Finasteride
5-AR Inhibitor
Also known as Propecia
Half-life
~6-8 hours
What is Finasteride?
5-alpha reductase inhibitor. Prevents testosterone conversion to DHT. Used for hair loss and BPH.
How Finasteride works
Selective type II 5-alpha-reductase inhibition lowers DHT in scalp/prostate tissues.
Benefits & uses
Common uses: Male pattern baldness prevention, BPH treatment, scalp DHT reduction.
Finasteride dosage
Protokol doesn't recommend doses for prescription or controlled compounds. Any figures below are reference or observational reports — dosing should be set with a qualified clinician.
- Reference range
- Literature reports ~1 mg daily (hair) / ~5 mg (BPH)Clinical or reference range, not a personal recommendation.
Finasteride half-life
~6-8 hours (tissue effect longer)
Finasteride side effects
Post-finasteride syndrome (sexual dysfunction, depression) — serious concern for some users.
- Sexual dysfunction
- Mood changes in susceptible users
- Persistent side effects reported rarely
- Sexual side effects (libido/erectile) in a minority
- Mood changes
- Rare persistent effects ('post-finasteride syndrome')
Warnings & monitoring
- Prescription medication — requires a doctor. Not for use by/around women who are or may become pregnant (birth-defect risk). Lowers PSA — tell your doctor.
Monitoring: Watch for sexual/mood side effects; note it lowers PSA readings.
Finasteride interactions
with Dutasteride
Avoid · moderateBoth block 5-alpha reductase. Combining intensifies sexual side effects and the rare risk of post-finasteride-syndrome without meaningful additional DHT reduction.
Timing: Do not combine 5-AR inhibitors
with Testosterone
Caution · moderateFinasteride blocks 5-alpha reductase, reducing DHT conversion from testosterone. May blunt some androgenic benefits on TRT. Linked to persistent sexual side effects in a subset of users (Post-Finasteride Syndrome).
Timing: Finasteride taken daily; discuss risks with prescribing physician
with Testosterone
CompatibleFinasteride (5α-reductase inhibitor) blocks conversion of testosterone to DHT, reducing scalp hair loss and prostate enlargement. Trade-off: reduced DHT means less libido and strength benefit — used selectively.
Timing: Daily finasteride alongside testosterone; standard for TRT patients
Track Finasteride in Protokol.
Log doses, model half-lives, check interactions, and line it all up against your bloodwork. Free on iPhone and Android.
