Exemestane 12.5

Orals

Exemestane 12.5

Exemestane 12.5 is a pharmaceutical tablet formulation of Exemestane at 12.5 milligrams per tablet. Exemestane is a third-generation steroidal aromatase inactivator — also described as a type I aromatase inhibitor or "suicide inhibitor" — approved for the treatment of hormone receptor-positive breast cancer in postmenopausal women. Its mechanism of irreversible aromatase enzyme inactivation distinguishes it pharmacologically from non-steroidal aromatase inhibitors and has important implications for the depth and duration of estrogen suppression it achieves.

Structural Profile and Classification

Exemestane is a steroidal compound structurally related to androstenedione — the natural substrate of aromatase (CYP19A1). This structural similarity allows exemestane to bind to the active site of aromatase with very high affinity. Unlike non-steroidal aromatase inhibitors that bind reversibly to the enzyme's haem iron, exemestane binds covalently and irreversibly to the enzyme active site, forming a stable intermediate that permanently inactivates the enzyme complex. This irreversible inactivation is the pharmacological basis of the "suicide inhibitor" classification — the enzyme is inactivated with each catalytic cycle, and suppression of estrogen biosynthesis persists until de novo enzyme synthesis replaces the inactivated pool.

Pharmacokinetic Profile

Exemestane is rapidly absorbed following oral administration, with peak plasma concentrations at approximately 1.2 hours post-dose. Absolute bioavailability is enhanced by approximately 40% when taken with a fatty meal. The plasma elimination half-life is approximately 24 hours, supporting once-daily dosing. Extensive hepatic metabolism occurs via CYP3A4 and aldoketoreductases, generating the active metabolite 17-hydroexemestane, which retains androgenic activity. Approximately 42% of an oral dose is recovered in urine and 42% in feces as metabolites over one week.

Mechanism of Aromatase Inhibition

Aromatase (CYP19A1) is the enzyme responsible for the rate-limiting aromatization step converting androgens (androstenedione, testosterone) to estrogens (estrone, estradiol) in peripheral tissues. Exemestane acts as a mechanism-based irreversible inhibitor: it enters the aromatase active site as a substrate analogue, undergoes partial CYP19A1-catalyzed processing that generates a reactive intermediate, and this intermediate forms a covalent adduct with the enzyme active site, permanently inactivating the enzyme molecule. Even after exemestane is cleared from plasma, estrogen suppression persists until new aromatase enzyme is synthesized.

Formulation

Each Exemestane 12.5 tablet contains 12.5 mg Exemestane USP as active ingredient, manufactured to USP specification under GMP-compliant conditions. Pharmaceutical excipients include microcrystalline cellulose, crospovidone, hypromellose, and magnesium stearate. Complete release testing including HPLC concentration verification (95–105% of label claim), purity analysis (≥98%), dissolution testing, and microbiological limits evaluation is performed on every production batch prior to release.

Quality Assurance

Every batch of Exemestane 12.5 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 Exemestane 12.5 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.