Masteron Propionate (Drostanolone Propionate)
Drostanolone Propionate · Mast P
Drostanolone propionate, marketed historically as Masteron, is an injectable anabolic-androgenic steroid derived from dihydrotestosterone (DHT). It was originally developed in the 1950s and used medically from the early 1960s for treatment of advanced breast cancer in women, based on its mild anti-estrogenic and anti-aromatase properties. The propionate ester is short, with a plasma half-life of approximately 2-3 days, requiring injections every other day or every third day for stable blood levels.
Inject EOD given the 2-3 day half-life. Always pair with a testosterone base. Excellent syringe compatibility with other oil-based AAS - can be combined with test propionate, trenbolone acetate, or NPP in the same injection for reduced pin count.
Start here. Every protocol below is ordered lowest-first. Begin at the smallest effective dose, hold about a week to assess tolerance, and step up only if needed.
How it works
Drostanolone binds the androgen receptor (AR) with moderate affinity and drives protein synthesis and nitrogen retention, with a strong preference for lean tissue. As a DHT derivative, it does not aromatize to estrogen and has no intrinsic estrogenic activity.
A distinctive feature of drostanolone is its mild aromatase-inhibition effect - it competes at the aromatase enzyme with other aromatizable androgens (testosterone, methandrostenolone), reducing estrogen conversion from those compounds. This is why it is often added to a testosterone cycle as a mild AI alternative. It also displaces testosterone from sex-hormone binding globulin (SHBG), raising free testosterone.
Unlike 17-alpha-alkylated orals, drostanolone is injectable and not hepatotoxic in the classical sense. It still suppresses endogenous testosterone production via HPT-axis feedback, though less aggressively than 19-nor compounds. A testosterone base is standard.
What to expect
First 1-2 weeks: subtle drying effect and mild strength improvement. Libido often improves (free testosterone rise from SHBG displacement).
Weeks 3-5: peak hardness and conditioning effect visible, especially in sub-10% body fat. Vascularity noticeably increases.
Weeks 6-10: sustained gains, diminishing return beyond 10 weeks. Side-effect burden mostly androgenic (skin, hair). Cycle off to reset.
Evidence
References for this compound are being re-checked against their source records. We are not showing them until each one is confirmed to support the claim it sits under.
Side effects & safety
Commonly reported
- Accelerated hair loss in genetically predisposed users
- Oily skin and acne (androgenic effect)
- Suppression of endogenous testosterone (dose-dependent)
- Lipid shift (HDL drop, LDL rise)
- Injection site discomfort (short ester, frequent injections)
Less common & notes
- Increased aggression or libido, mood changes, elevated blood pressure, minor cardiovascular markers.
- Women: significant virilization risk at any meaningful dose - generally contraindicated in women except for historical breast cancer use under strict medical supervision.
- Rare: severe lipid shifts, cardiac strain with prolonged high-dose cycling, psychological effects.
Pharmacokinetics
Post-injection
IM (oil depot)
Per injection - supports EOD or E3D dosing
Hepatic metabolism. Renal excretion of metabolites.
Storage. Store at controlled room temperature (20-25°C / 68-77°F). Protect from light. Oil-based solution - do not refrigerate or freeze. Draw with a larger gauge needle and inject with a smaller one (18G draw, 23-25G inject). Keep out of reach of children and in a locked location - Schedule III controlled substance in the United States.
Regulatory status
Schedule III controlled substance in the United States under the Anabolic Steroids Control Act of 1990. Originally FDA-approved (brand name Masteron, Syntex) for advanced breast cancer in women - discontinued in the late 1990s. Possession or distribution without a valid prescription is a federal offense in the United States. Classified similarly in most international jurisdictions.
Put it to work
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The guide & community
The complete Masteron Propionate (Drostanolone Propionate) walkthrough, real protocol discussion and coaching live inside the BlessUp community on Skool.
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