Finasteride (Propecia)
Also known as: Propecia, Finasterid, Proscar, Fin, Finasteride
Blocks the conversion of testosterone to DHT — effective against androgenetic hair loss, and useless against the DHT derivatives, because those are already past the step it blocks.
Substance family
Which one works depends entirely on the cause. 5-alpha-reductase inhibitors block a conversion; receptor blockers block the receptor; minoxidil acts on the growth cycle regardless of androgens.
Strain profile
Where this substance is most likely to hit — a rough orientation, individually dependent on dose, duration and predisposition.
This substance works against
Dosing & protocols by goal
Rough orientation ranges as reported in harm-reduction literature — not an individual treatment plan. Doses are individual and open-ended; frequency depends on the ester or half-life.
Androgenetic alopecia (approved indication)
MedicalDose
1 mg / day
Frequency
1× daily
Cycle length
Ongoing — the effect ends when the drug does
Suppresses DHTDHTA far more potent androgen the body makes from testosterone — responsible for hair loss and prostate effects. by roughly 65–70%. Visible results take 3–6 months; anyone judging earlier is judging too early.
Prostate enlargement (approved indication)
MedicalDose
5 mg / day
Frequency
1× daily
Cycle length
Ongoing, medically supervised
The higher dose for a different indication. It does not produce better hair results — DHTDHTA far more potent androgen the body makes from testosterone — responsible for hair loss and prostate effects. suppressionsuppressionThe body shutting down its own testosterone production because an external source is present. is already near maximal at 1 mg.
Lower-dose approach
AdvancedDose
0.5 mg / day or 1 mg every other day
Frequency
Daily or alternating
Cycle length
Ongoing
Used to reduce side effects. DHTDHTA far more potent androgen the body makes from testosterone — responsible for hair loss and prostate effects. suppressionsuppressionThe body shutting down its own testosterone production because an external source is present. falls only modestly, since the dose-response curve is flat in this range.
Side effect & countermeasure
Typical problems and what you can do to reduce harm — at a glance. Does not replace medical monitoring.
Problem
No effect against DHT-derived compounds
Countermeasure
This is the point most often misunderstood. Finasteride blocks the conversion of testosterone to DHTDHTA far more potent androgen the body makes from testosterone — responsible for hair loss and prostate effects.. Drostanolone, stanozolol, oxandrolone and methenolone are already DHT derivatives — there is no conversion left to block. Against hair loss driven by those, minoxidil works (DHT-independent) or a topical receptor blocker such as RU58841.
Problem
Sexual side effects: reduced libido, erectile dysfunction
Countermeasure
Reported in a few percent in trials, higher in observational data. If they appear, stopping usually resolves them within weeks. A lower dose is worth trying first, since DHTDHTA far more potent androgen the body makes from testosterone — responsible for hair loss and prostate effects. suppressionsuppressionThe body shutting down its own testosterone production because an external source is present. barely drops.
Problem
Persistent symptoms after stopping (post-finasteride syndrome)
Countermeasure
Contested in the literature but consistently reported: sexual, cognitive and mood symptoms persisting after discontinuation. The mechanism is unclear and the incidence disputed. What is not disputed is that it is described often enough to belong in the decision — particularly for anyone with a history of depression.
Problem
Mood changes and depressive symptoms
Countermeasure
5-alpha-reductase5-alpha-reductaseThe enzyme that converts testosterone into the more potent DHT. also produces neurosteroids such as allopregnanolone, which act on the GABA system. This is the plausible mechanism behind the mood effects. Pre-existing depression is a reason to discuss alternatives with a doctor.
Problem
Distorted PSA readings
Countermeasure
Finasteride roughly halves PSAPSAA prostate marker that androgens can raise — worth a baseline before it is needed.. A value that looks normal may not be — tell any doctor measuring PSA that you take it, otherwise prostate screening becomes unreliable.
Problem
Estradiol rising
Countermeasure
Testosterone that is not converted to DHTDHTA far more potent androgen the body makes from testosterone — responsible for hair loss and prostate effects. remains available for aromatisationaromatisationThe body converting testosterone into estrogen via the aromatase enzyme.. EstradiolEstradiolThe main estrogen — needed in men too, and damaging in both directions when out of range. can rise modestly. Relevant for anyone already managing it.
Overview
Finasteride blocks the enzyme that converts testosterone into dihydrotestosterone. DHT is the androgen responsible for androgenetic hair loss — it binds to receptors in genetically susceptible follicles and progressively miniaturises them.
Reducing DHT slows or halts that process. The approved dose of one milligram suppresses DHT by roughly two thirds, and in trials that translates into stabilised hair in the majority of users and regrowth in a substantial minority.
In the context of this site, one property matters more than the general hair-loss discussion: what finasteride can and cannot do depends entirely on which compound is causing the problem.
Mechanism of Action
Testosterone is converted to DHT by 5-alpha-reductase. DHT binds the androgen receptor far more strongly than testosterone does — several times over — which is why it dominates in tissues sensitive to it: hair follicles, prostate, skin.
Finasteride inhibits the type 2 isoform of that enzyme, which is the one dominant in hair follicles and prostate. Dutasteride blocks both isoforms and suppresses DHT further.
Here is the part that matters for anyone running anabolic compounds. Finasteride works at the conversion step. It reduces how much DHT is made from testosterone.
Drostanolone, stanozolol, oxandrolone and methenolone are not converted into DHT — they are DHT derivatives. They arrive already past the step finasteride blocks. Taking finasteride alongside them changes nothing about the androgenic pressure on the follicle, which is exactly why the hair loss under those compounds continues regardless.
What does work in that situation acts elsewhere: minoxidil, which stimulates follicles through a mechanism unrelated to DHT, or a topical androgen receptor blocker such as RU58841, which occupies the receptor rather than reducing the hormone reaching it.
Typical Context
One milligram daily, indefinitely — the effect lasts as long as the drug is taken, and hair lost after stopping is lost. Results become visible after three to six months, which is worth knowing before concluding it does not work.
Lower doses are used to reduce side effects, and the pharmacology supports it: DHT suppression at half a milligram is only slightly lower than at one, because the dose-response curve flattens early. Anyone experiencing side effects has that option before abandoning the drug entirely.
The side-effect discussion around finasteride is unusually polarised. Trial data shows sexual side effects in a low single-digit percentage, resolving on discontinuation. Observational reports describe higher rates and, in some cases, symptoms persisting after stopping — post-finasteride syndrome. The mechanism is unclear, the incidence is disputed, and the topic is genuinely unresolved. What can be said honestly: it is reported often enough to belong in an informed decision, and a history of depression is a reason to discuss it with a doctor rather than start on a whim.
Side Effects & Risks
- Reduced libido, erectile dysfunction, reduced ejaculate volume
- Mood changes, depressive symptoms
- Persistent symptoms after discontinuation in some reports (post-finasteride syndrome)
- Gynecomastia, rarely
- Modest rise in estradiol
- PSA readings roughly halved, distorting prostate screening
- No effect on hair loss driven by DHT-derived compounds
Blood Work & Monitoring
- PSA — halved by finasteride; the treating doctor needs to know for correct interpretation
- Estradiol (sensitive) — can rise modestly
- Total/free testosterone — usually rises slightly
- DHT — measurable if the effect needs confirming, though rarely necessary
Harm-Reduction Notes
- Useless against drostanolone, stanozolol, oxandrolone and methenolone — those are already DHT derivatives
- For DHT-derivative-driven loss, minoxidil or a topical receptor blocker are the mechanisms that apply
- Allow 3–6 months before judging the effect
- If side effects appear, try a lower dose before stopping entirely — suppression barely drops
- Tell any doctor measuring PSA that you take it
- A history of depression belongs in the decision, given the reported mood effects
- The effect ends when the drug does; hair kept is kept only while taking it
Legal status by region
Regulation differs considerably between jurisdictions and changes over time. This is a rough orientation, not legal advice — check the rules that apply where you are.
| Region | Regulatory status |
|---|---|
| United States | Prescription-only medicineApproved for androgenetic alopecia (1 mg) and prostate enlargement (5 mg). |
| EU / UK | Prescription-only medicine |
| Canada / Australia | Prescription-only medicine |
| Parts of Asia, Latin America & Middle East | Pharmacy availability variesDispensed without prescription in several countries. |
| Competitive sport | Not prohibitedWas on the WADA list as a masking agent until 2009; removed since. |