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Contested evidence

Finasteride / 5-ARIs

5-alpha-reductase inhibitor·Medication side-effects
⚠ Critical

Post-finasteride syndrome (PFS): persistent sexual, cognitive and mood symptoms after stopping, contested and mechanistically unresolved. Counsel and document consent, especially for cosmetic use in young men.

Effect across the cycle

DesireInhibitory: Decreased libido during use; may persist in PFS.
ArousalInhibitory: Reduced arousal and penile sensation.
PerformanceInhibitory: Erectile dysfunction; possible cavernosal changes.
ClimaxInhibitory: Reduced ejaculate volume.
ExperienceInhibitory: Anhedonia and emotional blunting in PFS.
MemoryInhibitory: Brain fog and cognitive complaints in PFS.

Mechanism

Blocks conversion of testosterone to DHT and reduces neuroactive steroids such as allopregnanolone (5-alpha-reductase is rate-limiting for neurosteroid synthesis). During use: decreased libido, erectile dysfunction, reduced ejaculate volume and penile sensation. A subset develops persistent post-finasteride syndrome (PFS).

Pharmacokinetics
Lipophilic agents cross the blood-brain barrier.
Reversibility
Mostly reversible; PFS is persistent in an affected subset.

Sex differences & notes

PFS includes sexual, neuropsychiatric (depression, brain fog, anhedonia) and physical symptoms after discontinuation.

Key sources

  • Int J Impot Res 2023; PMC7231981