Finasteride Side Effects: Withdrawal and Discontinuation Syndrome Explained

Is there a finasteride withdrawal syndrome?

The Propecia label describes no withdrawal reaction; its dosing is one 1 mg tablet once daily, with or without food [1]. What men are usually looking for under the word withdrawal is side effects that were present during treatment and did not clear after the drug stopped. The label's wording for that is 'sexual dysfunction that continued after discontinuation of treatment, including erectile dysfunction, libido disorders, ejaculation disorders, and orgasm disorders' [1]. The term post-finasteride syndrome is the name used in the literature for that cluster.

What happens in the body when the drug stops

Finasteride inhibits Type II 5-alpha-reductase, the enzyme that converts testosterone to dihydrotestosterone (DHT) [1]. A 1 mg tablet suppresses serum DHT by 65% within 24 hours [1]. The drug itself clears quickly — mean terminal half-life about 5 to 6 hours in men 18 to 60 and about 8 hours in men over 70 [1] — but the enzyme complex it blocks turns over slowly, with a half-life of about 30 days for Type II [1]. That is why the hormonal effect lingers well past the last tablet even though blood levels of finasteride do not.

For 5 mg Proscar, daily dosing for up to 4 years reduced serum DHT by roughly 70% [4]. On stopping, the Propecia label states that withdrawal of treatment leads to reversal of effect within 12 months [1].

Do the usual sexual side effects resolve after stopping?

In the 1 mg trials, most did. In three 12-month controlled trials of Propecia in 945 men on drug and 934 on placebo, aged 18 to 41, drug-related decreased libido was reported by 1.8% vs 1.3%, erectile dysfunction by 1.3% vs 0.7%, and ejaculation disorder by 1.2% vs 0.7% [1]. Taken together, 3.8% of treated men reported one or more of these versus 2.1% on placebo (p=0.04), and 1.2% vs 0.9% stopped the drug because of them [1].

The label states that resolution occurred in men who discontinued therapy because of these side effects and in most of those who continued therapy, and that the incidence of each fell to 0.3% or lower by year 5 [1]. A meta-analysis of 15 placebo-controlled trials in 4,495 men with androgenetic alopecia found a 1.57-fold relative risk of sexual dysfunction with 5-alpha reductase inhibitors (95% CI 1.19 to 2.08), and 1.66 (1.20 to 2.30) for finasteride alone [5].

What the label says about symptoms that persist

Beyond the persistent sexual dysfunction wording, the Propecia postmarketing section lists male infertility and/or poor seminal quality, noting that normalization or improvement in seminal quality has been reported after discontinuation [1]. The Medication Guide lists decreased sex drive and ejaculation problems that continued after stopping as possible reported effects [1].

Two caveats sit inside the labels. Postmarketing reports are voluntary, come from a population of uncertain size, and cannot reliably establish a causal relationship [1][4]. For Proscar 5 mg, persistent sexual events were reported rarely, most affected men were older and taking other medicines, and Proscar's independent role is unknown [4]. Neither Propecia nor Proscar has a boxed warning [1][4].

How often does it happen?

The frequency of persistent symptoms is not established. A review of 34 hair-loss trials found that none had adequate safety reporting and 76% evaluated safety for one year or less, with funnel plots suggesting sexual adverse effects were under-detected [6]. So the 3.8% figure describes side effects during year one of treatment, not persistence after stopping.

What studies of former users have found

One series interviewed 71 otherwise healthy men aged 21 to 46 who reported new sexual side effects on finasteride for hair loss that lasted at least 3 months after stopping [3]. Mean finasteride use was 28 months and mean persistence was 40 months at interview; 94% reported low libido, 92% erectile dysfunction, 92% decreased arousal and 69% orgasm problems [3]. The design was post hoc and self-selected with recall bias, so it cannot show how common this is or prove cause [3].

A second study compared 61 former users with persistent sexual side effects against 29 men with hair loss who had never taken finasteride: depressive symptoms on the Beck Depression Inventory II (score of 14 or more) were present in 75% (46 of 61) versus 10% (3 of 29), P<0.0001 [7]. That study was small, self-selected and cross-sectional and cannot prove cause [7].

A third group examined 16 men with post-finasteride symptoms: 8 met criteria for major depressive disorder, all had erectile dysfunction (10 severe, 6 mild to moderate), and those with severe erectile dysfunction had abnormal somatosensory evoked potentials of the pudendal nerve [8]. In that study, researchers reported altered levels of several neuroactive steroids in cerebrospinal fluid and plasma [8].

Depression and suicidal ideation after stopping

The label history matters here. On May 31, 2022, the FDA sent a safety labeling change order citing new information on suicidal ideation and behavior, additional risk of sexual dysfunction and psychoneurocognitive adverse events; the supplement approved August 1, 2022 changed the postmarketing wording to 'depression, suicidal ideation and behavior' [2]. Those remain postmarketing reports [2].

A before-and-after study of 128 men with androgenetic alopecia on finasteride 1 mg/day compared the same men before treatment and two months in. Depression scores rose significantly on both the Beck Depression Inventory (baseline mean 12.11; P<0.001) and the HADS depression scale (P=0.005), while the change in anxiety score was not significant (P=0.061) [10]. There was no placebo group.

Large cohort studies in older men give a mixed picture. In 93,197 Ontario men aged 66 or older starting a 5-alpha reductase inhibitor, mostly for prostate enlargement, suicide was not 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); 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 [11]. In 2,236,876 Swedish men aged 50 to 90, of whom 70,645 started finasteride at a median age of 73, depression was more common (HR 1.61, 1.48 to 1.75) and stayed constant over time, while suicide was not associated (HR 1.22, 0.99 to 1.49) [12]. Neither cohort studied young men taking 1 mg for hair loss.

Is there a taper schedule?

The Propecia label's dosing is one 1 mg tablet once daily and it gives no tapering schedule [1].