Equipoise is the most commonly recognized trade name for boldenone undecylenate, an injectable veterinary steroid that exhibits strong anabolic and moderately androgenic properties. The undecylenate ester extends the activity of the drug greatly (the undecylenate ester is only one carbon atom longer than decanoate), so that injections need to be repeated only once every 3 or 4 weeks. The well-balanced anabolic and androgenic properties of this drug are greatly appreciated by athletes, who generally consider it to be a stronger, slightly more androgenic, alternative to Deca-Durabolin®. It is generally cheaper, and could replace Deca in most cycles without greatly changing the end result. Boldenone undecylenate is also commonly known as a drug capable of increasing red blood cell production, although there should be no confusion that this is an effect characteristic of nearly all anabolic/androgenic steroids.
Ciba reportedly patented boldenone as a synthetic anabolic steroid in 1949. During the 1950s and the firm developed several experimental esters of the drug, and would later release a long-acting form of the agent (briefly) in the form of boldenone undecylenate. It would be sold under the brand name Parenabol, which likely referred to its characteristics as a parenteral (injectable) anabolic agent. Parenabol saw some clinical use during the late ’60’s and early ’70’s, mainly as a lean-tissue-preserving anabolic agent in cases of wasting, and for the retention of bone mass with osteoporosis. Boldenone undecylenate was a short-lived preparation on human medical markets, however, and would be discontinued globally before the end of the 1970s. Squibb would ultimately be most famous for introducing this agent in the veterinary market and would sell it under its now most famous trade name, Equipoise.
In the veterinary market, boldenone undecylenate is most commonly applied to horses, although in many regions it is indicated for use in other animals as well. It generally exhibits a pronounced effect on lean bodyweight, appetite, and general disposition of the animal. The Equipoise brand was sold under the Squibb label until 1985, when Solvay acquired Squibb’s U.S. animal health business. Equipoise would be sold under the Solvay label for the next several years until Wyeth finally acquired the animal health division of Solvay in 1995. The division was formed into Fort Dodge Animal Health, which continues to market Equipoise in the U.S. and certain markets abroad today. Many other generic and brand name forms of boldenone undecylenate exist in numerous international drug markets, owing to the fact that any patents on boldenone undecylenate have long since expired.
Boldenone undecylenate is widely available in veterinary drug markets. Composition and dosage may vary by country and manufacturer; the majority of products are supplied as multi-dose glass vials containing an oily solution; usually carrying 25 mg/ml or 50 mg/ml of steroid.
Boldenone is a modified form of testosterone. It differs by the introduction of a double bond between carbons 1 and 2, which reduces its relative estrogenicity and androgenicity. Equipoise® contains boldenone modified with the addition of carboxylic acid ester (undecylenate acid) at the 17-beta hydroxyl group. Esterified steroids are less polar than free steroids, and are absorbed more slowly from the area of injection. Once in the bloodstream, the ester is removed to yield free (active) boldenone. Esterified steroids are designed to prolong the window of therapeutic effect following administration, allowing for a less frequent injection schedule compared to injections of free (unesterified) steroid. Boldenone undecylenate is designed to provide a peak release of boldenone within a few days after injection and sustain hormone release for approximately 21-28 days.
It is interesting to note that structurally boldenone and methandrostenolone (Dianabol) are almost identical. In the case of boldenone (as applied here), the compound uses a 17-beta ester (undecylenate) to facilitate administration, while methandrostenolone accomplishes this with the use of a 17-alpha alkyl group. Aside from this, the molecules are the same. Of course, they act quite differently in the body, which goes to show that the 17-methylation affects more than just the oral efficacy of an anabolic/androgenic steroid.
Side Effects (Estrogenic)
Boldenone is aromatized in the body to estradiol (estrogen). Elevated estrogen levels can cause side effects such as increased water retention, body fat gain, and gynecomastia. Boldenone is considered a mildly estrogenic steroid. Aromatization studies suggest that its rate of conversion to estradiol is roughly half that of testosterone.1 The tendency to develop noticeable estrogenic side effects with boldenone should be slightly higher than nandrolone, but much lower than with testosterone. Estrogenic side effects are usually not pronounced unless this drug is taken in doses above 200-400 mg per week. An anti-estrogen such as clomiphene citrate or tamoxifen citrate might be used to help mitigate these side effects, should they become present. One may alternately use an aromatase inhibitor like Arimidex® (anastrozole), although it is considerably more expensive, and may negatively affect blood lipids.
Side Effects (Androgenic)
Although classified as an anabolic steroid, androgenic side effects are still common with this substance, especially with higher doses. This may include bouts of oily skin, acne, and body/facial hair growth. Anabolic/androgenic steroids may also aggravate male pattern hair loss. Women are also warned of the potential virilizing effects of anabolic/androgenic steroids. These may include a deepening of the voice, menstrual irregularities, changes in skin texture, facial hair growth, and clitoral enlargement.
Note that while boldenone does reduce to a more potent androgen (dihydroboldenone) via the 5-alpha reductase enzyme in androgen-responsive target tissues such as the skin, scalp, and prostate, its affinity to do so in the human body is extremely low.2 The relative androgenicity of boldenone is, therefore, not significantly affected by finasteride or dutasteride.
Side Effects (Hepatotoxicity)
Boldenone is not c-17 alpha alkylated, and not known to have hepatotoxic effects. Liver toxicity is unlikely.
Side Effects (Cardiovascular)
Anabolic/androgenic steroids can have deleterious effects on serum cholesterol. This includes a tendency to reduce HDL (good) cholesterol values and increase LDL (bad) cholesterol values, which may shift the HDL to LDL balance in a direction that favors greater risk of arteriosclerosis. The relative impact of an anabolic/androgenic steroid on serum lipids is dependant on the dose, route of administration (oral vs. injectable), type of steroid (aromatizable or non-aromatizable), and level of resistance to hepatic metabolism. Anabolic/androgenic steroids may also adversely affect blood pressure and triglycerides, reduce endothelial relaxation, and support left ventricular hypertrophy, all potentially increasing the risk of cardiovascular disease and myocardial infarction. Boldenone is likely to have a less dramatic impact on cardiovascular risk factors than synthetic oral anabolic steroids. This is due in part to its openness to metabolism by the liver, which allows it to have less effect on the hepatic management of cholesterol. The aromatization of boldenone to estradiol may also help to mitigate the negative effects of androgens on serum lipids.
To help reduce cardiovascular strain it is advised to maintain an active cardiovascular exercise program and minimize the intake of saturated fats, cholesterol, and simple carbohydrates at all times during active AAS administration. Supplementing with fish oils (4 grams per day) and a natural cholesterol/antioxidant formula such as Lipid Stabil or a product with comparable ingredients is also recommended.
Side Effects (Testosterone Suppression)
All anabolic/androgenic steroids, when taken in doses sufficient to promote muscle gain, are expected to suppress endogenous testosterone production. Without the intervention of testosterone-stimulating substances, testosterone levels should return to normal within 1-4 months of drug secession. Note that prolonged hypogonadotrophic hypogonadism can develop secondary to steroid abuse, necessitating medical intervention.
Although it stays active for a much longer time, boldenone undecylenate is injected at least weekly for physique- or performance-enhancing purposes. It is most commonly used at a dosage of 200-400 mg (4-8ml,50 mg version) per week. The dosage schedule can be further divided to reduce the volume of each injection if necessary, perhaps administering the drug two to three times per week. One should also take caution to rotate injection sites regularly, so as to avoid irritation or infection.
Not a rapid mass builder, boldenone undecylenate instead provides a slow but steady gain of strength and quality muscle mass. The positive effects of this drug become most apparent when it is used for longer cycles, usually lasting 8 weeks or more in duration. The muscle gained should also not be the smooth bulk associated with testosterone, but more defined and solid. Since water bloat is not contributing greatly to the diameter of the muscle, more of the visible size gained on a cycle of boldenone undecylenate should be retained after the drug has been discontinued.
Boldenone undecylenate is a very versatile drug and can be combined with a number of other agents depending on the desired result. For mass, it is commonly stacked with an injectable testosterone such as enanthate or cypionate. This should produce strong gains in muscle size and strength, without the same intensity of side effects of using testosterone (at a higher dose) alone. During a cutting phase, muscle hardness and density can be greatly improved when combining boldenone undecylenate with a non-aromatizable steroid such as trenbolone acetate or methenolone enanthate. Oral c-17 alpha-alkylated agents such as fluoxymesterone or stanozolol may also be used but will present some level of hepatotoxicity. For some, even the low buildup of estrogen associated with this compound is enough to relegate its use to bulking cycles only.
When used for physique- or performance-enhancing purposes, women take much lower doses of boldenone undecylenate than men, typically 50-75 mg per week. Women should take caution with the slow-acting characteristics of this preparation, which makes blood levels difficult to control and slow to decline should virilization symptoms become present.
Boldenone undecylenate remains widely available as a veterinary drug product. It is produced mainly in the Americas, consistently at a dosage of 25 mg/mL or 50 mg/mL. A small number of preparations are made at a higher dosage (typically 200 mg/mL), mainly by companies in less regulated markets of Asia where supply is often dictated by black market demand.
- Biosynthesis of Estrogens, Gual C, Morato T, Hayano M, Gut M, and Dorfman R. Endocrinology 71 (1962):920-25.
- Metabolism of boldenone in man: gas chromatographic/mass spectrometric identification of urinary excreted metabolites and determination of excretion rates. Schanzer, Donike. Bol Mass Spec. 21 (1992):3-16.