How to Safely Stop Finasteride: An Evidence-Based Discontinuation Guide

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Does finasteride need to be tapered?

The Propecia dosage section lists one 1 mg tablet once daily, with or without food, and states that continued use is recommended to sustain benefit, which should be re-evaluated periodically; withdrawal of treatment leads to reversal of effect within 12 months [1]. It describes no step-down. The Proscar dosage section lists one 5 mg tablet once daily, alone or with the alpha-blocker doxazosin [2]. Neither label sets out a tapering schedule.

The drug itself clears quickly. Mean terminal half-life is about 5 to 6 hours in men 18 to 60 and about 8 hours in men over 70 [1]. The enzyme it blocks turns over slowly, with a half-life of roughly 30 days for the Type II 5-alpha-reductase complex, so the effect on DHT lasts well beyond the plasma half-life [1].

Stopping 1 mg for hair loss

Sustained hair benefit is the stated reason the label recommends continued use, and the same label says withdrawal leads to reversal of effect within 12 months [1]. In the label's trials, a change from Propecia to placebo (n=48) at the end of the first 12 months resulted in reversal of the hair-count increase 12 months later, at 24 months [1]. The label does not name a month at which shedding starts.

The Proscar label reports that in healthy male volunteers treated with Proscar (5 mg) for 14 days, discontinuation resulted in a return of DHT levels to pretreatment levels in approximately 2 weeks [2].

The trial data behind the 1 mg dose come from two 1-year placebo-controlled trials in 1553 men aged 18 to 41, with 1215 men continuing into blinded second-year extensions. Hair count in a 1-inch (5.1 cm2) circle of 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), while the placebo group kept losing hair [4]. The label notes that daily use for three months or more is usually needed before benefit is seen [1].

Stopping 5 mg for BPH

Proscar is indicated to improve symptoms of benign prostatic hyperplasia in men with an enlarged prostate, to reduce the risk of acute urinary retention and to reduce the need for surgery such as TURP or prostatectomy [2]. A withdrawal study found prostate regrowth and worsening symptom scores after the 5-alpha-reductase inhibitor was stopped [3].

The clearest withdrawal data come from a prospective study of 120 men with BPH, randomized to finasteride 5 mg or dutasteride 0.5 mg, each combined with an alpha-blocker, for one year, then continued on the alpha-blocker alone for a second year [3]. Prostate volume fell 24.5% ± 10.01% in the finasteride arm at one year, then rose 20.7% ± 14.1% in the year after the 5-alpha-reductase inhibitor was withdrawn; the dutasteride arm rose 18.6% ± 7.4%. International Prostate Symptom Scores deteriorated significantly in both groups after withdrawal [3]. Both arms stayed on an alpha-blocker throughout, and the study did not test what happens when finasteride alone is stopped.

PSA after stopping

The Proscar label says finasteride reduces serum PSA by approximately 50% within six months of treatment, that a new baseline should be established at least six months after starting, and that an isolated PSA value in a man treated for six months or more should be doubled for comparison with normal ranges in untreated men [2]. Percent free PSA is unchanged by the drug [2]. In men aged 18 to 41 taking 1 mg, mean PSA fell from 0.7 to 0.5 ng/mL at month 12 [1].

Those instructions are written for men taking the drug. In a 48-week trial of finasteride 1 mg in 181 men aged 19 to 41, the small decrease in serum PSA (-0.2 ng/mL) reversed on discontinuation [11].

Sexual side effects after stopping

In the three 12-month Propecia trials (945 men on finasteride, 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%; 3.8% versus 2.1% reported at least one of these (p=0.04), and each rate fell to 0.3% or lower by year five [1]. A meta-analysis of 15 placebo-controlled trials in 4,495 men with androgenetic alopecia put the relative risk of sexual dysfunction on finasteride at 1.66 (95% CI 1.20 to 2.30) [5].

The Propecia postmarketing section lists 'sexual dysfunction that continued after discontinuation of treatment, including erectile dysfunction, libido disorders, ejaculation disorders, and orgasm disorders' [1]. The label reports persistent sexual dysfunction after discontinuation among postmarketing events, but it does not quantify how frequently the persistent form occurs. Safety reporting in this field has been criticized: a review of 34 finasteride trials for hair loss found none with adequate safety reporting and 76% that evaluated safety for a year or less [6]. Standardized interviews with 71 otherwise healthy men who reported sexual symptoms lasting at least three months after stopping found a mean persistence of 40 months; the men were self-selected and the design cannot establish frequency or cause [7].

Mood-related reports

Neither Propecia nor Proscar carries a boxed warning; depression and suicidal ideation appear in the postmarketing section [1][2]. The current Propecia wording follows a May 31, 2022 FDA safety labeling change order and the August 1, 2022 supplement that changed the entry to 'depression, suicidal ideation and behavior' [8]. The labels state that these reports are voluntary, come from a population of uncertain size, and that a causal relationship cannot reliably be established [1][2].

Population data are mixed. Among 93,197 Ontario men aged 66 or older starting a 5-alpha-reductase inhibitor, mostly for BPH, suicide risk was not raised (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 roughly doubled in that period (HR 1.94, 1.73 to 2.16) [9]. In 2,236,876 Swedish men aged 50 to 90, finasteride was associated with depression (HR 1.61, 1.48 to 1.75) and not significantly with suicide (HR 1.22, 0.99 to 1.49) [10]. Both cohorts were of older men (median age 75 in Ontario; 73 at treatment start in Sweden), not younger men taking 1 mg for hair.

Semen, fertility and stopping

The Proscar label reports a 24-week semen study in healthy volunteers with no clinically meaningful effect on sperm concentration, motility, morphology or pH, but a median ejaculate volume decrease of 0.6 mL (22.1%), reversible after discontinuation with an average of 84 weeks to return to baseline [2]. For 1 mg, median ejaculate volume changed by -0.3 mL (-11%) versus -0.2 mL (-8%) on placebo at 48 weeks [1]. The Propecia label lists male infertility and poor seminal quality, with normalization or improvement reported after discontinuation [1].

The Propecia label states that finasteride is contraindicated in women who are or may be pregnant and that such women should not handle crushed or broken tablets, since the coating prevents contact only while tablets are intact [1].