Finasteride Geriatric (65+) Monitoring: Lab Tests, Safety Checks, and Clinical Oversight

What does the label actually ask you to monitor?

The finasteride labels' monitoring language centers on PSA. The Proscar (5 mg) label states that PSA falls by approximately 50% within six months of treatment, that this fall is predictable across the PSA range in men with symptomatic BPH although it varies between individuals, and that a new PSA baseline should be established at least six months after starting, with PSA monitored periodically after that [1]. Any confirmed increase from the lowest PSA value on treatment may signal prostate cancer and should be evaluated, even if the value is still within the normal range for men not taking a 5-alpha reductase inhibitor [1].

The same label gives the correction to use: to interpret an isolated PSA in a man who has taken Proscar for six months or more, double the value for comparison with normal ranges in untreated men [1]. The ratio of free to total PSA remains constant, so percent free PSA needs no adjustment [1]. The label also notes that missed doses can affect PSA results [1].

Neither label's warnings section sets out routine creatinine, eGFR, liver enzyme, complete blood count or standing blood-pressure testing [2][1]. The one other monitoring instruction in the Proscar label is clinical: before starting for BPH, other urological conditions that cause similar symptoms should be considered, prostate cancer and BPH may coexist, and men with a large residual urinary volume or severely diminished urinary flow should be carefully monitored for obstructive uropathy and may not be candidates for finasteride [1]. The Propecia label adds that benefit should be re-evaluated periodically [2].

Does the doubling rule apply to the 1 mg hair-loss dose?

The two labels differ here, and the difference matters to a 65-year-old taking 1 mg for hair rather than 5 mg for an enlarged prostate.

The doubling instruction appears in the Proscar 5 mg label [1]. The Propecia 1 mg label describes the PSA decrease and says that any confirmed increase from the lowest PSA value while on Propecia may signal prostate cancer and should be evaluated, but it gives no multiplication factor for the 1 mg dose [2]. What it does report is that in men aged 18 to 41 taking 1 mg, mean PSA fell from 0.7 ng/mL at baseline to 0.5 ng/mL at month 12, and it notes that the 5 mg product lowers PSA by about 50% in older men with BPH [2].

So the labeled correction is written for the 5 mg BPH product. If an older man is taking 1 mg for hair loss, the label offers no correction factor for his dose [2].

What the labels say about high-grade prostate cancer

The Prostate Cancer Prevention Trial enrolled 18,882 men aged 55 or older with a normal digital rectal examination and a PSA of 3.0 ng/mL or lower, and assigned them to finasteride 5 mg daily or placebo for seven years [3]. Prostate cancer was detected in 18.4% of the finasteride group (803 of 4,368) versus 24.4% of the placebo group (1,147 of 4,692), a 24.8% relative reduction (95% CI 18.6 to 30.6) [3]. Gleason 7 to 10 tumors were more common on finasteride, 6.4% versus 5.1% of men [3], and the labels report Gleason 8 to 10 cancer in 1.8% on finasteride versus 1.1% on placebo [1].

Both labels state that 5-alpha reductase inhibitors may increase the risk of high-grade prostate cancer, and that whether the effect of reducing prostate volume or study-related factors influenced these results has not been established [2][1]. The Propecia label says the clinical significance of these findings for men taking 1 mg is unknown [2], and the Proscar label states it is not approved to prevent prostate cancer [1].

Sexual side effects: what the trials measured

The Proscar label's four-year PLESS study enrolled 3,040 men aged 45 to 78, with 1,524 on 5 mg and 1,516 on placebo [1]. In year one, investigator-judged drug-related 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, impotence was 5.1% in both groups and decreased libido 2.6% in both [1]. Discontinuation for sexual adverse reactions was 3.7% on finasteride versus 2.1% on placebo [1].

In three 12-month trials of Propecia in 945 men on drug and 934 on placebo, all aged 18 to 41, drug-related decreased libido was 1.8% versus 1.3%, erectile dysfunction 1.3% versus 0.7%, and ejaculation disorder 1.2% versus 0.7%. One or more of these was reported by 3.8% (36 of 945) versus 2.1% (20 of 934), p=0.04, and the incidence of each fell to 0.3% or lower by year five [2].

A meta-analysis of 15 randomized placebo-controlled trials covering 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 5-alpha reductase inhibitors, and 1.66 (1.20 to 2.30) for finasteride 1 mg alone [4]. A separate review of 34 finasteride trials for hair loss found that none had adequate safety reporting, and its funnel plots suggested under-detection of sexual adverse effects [5].

The postmarketing sections of the labels list sexual dysfunction that continued after stopping treatment, including erectile dysfunction, libido, ejaculation and orgasm disorders. The labels describe these as voluntary reports from a population of uncertain size, from which a causal relationship cannot reliably be established [2][6]. The Proscar label says persistent sexual events were reported rarely in men taking 5 mg for BPH; most were older and taking other medicines, and the independent role of Proscar is unknown [1].

Depression and suicide reports in men over 65

There is no boxed warning on either product [2]. Depression and suicidal ideation and behavior sit in the postmarketing section. FDA sent a safety labeling change order on May 31, 2022, and the August 2022 supplement changed the wording to include suicidal ideation and behavior; the current labels carry the same causality caveat as the sexual reports [6][2].

The largest data in this age group come from two cohorts. In Ontario, 93,197 men aged 66 or older (median 75) who started a 5-alpha reductase inhibitor, mostly for BPH, were compared with matched unexposed men: suicide hazard ratio 0.88 (95% CI 0.53 to 1.45, no increase); self-harm hazard ratio 1.88 (1.34 to 2.64) in the first 18 months only; depression hazard ratio 1.94 (1.73 to 2.16) in the first 18 months and 1.22 (1.08 to 1.37) afterward, with absolute increases of 17 self-harm and 237 depression cases per 100,000 patient-years [7].

In a Swedish register study of 2,236,876 men aged 50 to 90, 70,645 started finasteride at a median age of 73. Depression was associated with finasteride (hazard ratio 1.61, 95% CI 1.48 to 1.75) with no clear change over time, and suicide was not associated (hazard ratio 1.22, 0.99 to 1.49) [8]. Both studies describe associations in older men, mostly treated for prostate symptoms, and neither can establish cause.

Blood pressure and alpha-blockers

The Medical Therapy of Prostatic Symptoms study enrolled 3,047 men for 4 to 6 years. Combination therapy with finasteride plus doxazosin reduced overall clinical progression by 66% compared with placebo, and finasteride alone by 34% [9].

The Proscar safety table from that study lists investigator-judged drug-related postural hypotension in 8.0% on placebo, 16.7% on doxazosin, 9.1% on finasteride alone and 17.8% on the combination, with dizziness in 8.1%, 17.7%, 7.4% and 23.2% respectively [1]. Those are reported adverse experiences, not measured standing blood pressures.

Drug interactions in a long medication list

The interaction section states that no drug interactions of clinical importance have been identified and that finasteride does not appear to affect the cytochrome P450 system. Antipyrine, digoxin, propranolol, theophylline and warfarin were tested with no clinically meaningful interactions [2][1]. In clinical studies, finasteride was used alongside acetaminophen, aspirin, alpha-blockers, ACE inhibitors, anticonvulsants, benzodiazepines, beta blockers, calcium channel blockers, cardiac nitrates, diuretics, H2 antagonists, statins, NSAIDs and quinolone antibiotics without evidence of clinically significant adverse interactions [1].

Finasteride is extensively metabolized in the liver, mainly by CYP3A4 [2]. The interaction section does not discuss CYP3A4 inhibitors or inducers, so the labels give no guidance on that pairing [2].

Re-evaluating whether it is still needed

The Propecia label says daily use for three months or more is usually needed before benefit appears, that continued use is recommended to sustain benefit, and that benefit should be re-evaluated periodically; stopping leads to reversal of effect within 12 months [2]. The hair-loss trials behind that label enrolled men aged 18 to 41, so the labeled efficacy data do not include men over 65 [2].

For BPH the Proscar label gives 5 mg once daily and lists improving symptoms, reducing acute urinary retention and reducing the need for surgery among the labeled benefits [1].