Finasteride Geriatric (65+) Dosing: What Older Adults Need to Know

Does finasteride need a lower dose after 65?

The Propecia dosing section reads: one 1 mg tablet once daily, with or without meals [1]. The Proscar section reads: one 5 mg tablet once a day, alone or with the alpha-blocker doxazosin [2]. Neither dosing section gives an age- or weight-based step-down [1][2]. The geriatric-use sections say no dosage adjustment is necessary in the elderly. The Propecia label adds that its clinical efficacy studies did not include subjects aged 65 and over and that efficacy in the elderly has not been established [1]. The Proscar label reports that 1,480 PLESS participants were 65 or older and 105 were 75 or older, with no overall differences in safety or effectiveness compared with younger men [2].

The aging question mostly comes down to how long the drug stays in the body. 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]. A pharmacokinetic review of finasteride put the same point plainly: half-life values are higher in elderly men, but no dosage adjustments are necessary [4].

Kidney function does not change the dose either. Both labels state that no dosage adjustment is necessary in renal impairment [1][2], and the pharmacokinetic review explains that the metabolites that accumulate are relatively inactive and that greater faecal excretion of metabolites occurs in those patients [4]. For the liver, both labels say caution should be exercised in patients with liver function abnormalities because finasteride is metabolized extensively in the liver, and that the effect of hepatic impairment on finasteride pharmacokinetics has not been studied [1][2].

The 5 mg dose for BPH in older men

Proscar is indicated for symptomatic BPH in men with an enlarged prostate — to improve symptoms, reduce the risk of acute urinary retention and reduce the risk of surgery [2]. It is not approved to prevent prostate cancer [2].

The trial behind those claims, PLESS, enrolled 3,040 men aged 45 to 78 and ran for four years. Finasteride 5 mg reduced the risk of surgery by 55% (95% CI 41 to 65) and the risk of acute urinary retention by 57% (95% CI 40 to 69) compared with placebo [6]. Mean symptom score fell 3.3 points on finasteride versus 1.3 points on placebo, and prostate volume was significantly reduced [6].

Adding an alpha-blocker changes the numbers. In MTOPS (3,047 men), overall clinical progression of BPH was reduced by 66% with finasteride plus doxazosin versus placebo, by 34% with finasteride alone and by 39% with doxazosin alone [7]. The trade-off shows up in the trial's blood pressure table: postural hypotension was reported in 17.8% of men on combination therapy, 9.1% on finasteride alone, 16.7% on doxazosin alone and 8.0% on placebo, with dizziness in 23.2%, 7.4%, 17.7% and 8.1% respectively [2].

Before treatment starts, the Proscar label also asks that other urological conditions causing similar symptoms be considered, notes that prostate cancer and BPH can coexist, and says men with large residual urinary volume or severely diminished urinary flow should be monitored for obstructive uropathy [2].

Reading PSA in an older man on finasteride

The Proscar label gives specific instructions. PSA falls by approximately 50% within six months of starting the 5 mg dose. A new PSA baseline should be established at least six months after starting and PSA monitored periodically thereafter. To interpret an isolated PSA value in a man treated for six months or more, the value should be doubled for comparison with normal ranges in untreated men. Any confirmed increase from the lowest PSA value while on treatment may signal prostate cancer and should be evaluated, even if the number is still within the normal range for untreated men. Percent free PSA stays constant, so no adjustment to it appears necessary [2].

The 1 mg label describes its own data rather than a doubling rule: in men aged 18 to 41, mean PSA fell from 0.7 to 0.5 ng/mL by month 12, and any confirmed increase from the lowest value while on treatment should be evaluated [1]. The doubling instruction is written in the 5 mg label [2].

High-grade prostate cancer is a separate issue. In the 7-year Prostate Cancer Prevention Trial of 18,882 men aged 55 and older, Gleason score 8 to 10 cancer was found in 1.8% of men on finasteride 5 mg versus 1.1% on placebo [2]. Overall prostate cancer was detected in 18.4% versus 24.4%, a 24.8% relative reduction [8]. The labels state that 5-alpha reductase inhibitors may increase the risk of high-grade prostate cancer [1][2], and the Propecia label states that the clinical significance of the finding for men taking 1 mg is unknown [1].

The 1 mg hair-loss dose after 65

Propecia is indicated for male pattern hair loss in men only, and efficacy in bitemporal recession has not been established [1][9]. The Propecia label states that its clinical efficacy studies did not include subjects aged 65 and over and that efficacy in the elderly has not been established [1]. The supporting trials were two 1-year placebo-controlled studies of 1,553 men aged 18 to 41, with 1,215 continuing into a second blinded year. Hair count in a 1-inch circle of vertex scalp was 107 hairs higher than placebo at 1 year and 138 higher at 2 years (P<0.001) [5].

The label reports that a 1 mg tablet suppresses serum DHT by 65% within 24 hours, while mean testosterone and estradiol rise by about 15% and remain within the normal range [1].

The label sets expectations on timing: daily use for three months or more is usually needed before benefit is seen, continued use is recommended to sustain it, and withdrawal leads to reversal of effect within 12 months [1].

HealthRX.com offers finasteride 1 mg by prescription.

Side effects in older men

In PLESS, the men were 45 to 78 and the first-year rates on 5 mg versus placebo were: impotence 8.1% versus 3.7%, decreased libido 6.4% versus 3.4%, and decreased ejaculate volume 3.7% versus 0.8%. In years 2 to 4 there was no significant difference between the groups in impotence, decreased libido or ejaculation disorder [2].

In the 12-month Propecia trials in men aged 18 to 41, decreased libido was 1.8% versus 1.3%, erectile dysfunction 1.3% versus 0.7% and ejaculation disorder 1.2% versus 0.7%, with 3.8% of treated men reporting at least one of these versus 2.1% on placebo (p=0.04). By year 5 each rate had fallen to 0.3% or less [1]. The labels caution that rates from different clinical trials cannot be directly compared. A meta-analysis of 15 randomized trials covering 4,495 men found a relative risk of sexual dysfunction of 1.57 (95% CI 1.19 to 2.08) with these drugs [10].

In PLESS, breast enlargement occurred in 0.5% of men taking finasteride and 0.1% taking placebo during year 1, and in 1.8% and 1.1%, respectively, during years 2 through 4. Breast tenderness occurred in 0.4% and 0.1% during year 1, and 0.7% and 0.3% during years 2 through 4 [2]. In MTOPS, gynecomastia was reported by 2.2% of men on finasteride versus 0.7% on placebo [2]. In the Propecia trials, breast tenderness and enlargement were no more common than on placebo [1]. Male breast cancer appears as a postmarketing report, with the relationship to long-term use unknown [2].

Mood is where labels and cohort data diverge in strength. There is no boxed warning on either product [1][2]. The postmarketing section lists depression, suicidal ideation and behavior, with the labels' caveat that these are voluntary reports from a population of uncertain size and a causal relationship cannot be reliably established [1][2][11]. The largest datasets in older men point to a modest signal: in 93,197 Ontario men aged 66 and older starting a 5-alpha reductase inhibitor, mostly for BPH, suicide was not significantly increased (HR 0.88, 95% CI 0.53 to 1.45), self-harm was higher only in the first 18 months (HR 1.88, 1.34 to 2.64), and depression was higher in the first 18 months (HR 1.94, 1.73 to 2.16) and afterward (HR 1.22, 1.08 to 1.37), with absolute increases of 17 self-harm and 237 depression cases per 100,000 patient-years [3]. In a Swedish register of 70,645 finasteride starters with a median age of 73, depression was higher (HR 1.61, 1.48 to 1.75) and suicide was not clearly associated (HR 1.22, 0.99 to 1.49) [12].

Interactions with the medicines older men take

The label states that no drug interactions of clinical importance have been identified and that finasteride does not appear to affect the cytochrome P450 system. Drugs tested in humans include antipyrine, digoxin, propranolol, theophylline and warfarin, with no clinically meaningful interactions [1].

The label also lists medicines that were used alongside finasteride in clinical studies without evidence of clinically significant adverse interactions, although dedicated interaction studies were not performed: acetaminophen, aspirin, alpha-blockers, ACE inhibitors, anticonvulsants, benzodiazepines, beta blockers, calcium channel blockers, cardiac nitrates, diuretics, H2 antagonists, statins, NSAIDs and quinolone antibiotics [2]. Warfarin is the only anticoagulant named in the interaction section [1].

Finasteride itself is metabolized mainly by CYP3A4 [1]. The label's interaction section does not address CYP3A4 inhibitors or inducers [1].

What happens when finasteride is stopped

The Propecia label recommends continued use to sustain benefit, with periodic re-evaluation, and states that withdrawal leads to reversal of effect within 12 months [1]. For PSA, the doubling rule is written for men who have taken 5 mg for six months or more [2]; the label does not say how long after stopping a man's PSA returns to his own untreated baseline.