reliably be established [1][2].

Two large cohorts in older men are relevant to this age band. In Ontario, 93,197 men aged 66 or older starting a 5-alpha reductase inhibitor, mostly for BPH, showed no increase in suicide (HR 0.88, 95% CI 0.53 to 1.45), a higher risk of self-harm confined to the first 18 months (HR 1.88, 1.34 to 2.64), and higher depression risk (HR 1.94, 1.73 to 2.16 in the first 18 months; 1.22, 1.08 to 1.37 afterward), with absolute increases of 17 self-harm and 237 depression cases per 100,000 patient-years [11]. The Ontario cohort enrolled men aged 66 or older, so it did not study men aged 50 to 64 [11]. A Swedish register study of 2,236,876 men aged 50 to 90, including 70,645 who started finasteride at a median age of 73, found depression HR 1.61 (1.48 to 1.75) with no clear rise over time, and no significant suicide association (HR 1.22, 0.99 to 1.49) [12]. The Swedish cohort included men aged 50 to 90, although men starting finasteride had a median age of 73 [12]. Both cohorts are dominated by older men treated for prostate symptoms rather than hair loss.

Other medicines at 50-plus

The labels report no clinically important drug interactions, state that finasteride does not appear to affect the cytochrome P450 system, and note that antipyrine, digoxin, propranolol, theophylline and warfarin were tested without clinically meaningful interactions [1][2]. Finasteride was also used in clinical studies alongside ACE inhibitors, alpha-blockers, beta blockers, calcium channel blockers, diuretics, HMG-CoA reductase inhibitors, NSAIDs, benzodiazepines and quinolones without evidence of clinically significant adverse interactions [2].

In MTOPS, drug-related postural hypotension was reported in 16.7% of men taking doxazosin alone and 17.8% taking doxazosin with finasteride, versus 9.1% on finasteride alone and 8.0% on placebo [2].

On CYP3A4, finasteride is metabolized mainly by that enzyme, but inhibitors and inducers of CYP3A4 are not discussed in the interaction section of the label [1].

Timing, half-life and household handling

The mean terminal half-life is about 5 to 6 hours in men aged 18 to 60 and about 8 hours in men over 70 [1]. Because the Type II enzyme complex turns over slowly, roughly 30 days, the effect on DHT outlasts the plasma half-life [1].

Pregnancy is a contraindication, and the Propecia label carries Pregnancy Category X [1]. The label says women who are or may be pregnant must not handle crushed or broken tablets, because of the risk of abnormal external genitalia in a male fetus; intact coated tablets prevent contact with the active ingredient during normal handling [1]. The Proscar label notes that women could also be exposed through semen, and that the highest amount measured in semen was estimated to be 50- to 100-fold less than the 5 microgram dose of finasteride that had no effect on circulating DHT in men [2].

Propecia is a prescription-only 1 mg oral tablet, and Proscar is a prescription-only 5 mg oral tablet [13][14].