Finasteride Adult (30 to 49) Dosing: Evidence-Based Guide

What is the finasteride dose at 30 to 49?

Two FDA-approved tablets carry the two labeled doses. Propecia, finasteride 1 mg, is one tablet once daily with or without meals for male pattern hair loss (androgenetic alopecia) in men only [1]. Proscar, finasteride 5 mg, is one tablet once daily with or without meals for symptomatic benign prostatic hyperplasia (BPH) in men with an enlarged prostate, to improve symptoms, reduce the risk of acute urinary retention and reduce the need for surgery [2].

Propecia is not indicated for women, and its efficacy in bitemporal recession has not been established [1]. The labeled hair-loss dose is one 1 mg tablet once daily for men with male pattern hair loss [1].

Does the dose change with age in your 30s and 40s?

No. Both labels give a single fixed dose for each indication, with no titration step and no age adjustment [1][2]. Being 30 rather than 49 does not change the tablet.

The supporting trial populations are worth knowing. The two pivotal hair-loss trials enrolled 1,553 men aged 18 to 41 [5], so a man in his late 40s is treated on the labeled dose rather than on trial data from his own age band. For BPH, PLESS studied men aged 45 to 78, so its results do not directly describe men younger than 45 [2].

Why 1 mg for hair and 5 mg for the prostate

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 Type II accounts for roughly two-thirds of circulating DHT [1]. A 1 mg tablet suppresses serum DHT by 65% within 24 hours, while mean testosterone and estradiol rise about 15% and stay inside the normal range [1].

Does the extra 4 mg buy more suppression? A 42-day scalp biopsy study in 249 men with androgenetic alopecia measured DHT at daily doses from 0.01 mg to 5 mg. Scalp DHT fell 64.1% at 1 mg and 69.4% at 5 mg; serum DHT fell 71.4% at 1 mg and 72.2% at 5 mg. The authors concluded that doses as low as 0.2 mg per day maximally decreased both [6]. In two separate dose-ranging hair studies, 1 mg and 5 mg showed similar efficacy that was superior to lower doses, and 1 mg a day was identified as the optimal dose [17].

The enzyme complex turns over slowly, roughly 30 days for Type II, so the effect on DHT outlasts the plasma half-life of about 5 to 6 hours in men aged 18 to 60 [1]. The labeled schedule is one tablet daily: 1 mg for male pattern hair loss and 5 mg for symptomatic BPH [1][2].

What the 1 mg hair-loss trial found

In two 1-year placebo-controlled trials, 1,553 men aged 18 to 41 with male pattern hair loss took finasteride 1 mg daily or placebo, and 1,215 continued into blinded 12-month extensions. Hair count in a 1-inch (5.1 cm2) circle of balding vertex scalp, from a baseline of 876 hairs, was 107 hairs higher than placebo at 1 year and 138 higher at 2 years (P<0.001). The placebo group kept losing hair [5]. The label states that efficacy in bitemporal recession has not been established [1].

What the 5 mg BPH evidence covers

PLESS randomized 3,040 men aged 45 to 78 with moderate-to-severe symptoms and an enlarged prostate to finasteride 5 mg or placebo for 4 years (1,524 vs 1,516) [2]. The labeled claims come from that program: symptom improvement, fewer episodes of acute urinary retention, and less need for TURP or prostatectomy [2]. Proscar with the alpha-blocker doxazosin is also labeled to reduce the risk of symptomatic progression, defined as a confirmed 4-point or greater rise in AUA symptom score [2]. Proscar is not approved to prevent prostate cancer, and the label states that limitation directly [2].

Side effects at each dose

At 1 mg, three 12-month controlled trials enrolled 945 men on finasteride and 934 on placebo, aged 18 to 41. Drug-related decreased libido was 1.8% vs 1.3%, erectile dysfunction 1.3% vs 0.7%, and ejaculation disorder 1.2% vs 0.7%. Overall, 3.8% (36 of 945) reported one or more of these against 2.1% (20 of 934) on placebo (p=0.04). Discontinuation for drug-related sexual events was 1.2% vs 0.9%, and the incidence of each reaction fell to 0.3% or lower by year 5 [1]. A self-administered sexual function questionnaire at month 12 favored placebo in 3 of 4 domains: sexual interest, erections and perception of sexual problems [1].

A 2019 meta-analysis of 15 randomized placebo-controlled trials in 4,495 men put the relative risk of sexual dysfunction at 1.66 for finasteride 1 mg (95% CI 1.20 to 2.30) [7]. A separate review of 34 finasteride hair-loss trials found that none had adequate safety reporting, 76% evaluated safety for a year or less, and funnel plots suggested under-detection of sexual adverse effects [8].

At 5 mg, PLESS year 1 results in men 45 to 78 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 for impotence (5.1% vs 5.1%) or decreased libido (2.6% vs 2.6%). Discontinuation for sexual adverse reactions was 3.7% vs 2.1% [2].

The current Propecia label also lists, in its postmarketing section, sexual dysfunction that continued after discontinuation, including erectile dysfunction, libido disorders, ejaculation disorders and orgasm disorders [1]. The Propecia label says these reports are voluntary and cannot reliably establish their frequency or whether finasteride caused them [1]. A 2011 interview study of 71 men who reported persistent sexual dysfunction after finasteride for hair loss (mean use 28 months, mean persistence 40 months) was self-selected and cannot show how often this happens [9].

Depression and suicidal ideation: what the labels say

There is no boxed warning on Propecia or Proscar [1][2]. Depression and suicidal ideation sit in the postmarketing section. 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, sexual dysfunction and psychoneurocognitive events, and supplement S-030, approved 08/01/2022, changed the wording to depression, suicidal ideation and behavior [10]. The labels state these reports are voluntary, come from a population of uncertain size, and cannot reliably establish a causal relationship [1][2].

The cohort data come from older men (median age 75 in Ontario; 73 at treatment start in Sweden). Among 93,197 Ontario men aged 66 or older, suicide was not increased (HR 0.88, 95% CI 0.53 to 1.45); self-harm was higher in the first 18 months (HR 1.88, 1.34 to 2.64), and depression was higher both in the first 18 months (HR 1.94, 1.73 to 2.16) and afterward (HR 1.22, 1.08 to 1.37) [11]. In 2,236,876 Swedish men aged 50 to 90, finasteride was associated with depression (HR 1.61, 1.48 to 1.75) but not with suicide (HR 1.22, 0.99 to 1.49) [12].

PSA and prostate cancer at each dose

The Propecia label reports mean PSA falling from 0.7 to 0.5 ng/mL at month 12 in men aged 18 to 41, and says any confirmed increase from the lowest value on treatment should be evaluated even if it is still within the normal range for untreated men [1]. The Proscar label reports an approximately 50% PSA decrease within six months. It says that a new baseline should be established after at least six months of treatment and that an isolated PSA value after six months or more should be doubled when compared with ranges for untreated men [2].

The high-grade prostate cancer warning comes from the 7-year Prostate Cancer Prevention Trial in 18,882 men aged 55 or older taking 5 mg: Gleason 8 to 10 cancer occurred in 1.8% vs 1.1% on placebo [2]. Overall prostate cancer was less common on finasteride, 18.4% vs 24.4%, a 24.8% relative reduction [13]. With up to 18 years of follow-up, high-grade cancer (Gleason 7 to 10) remained slightly more frequent (3.5% vs 3.0%, relative risk 1.17, 95% CI 1.00 to 1.37) while 15-year survival did not differ (78.0% vs 78.2%) [14]. The labels state that whether the effect on prostate volume or study-related factors explain the high-grade finding has not been established [1][2], and the Propecia label states that the clinical significance for men taking 1 mg is unknown [1].

Fertility, semen and pregnancy exposure

Proscar's label reports that 24 weeks of treatment in healthy volunteers had no clinically meaningful effect on sperm concentration, motility, morphology or pH, but median ejaculate volume fell 0.6 mL (22.1%); this was reversible, with an average 84 weeks to return to baseline [2]. For Propecia 1 mg, median ejaculate volume fell 0.3 mL (11%) after 48 weeks, compared with 0.2 mL (8%) on placebo [1]. A separate randomized trial of 99 healthy men found total sperm count on finasteride 5 mg was significantly lower than baseline at 26 weeks (-34.3%) but not at 52 weeks (-16.2%) or 24 weeks after stopping (-6.2%); the 52-week change in sperm concentration (-7.4%) was not significant [15]. The Propecia label's postmarketing section lists male infertility and poor seminal quality, with normalization or improvement reported after discontinuation [1].

Finasteride is contraindicated in women who are or may be pregnant, and women who are pregnant or may be pregnant should not handle crushed or broken tablets because of the risk of abnormal external genitalia in a male fetus; the coating prevents contact with the active ingredient when tablets are intact [1]. The Proscar label notes that the highest amount of finasteride measured in semen was 50- to 100-fold below the dose that had no effect on circulating DHT in men [2].

Drug interactions

The Propecia label states that no drug interactions of clinical importance have been identified and that finasteride does not appear to affect the cytochrome P450 system; compounds tested in man include antipyrine, digoxin, propranolol, theophylline and warfarin, with no clinically meaningful interactions found [1]. In clinical studies it was used alongside ACE inhibitors, alpha-blockers, benzodiazepines, beta blockers, calcium channel blockers, diuretics, H2 antagonists, statins, NSAIDs and quinolone antibiotics without evidence of clinically significant adverse interactions [1].

Combining finasteride with minoxidil

In a 12-month randomized study of 450 Chinese men with male pattern hair loss, 80.5% of those on finasteride 1 mg, 59% of those on 5% topical minoxidil and 94.1% of those on both showed improvement. Randomization was 160, 130 and 160 men, with 428 evaluated at the end [16].