Proviron 25

Orals

Proviron 25

Proviron 25 is a pharmaceutical tablet formulation of Mesterolone at 25 milligrams per tablet. Mesterolone — marketed under the original trade name Proviron since 1967 — is an orally active androgen and anabolic steroid derived from dihydrotestosterone (DHT) that occupies a unique pharmacological niche: unlike most oral anabolic steroids, it is not 17-alpha alkylated, which produces a distinctive safety profile, a predominantly androgenic mechanism, and a primary clinical application in male hypogonadism and male infertility.

Structural Profile

Mesterolone is a 1-methyl, 17-beta hydroxy derivative of DHT. The 1-methyl substitution confers partial resistance to the 3-alpha hydroxysteroid dehydrogenase enzyme in muscle tissue, providing oral bioavailability without recourse to 17-alpha alkylation. This absence of the 17-alpha methyl group means mesterolone is essentially non-hepatotoxic at therapeutic doses, distinguishing it from the broader class of oral anabolic steroids. As a DHT derivative, mesterolone cannot be aromatized to estrogen and acts as a weak peripheral aromatase inhibitor.

Pharmacokinetic Profile

The oral bioavailability of mesterolone is moderate, approximately 3–5% for systemic androgenic activity following hepatic first-pass processing. Despite low systemic bioavailability, the compound is active at androgenic target tissues due to high androgen receptor affinity. Peak plasma concentrations occur within 1–3 hours post-dose, with a plasma half-life of approximately 12 hours allowing twice-daily administration. The compound is extensively hepatically metabolized, with primary metabolites including 1-alpha methyl-3-alpha-5-alpha-androstanediol glucuronide.

Mechanism of Action

Mesterolone exerts its pharmacological effects through three principal mechanisms. First, it binds sex hormone-binding globulin (SHBG) with very high affinity — higher than testosterone or DHT — displacing endogenous testosterone from SHBG and dramatically increasing the free testosterone fraction available for androgenic and anabolic activity. Second, it acts as a weak peripheral aromatase inhibitor, reducing conversion of endogenous and exogenous testosterone to estradiol. Third, it directly activates androgen receptors in androgenic target tissues, providing supplemental androgenic tone during suppressed cycles.

Formulation

Each Proviron 25 tablet contains 25 mg Mesterolone BP as active ingredient, manufactured to British Pharmacopoeia specification under GMP-compliant conditions. The non-17-alkylated structure allows a simpler excipient matrix — microcrystalline cellulose, lactose monohydrate, crospovidone, and magnesium stearate. Complete batch release testing including HPLC concentration and purity analysis, dissolution profiling, and microbiological limits testing is performed prior to distribution.

Quality Assurance

Every batch of Proviron 25 produced by Biomedica undergoes the complete pharmaceutical release testing protocol before distribution. This includes HPLC compound identity confirmation and purity analysis (specification: ≥98%), concentration verification (specification: ±5% of label claim), sterility testing per USP <71>, bacterial endotoxin quantification by LAL assay (specification: <0.25 EU/mL), and particulate matter inspection per USP <788>. A Certificate of Analysis is issued for every production lot.

Authentication

Each unit of Proviron 25 carries a unique authentication code on its outer packaging. This code can be verified instantly on our Authentication page to confirm the product is genuine Biomedica stock.