Boldenone Undecylenate

**Boldenone undecylenate** is a long-acting, injectable **anabolic steroid** derived from testosterone. It is primarily labeled for use in veterinary medicine to treat debilitated horses, aiding in the improvement of weight, hair coat, and general physical condition. In small animal medicine, it has historically been used off-label as an appetite stimulant in cats, though its use has largely been supplanted by safer and more effective alternatives due to the risk of hepatotoxicity. > **Clinical Pearl:** Boldenone is formulated as an undecylenate ester in a sesame oil vehicle, which delays its absorption from the intramuscular injection site and provides a sustained release over several weeks. Due to its muscle-building properties, it is a **Schedule III (C-III) controlled substance** in the US and carries a high risk for human abuse and diversion.

Mechanism: Boldenone works by binding to intracellular **androgen receptors** in muscle and other tissues → the receptor-steroid complex translocates to the nucleus → alters gene transcription → promotes protein synthesis, nitrogen retention, and tissue building (anabolism) while reversing catabolism. * **Erythropoiesis:** Stimulates red blood cell production, likely by increasing the production of **erythropoietic stimulating factor (erythropoietin)**. * **Endocrine Feedback:** High doses cause negative feedback on the hypothalamus and pituitary gland → inhibits **Luteinizing Hormone (LH)** and **Follicle Stimulating Hormone (FSH)** → suppresses endogenous testosterone release and impedes spermatogenesis. * **Electrolyte Balance:** Causes retention of nitrogen, sodium, potassium, and phosphorus, and decreases urinary excretion of calcium.

VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.