Veterinary Pharmacology Database
FDA-CVM Boldenone Undecylenate veterinary label (Equipoise)
FDA Center for Veterinary Medicine
EmergingResearch compound
Equipoise (Boldenone Undecylenate)
Boldenone Undecylenate (Δ1-testosterone Undecylenate), veterinary-only injectable AAS. Originally Squibb 1949 human Rx, today exclusively veterinary (horses) – Fort Dodge Equipoise 1972-2008. Slow, stable lean gains; AROMATIZES at ~half the rate of testosterone. "Appetite-stimulant" reputation.
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WHAT IS EQUIPOISE (BOLDENONE UNDECYLENATE)?
Detailed overview
Equipoise (Boldenone Undecylenate) is a Δ1-testosterone Undecylenate-esterified injectable AAS. Originally synthesized by Squibb (USA) in 1949 as Parenabol (human Rx) for elderly male osteoporosis + cachexia treatment, BUT discontinued in the 1970s due to preference for Test esters. In 1972 Fort Dodge Animal Health acquired the license and marketed it as Equipoise veterinary-only (horse joint recovery + appetite stimulant) Rx – also discontinued in 2008. Today UGL market only. Anabolic:androgenic ratio 100:50 (moderate anabolic, moderate androgenic). NOT 17α-alkylated → LOW hepatotoxicity. AROMATIZES (about half as strongly as testosterone, CYP19 substrate). Undecylenate ester (10-carbon undecylenic acid) → long half-life ~14 days, monthly-injection-compatible depot. Classic "slow lean gainer" – 3-5 kg dry muscle in 8-12 weeks + documented appetite-stimulant effect (boldenone-driven). WADA-banned year-round.
Mechanism
AR agonist, Δ1-testosterone, AROMATIZES at half-Test rate
Anabolic:Androgenic
100:50
Half-life
14 days (Undecylenate ester)
Onset
48-72 h (IM)
Legal status
Veterinary-only Rx (discontinued 2008), today UGL; Schedule III
Data console
Lab data
/lab/molecular-data.jsonLIVE
> Androgenic:Anabolic100:50
> AR bindingModerate AR affinity (~50-60% vs testosterone in vitro).
> Active half-life~24 h free boldenone (after hydrolysis)
> Detection windowBoldenone metabolites (1-androstene-3,17-dione + Δ1-androstene metabolite family) urinary 5-6 months (due to Undecylenate slow clearance; WADA-accredited GC-MS/LC-MS/MS, Schänzer 1996 PMID 8616181).
> AromatizationYes – Δ1-testosterone CYP19 substrate at ~50% of Test level; clinically E2 elevation moderate (Pope-Kanayama 2014 PMID 24423981)
> HepatotoxicityLow – parent steroid, NOT 17α-alkylated; IM bypasses first-pass. ALT/AST <2x normal for Equipoise-only cycle (Hartgens-Kuipers 2004 PMID 15233599)
Safety
Side effects, stop signs, contraindications
Side effects · 8
- Polycythemia (abnormally high red blood cell count, hematocrit): boldenone is strongly erythropoietic and can push hematocrit above 54%, raising the risk of thrombosis, stroke and heart attack. This is one of the most clinically significant signature effects of the compound; monitoring and phlebotomy may be required.
- HPTA suppression and reduced fertility: boldenone suppresses the hypothalamic-pituitary-gonadal axis, lowering LH/FSH, causing endogenous testosterone shutdown, testicular atrophy, reduced sperm count and reversible (sometimes lasting) infertility. Recovery requires PCT, started 3-4 weeks after the last injection due to the long ester.
- Adverse lipid profile and cardiovascular strain: decreased HDL ("good" cholesterol) and raised LDL, which together with rising hematocrit and possible blood-pressure elevation increases the risk of atherosclerosis and cardiovascular events with longer or repeated cycles.
- Estrogenic effects from aromatization: boldenone converts to estradiol via CYP19 (about half as strongly as testosterone), which can cause gynecomastia (male breast tissue growth), water retention and elevated estradiol. The risk is lower than with testosterone but not zero; at higher doses an aromatase inhibitor may be needed.
- Androgenic side effects: acne (especially on the back and shoulders), oilier skin, temporal hair thinning in genetically predisposed individuals, and increased libido or irritability. Although boldenone converts to DHT more weakly than testosterone, androgenic effects can appear from moderate doses.
- Virilization in women: voice deepening, increased body hair growth, clitoral enlargement, menstrual disturbances and acne. Some virilizing signs (voice change, clitoral growth) can be permanent or irreversible, making this compound high-risk for women.
- Injection-site reactions (injectable depot): pain, swelling, redness or a lump at the injection site (post-injection pain, PIP), plus risk of sterile or infectious abscess with improper, non-sterile technique. The viscosity of the oily undecylenate ester can increase local irritation.
- Psychological and behavioral effects: mood swings, increased aggression or irritability, and risk of developing AAS dependence with repeated cycles; the post-cycle hypogonadal state can cause depressive symptoms.
Contraindications · 7
- Pre-existing polycythemia / high hematocrit (>54%): absolute contraindication. The strong erythropoietic effect of Equipoise further raises red cell mass, creating life-threatening risk of thrombosis, stroke or heart attack.
- Pregnancy and breastfeeding: contraindicated due to fetal virilization and teratogenic risk. The compound can pass into breast milk and cause irreversible developmental harm.
- Hormone-sensitive cancers: prostate cancer or known/suspected breast cancer (including in men). Androgenic stimulation can accelerate progression of these tumors, so use is prohibited.
- Cardiovascular disease or high risk: existing coronary artery disease, uncontrolled hypertension, prior thrombotic event or severe dyslipidemia. The combination of HDL decline, rising hematocrit and blood-pressure elevation compounds the risk.
- Competitive (WADA / drug-tested) athletes: banned year-round (S1.1.a), and boldenone metabolites remain detectable in urine for 5-6 months due to the long undecylenate ester. Use results in a career-ending anti-doping violation.
- Anticoagulant therapy (e.g. warfarin): boldenone can potentiate the effect of blood thinners, creating a bleeding risk; contraindicated without close INR monitoring.
- Adolescents and youths with incomplete bone growth: androgens can prematurely close the epiphyseal growth plates, irreversibly stunting final adult height.
Related Performance Compounds
Same therapeutic category
Studies
Related research and clinical findings
Endocr Rev. 2014;35(3):341-75.
Adverse health consequences of performance-enhancing drugs: an Endocrine Society scientific statement
Pope HG Jr, Wood RI, Rogol A, Nyberg F, Bowers L, Bhasin S.
PMID: 24423981Open
Sports Med. 2004;34(8):513-554.
Effects of androgenic-anabolic steroids in athletes
Hartgens F, Kuipers H.
PMID: 15248788Open
Clin Chem. 1996;42(7):1001-20.
Metabolism of anabolic androgenic steroids
Schänzer W.
PMID: 8674183Open
Addiction. 2009;104(12):1966-78.
Anabolic-androgenic steroid dependence: an emerging disorder
Kanayama G, Brower KJ, Wood RI, Hudson JI, Pope HG Jr.
PMID: 19922565Open
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MolekulaX Editorial Team·Source-verified · PubMed · FDA · EMA
Updated: June 19, 2026
The information here is for educational and scientific purposes only. Performance-enhancing compounds (AAS, prohormones, stimulants, doping agents) are illegal without prescription in Hungary and most of the EU, and carry serious health and legal risks. WADA bans them in competitive sport. This is NOT a usage guide, and we do not encourage any illegal use. If you do use them, medical supervision and regular bloodwork are ESSENTIAL. Severe endocrine, cardiovascular, hepatic and psychiatric side effects are possible.