Anabolic Steroids/Hormones Human clinical data

Masteron Propionate

Drostanolone Prop · Mast P

2 days

Half-life

50–150 mg

Typical dose

EOD

Frequency

6–10 weeks

Cycle length

DHT-derived drostanolone propionate; anti-estrogenic, cutting agent. Simple model — peak calibrated.

Key takeaways

Injectable DHT derivative (drostanolone propionate), formerly the breast-cancer drug Drolban.
~2-day half-life; every-other-day injection keeps serum levels flat.
Cannot aromatize and mildly anti-estrogenic; used for hardening, not mass.
Androgenic sides only (hair, skin, prostate); not hepatotoxic.

Overview

What it is

Masteron (drostanolone propionate) is an injectable DHT derivative carrying a short propionate ester, originally marketed as Drolban for advanced breast cancer before tamoxifen displaced it. It can't aromatize and mildly antagonizes estrogenic signaling, which is why it's treated as an anti-estrogenic hardening agent rather than a mass builder.

Pharmacokinetics

The ~2-day half-life drives every-other-day injection to keep serum levels flat. Bioavailability sits around 84%, and peaks rise and fade fast enough that missed injections show up directly in blood levels.

Harm reduction

Not hepatotoxic, and free of estrogenic effects; the sides are androgenic (hair loss, acne, prostate in susceptible users). HPTA suppression is dose- and duration-dependent, and reported protocols almost always stack it with testosterone rather than run it alone.

Reported dosing protocols

Protocols reported in research literature and clinic/community use — informational context, not a dosing recommendation.

Use case	Dose	Route	Frequency	Duration
Breast cancer (historical label)	100 mg	IM	3× weekly	Months
Cutting (community)	300–400 mg weekly	IM	EOD (50–100 mg per shot)	6–10 weeks

Pharmacokinetic summary

Model tier: Simple (t½ + F, Tmax estimated)
Half-life: 2 days
Cmax: 71.3 ng/dL
Bioavailability: 84%
Typical dose: 50–150 mg

Harm reduction

Aromatizes: No
DHT derivative: Yes
Injection frequency: EOD

Frequently asked questions

Does Masteron block estrogen?

Partially. Drostanolone can't aromatize, and it competes weakly at aromatase and the estrogen receptor, producing a mild anti-estrogenic effect. It won't manage estradiol from a heavy testosterone dose the way an aromatase inhibitor would.

Why is Masteron injected every other day?

The propionate ester's ~2-day half-life means levels drop sharply by day three. Every-other-day injection keeps the curve tight; the enanthate ester exists for people who want twice-weekly dosing instead.

Can Masteron be run alone?

Reported protocols almost always pair it with testosterone, because it suppresses the HPTA without providing any estrogenic activity. Running it solo risks the low-estradiol symptoms (joints, libido, mood) that come with suppressed testosterone and no aromatization.

References

Wikipedia (Llewellyn 2011) — Cmax calibrated to ng/dL serum peak.
Drostanolone propionate overview (Wikipedia, citing Llewellyn 2011) — History and pharmacology summary; the underlying human data is from its breast-cancer era.