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Finasteride Sleep Architecture Impact: What the Evidence Actually Shows

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At a glance

  • Drug / finasteride 1 mg (Propecia) for male pattern hair loss; 5 mg (Proscar) for BPH [5][6]
  • Human sleep-stage data / none found
  • Proposed route / fewer 5-alpha-reduced neurosteroids that enhance GABA-A inhibition [1]
  • Brain entry / crosses the blood-brain barrier [3]
  • Serum DHT / about 65% suppressed within 24 hours on a 1 mg tablet [3]
  • Year-1 drug-related events / decreased libido 1.8% vs 1.3%, erectile dysfunction 1.3% vs 0.7%, ejaculation disorder 1.2% vs 0.7% [3]
  • Drug-related somnolence with 5 mg, MTOPS trial / 1.7% finasteride vs 1.5% placebo [7]
  • Boxed warning / none on Propecia or Proscar [3]

Does finasteride change sleep architecture?

The Propecia label lists what the controlled trials assessed: hair count, patient self-assessment, investigator assessment, photographs, sexual function and non-scalp body hair growth [3]. Kaufman and colleagues reported the hair-count results from two 1-year trials in 1,553 men: 107 more hairs than placebo at 1 year and 138 more at 2 years, counted in a 1-inch circle of vertex scalp (P<0.001) [4]. Sleep stages were not an endpoint.

Where the hypothesis comes from

5-alpha reductase does more than convert testosterone to DHT. Both isoforms also reduce progesterone and deoxycorticosterone, and the next step produces neuroactive steroids that enhance GABA-A receptor-mediated inhibition [1]. In pregnant rats given finasteride repeatedly, allopregnanolone fell further in brain than in plasma, and the decreases in GABA-A function and gamma2L subunit mRNA normally seen in pregnancy did not occur [2]. That work involved no sleep recording. Finasteride does cross the blood-brain barrier [3].

What the trials measured

Three 12-month placebo-controlled trials of Propecia (finasteride 1 mg; 945 men on finasteride, 934 on placebo, aged 18 to 41) reported drug-related decreased libido 1.8% vs 1.3%, erectile dysfunction 1.3% vs 0.7% and ejaculation disorder 1.2% vs 0.7%; 3.8% vs 2.1% reported one or more of these (p=0.04) [3].

In a separate Proscar trial in men with BPH (MTOPS, 3,047 men), drug-related somnolence was reported by 1.7% of men taking finasteride 5 mg alone and 1.5% on placebo [7]. That is a somnolence rate, not a measure of sleep architecture.

Psychiatric outcomes, not sleep

The Propecia label lists depression and suicidal ideation and behavior as postmarketing reports rather than a boxed warning, and states those voluntary reports cannot reliably establish causation [3]. Two cohort studies tracked psychiatric diagnoses rather than sleep: 93,197 Ontario men aged 66 or older starting finasteride or dutasteride [9] and 2,236,876 Swedish men, 70,645 of whom started finasteride [10].

Frequently asked questions

Does finasteride cause insomnia?
Insomnia is not among the drug-related events the 12-month Propecia trials reported at 1% or more, which were decreased libido, erectile dysfunction and ejaculation disorder [3]. In the separate Proscar MTOPS trial, drug-related somnolence was 1.7% on finasteride 5 mg vs 1.5% on placebo [7]. Neither result measures sleep quality or sleep stages.
How could finasteride affect sleep at all?
It blocks 5-alpha reductase, the enzyme step that also produces neuroactive steroids enhancing GABA-A inhibition, and it crosses the blood-brain barrier [3][1]. In pregnant rats, finasteride lowered brain allopregnanolone more than plasma allopregnanolone [2].
Does 5 mg affect sleep differently from 1 mg?
DHT suppression is nearly the same at both doses: after 42 days in 249 men, serum DHT fell 71.4% at 1 mg and 72.2% at 5 mg [11]. The only sleep-related trial figure is drug-related somnolence with 5 mg in MTOPS, 1.7% vs 1.5% on placebo [7].
What should I do if my sleep changed after starting finasteride?
The Propecia label directs suspected adverse reactions to be reported to Organon at 1-844-674-3200 or to FDA at 1-800-FDA-1088 or www.fda.gov/medwatch [3].

References

  1. Finn DA, Beadles-Bohling AS, Beckley EH, Ford MM, Gililland KR, Gorin-Meyer RE, et al. A new look at the 5alpha-reductase inhibitor finasteride. CNS Drug Rev. 2006;12(1):53-76. A new look at the 5alpha-reductase inhibitor finasteride
  2. Concas A, Mostallino MC, Porcu P, Follesa P, Barbaccia ML, Trabucchi M, et al. Role of brain allopregnanolone in the plasticity of gamma-aminobutyric acid type A receptor in rat brain during pregnancy and after delivery. Proc Natl Acad Sci U S A. 1998;95(22):13284-9. Role of brain allopregnanolone in the plasticity of gamma-aminobutyric acid type A receptor in rat brain during pregnancy and after delivery
  3. U.S. National Library of Medicine, DailyMed. Propecia (finasteride 1 mg) tablets, Organon prescribing information. Propecia (finasteride 1 mg) tablets, Organon label
  4. Kaufman KD, Olsen EA, Whiting D, Savin R, DeVillez R, Bergfeld W, et al. Finasteride in the treatment of men with androgenetic alopecia. Finasteride Male Pattern Hair Loss Study Group. J Am Acad Dermatol. 1998;39(4 Pt 1):578-89. Finasteride in the treatment of men with androgenetic alopecia. Finasteride Male Pattern Hair Loss Study Group
  5. Drugs@FDA: FDA-Approved Drugs. Drugs@FDA: FDA-Approved Drugs
  6. Drugs@FDA: FDA-Approved Drugs. Drugs@FDA: FDA-Approved Drugs
  7. U.S. National Library of Medicine, DailyMed. Proscar (finasteride 5 mg) tablets, Organon prescribing information. Proscar (finasteride 5 mg) tablets, Organon label
  8. U.S. Food and Drug Administration. U.S. Food and Drug Administration
  9. Welk B, McArthur E, Ordon M, Anderson KK, Hayward J, Dixon S. Association of Suicidality and Depression With 5α-Reductase Inhibitors. JAMA Intern Med. 2017;177(5):683-691. Association of Suicidality and Depression With 5α-Reductase Inhibitors
  10. Garcia-Argibay M, Hiyoshi A, Fall K, Montgomery S. Association of 5α-Reductase Inhibitors With Dementia, Depression, and Suicide. JAMA Netw Open. 2022;5(12):e2248135. Association of 5α-Reductase Inhibitors With Dementia, Depression, and Suicide
  11. Drake L, Hordinsky M, Fiedler V, Swinehart J, Unger WP, Cotterill PC, et al. The effects of finasteride on scalp skin and serum androgen levels in men with androgenetic alopecia. J Am Acad Dermatol. 1999;41(4):550-4. The effects of finasteride on scalp skin and serum androgen levels in men with androgenetic alopecia
Evidence overview for finasteride: Finasteride Sleep Architecture Impact: What the Evidence Actually Shows