A Closer Look at Trenbolone - Part 1
by William Llewellyn

Not too many steroids have an air of mystique about them quite like trenbolone. It is one of those agents that you will hear talked up aggressively by some guy in the gym, to later find he has not even tried it himself yet. The bodybuilding literature is full of strong, unusual, and often-inaccurate statements about this drug, and consequently an air of misunderstanding has begun to cloud our view of trenbolone. The unusual history of this compound, including prolonged periods of very limited availability and high selling prices, has no doubt played a part in shaping the view of this steroid in the minds of athletes. It seems when anything is out of reach, overly expensive or both, people start looking at it in a different way. I therefore thought it would be a good idea to take a closer look at the physical properties of trenbolone, as well as its current state of availability and use.


Structurally trenbolone is a derivative of nandrolone, carrying two additional double carbon bonds at positions 9 and 11 (hence the prefix “tren”, short for tri-en). The activity of trenbolone differs from that of its parent hormone considerably however. To begin with, trenbolone cannot aromatize to estrogen. The delta-9 group present on its structure occupies a bond necessary for aromatization of the A-Ring to be possible. Unless this group is removed metabolically, which it does not appear to be, estrogen synthesis is impossible in the body. Although nandrolone is a weak substrate for aromatase, estrogen levels can still rise during use. With trenbolone we actually expect a lowering of serum estrogen levels, as it should suppress endogenous testosterone release (the primary substrate for estradiol in men).

Androgenic Activity

Although derived from nandrolone, trenbolone is comparatively far more androgenic than this steroid. In fact it is several times stronger in this regard than our primary androgen testosterone as well (1). The first contributing factor to this of course is that trenbolone is a strong binder of the androgen receptor. This trait is also characteristic of its parent nandrolone, which is several times more active than testosterone in this regard. Androgen binding is in fact further enhanced by the introduction of double bonds in delta-9,11 (2), which makes trenbolone an even more potent agonist of the androgen receptor than nandrolone. Perhaps more significant though is the fact that unlike nandrolone, the strong receptor binding potency of trenbolone is not diminished in androgen sensitive tissues by 5-alpha reductase. Trenbolone does not seem to undergo 5-alpha reduction in humans to any appreciable degree at all, which is evidenced by the fact that the major urinary metabolites of trenbolone all possess the original tri-en structure with an intact delta-4 group (3). So trenbolone retains its original potency as it enters cells in androgen target tissues with high 5AR concentrations, as this enzyme is not affecting it. These factors work together to allow trenbolone to be a potently androgenic steroid, instead of a primarily anabolic one in nature like nandrolone. .

Progestational Activity

It has been reported in other bodybuilding literature that trenbolone does not exhibit any activity as a progestin in the body. I am not certain where this belief originated, as trenbolone does appear to exhibit the classic progesterone receptor binding ability that is characteristic of nandrolone and its derivatives. One study looking at the bovine uterine progesterone receptor for example found trenbolone to be a very potent binder, startlingly even more so than progesterone itself (4). Another looking at the binding of various compounds to the androgen, estrogen, progestin, mineral corticoid and glucocorticoid receptors found trenbolone to be a more potent binder of the progestin receptor than nandrolone (5), a steroid normally noted for its usual activity in this regard. What does this mean for trenbolone? I don’t think it really means that much. Trenbolone clearly doesn’t cause gyno, water retention or fat buildup, which one might attribute to estrogenic or progestational activity. So whatever slight action it does have as a progestin on paper doesn’t amount to all that much in the real world. The absence of estrogen may be a significant factor, as progesterone is believed to cause gyno by enhancing estrogen’s stimulation of mammary gland growth (6). Perhaps when trenbolone is taken with other aromatizable compounds it could affect a person’s sensitivity level to gyno and water/fat retention. This seems logical, at least in a technical sense, although admittedly I have seen no evidence to support this.

Mass or Cutting Agent

The potently androgenic and non-aromatizing nature of trenbolone makes it an extremely effective hardening and cutting agent. In fact, it is thought of as unmatched in its capacity as a body-sculpting steroid. Many competitive bodybuilders similarly find it indispensable to any good pre-contest cutting stack. For this type of purpose I doubt another steroid would serve you better. Many people do additionally find they make very good muscle gains with trenbolone. It is a potent muscle-builder, although we should probably not consider it an ideal mass-builder when used alone. The absence of estrogen is an important factor, as this trait seems integral in this type of steroid. This probably has to do not only with water retention but also interactions between estrogen and muscle glucose utilization, GH release and androgen receptor proliferation. Today we are finally starting to understand why this hormone is needed for optimal growth. Trenbolone is probably still the most potent muscle-building agent of all the non-estrogenic steroids though, and admittedly is quite unusual in its potency in this regard. But I would still think that if mass were the goal and you were choosing only one steroid, testosterone, Dianabol or Anadrol would be more productive every time in terms of overall size, weight and muscle mass gain.


As mentioned in the opening of this article, trenbolone has been plagued by periods of manufacturing inconsistency, high prices and scarce availability since it first hit the market in the early 80’s. There is probably little need to revisit in detail the rise and fall of Finajet in the 1980’s, or the demise of Parabolan in 1997. Clearly the colorful history of trenbolone is well discussed. But today’s situation is no less interesting, as we are in a unique situation. For the first time in four years we have a legitimate injectable trenbolone again, as the Mexican veterinary drug firm Laboratories Ttokkyo has recently started producing Trenbol, a 10 ml bottle of trenbolone acetate (TA) in the strength of 75mg/ml. This product is not cheap, and usually sells for upwards of $150 a bottle. Reportedly Denkall is working on a similar item, and there are some reliable underground generics floating about as well that sell for a better price and usually supply a comparable amount of TA. There have been some questions about raw material supply lately though, and whether or not both types of product would remain on the market. This discussion was heightened by the recent removal of Trenbol from Ttokkyo’s website, which is making a lot of people nervous that this product may be on the way out. Hopefully this is just a website problem and not a repeat of the fate that fell on Finajet and Parabolan. If these products do dry up, trenbolone will still be available, but in the form of cattle implant pellets. In Part II of this article I will take a closer look at these unusual products, as well as the various methods utilized by bodybuilders in an effort to effectively use them.

The Laws

In 1970, Congress passed the Comprehensive Drug Abuse Prevention and Control Act. Title II of the Act, known as the Controlled Substances Act (CSA), gave the Department of Justice the authority to regulate drugs of abuse. On November 29, 1990 the Anabolic Steroids Control Act was passed, which amended the CSA to include anabolic steroids as schedule III drugs of abuse. The CSA however specifically excludes approved veterinary implant pellets that contain anabolic steroids. Below is an excerpt from the March/April 1999 FDA veterinarian newsletter that explains this issue:

Examples of Schedule III products include androgenic anabolic agents, such as boldenone, testosterone, and stanozolol. Since these drugs are formulated in both injectable and tablet dosage forms and have potential for abuse, they have not been exempted from CSA. Anabolic agents which are used as implants are unlikely to be abused, and therefore are exempted from Schedule III requirements of CSA. An example of these types of drugs is trenbolone acetate which is chemically and pharmacologically related to testosterone and defined as a controlled substance under Title 21, Part 1300.01(a)(4) of the CFR. Since it is only approved as an implant, trenbolone acetate is exempted from CSA requirements.

Although excluded from the controlled substances act, such products could still be regulated as prescription drug items. That however is not the case with trenbolone acetate implant pellets at this time. Noting that they are not controlled substances, have been deemed safe, are not used for diseased conditions and the practice of implanting livestock is well understood by those in the industry, The Center for Veterinary Medicine has recommended over-the-counter (OTC) distribution for trenbolone acetate implant pellets. We must remember however that the CSA removes exempt status from any anabolic steroid implant product that is sold with the intent that they are for human consumption. You will therefore not find trenbolone sold in the back pages of the fitness magazines, at least not from a proprietor that wants to stay out of trouble with the law.

The Pellets

I thought the opening section was necessary to help you understand the actual laws as they stand in the U.S. at this time. Trenbolone, in the form of trenbolone acetate cattle implant pellets, are not controlled substances, and are sold over-the-counter in the United States without federal regulation. Currently the most popular such product is Finaplix®, sold by the now merged Hoechst-Roussel Agri-vet Company. This product comes in two forms, Finaplix-H® and Finaplix-S®, which denotes if the product was intended for a Heifer or a Steer respectively. The total dosages of both products are different, with the “H” cartridge containing 100 20mg TA pellets (2,000 mg) and the “S” version only 70 (1,400 mg). The retail price for the H, the more popular item, is about $40. Ivy Animal Health also recently introduced two competing products of similar makeup, sold as Component-TH® and Component-TS®. Their products come in double-sized cartridges, such that the TH version contains 4,000 mg of TA and sells for around $75.00. Versions of both products containing trenbolone and estradiol are also produced, however are excluded from this discussion as they are of no interest to the athlete.

Using the Pellets

As mentioned in the FDA memo above, trenbolone is considered safe, and is excluded from controlled substance laws, specifically because it comes in a form not useable by humans, at least not directly. Trenbolone is normally an injectable steroid, which makes using these pellets extremely difficult. No one is of course going to use a cattle implant gun to administer them, and they can’t just be taken orally, so we must find a more creative way to use them. The pellets themselves are small, hard and contain a good amount of binders in addition to 20mg of TA. Most methods adopted involve administering both the steroid and binders to the person, which should be safe, as the binders were designed for internal use and are non-toxic. Although this list could be much more expansive, below are a few of the more popular methods utilized by bodybuilders.


The oldest and probably still most popular way to use trenbolone implant pellets is to make them into a transdermal solution with the use of DMSO (dimethyl sulfoxide). DMSO is a natural solvent derived from wood pulp, and is an extremely effective transdermal carrier. It is similarly capable of pulling trenbolone acetate into circulation through the skin. I believe this practice was first suggested by Dan Duchaine many years ago, and is without question an effective way to use this product. To accomplish this, the pellets are simply ground up and added to a solution of 50% DMSO, 50% water (pure DMSO would be too irritating to the skin). It is important to use pharmaceutical (pure) DMSO, and not industrial grade, which will have a good amount of impurity to it. Just enough solution is used to dissolve the desired amount of powder, as this end product is much more a liquid than a gel and runs off the skin easily if too much is applied (alternately a gel form of DMSO could be used). Typically 3 to 4 pellets are used per day, and due to the rapidity in which DMSO penetrates the skin the daily dose is divided into two or three separate applications.

A major drawback to DMSO is that this substance has an extremely pungent odor to it. You can usually pick out someone taking trenbolone this way, as a garlicky odor will most likely be permeating from his person, particularly his breath. There are also other concerns with DMSO, including the fact that it is so effective a solvent and carrier that it pulls just about anything with a small enough molecular weight into the skin with it. Users should be cautious to thoroughly clean the skin before applying, and be cognizant of what comes into contact the area soon after. Some go so far as to use plastic-wrap, which protects both the skin from contaminants and the steroid application from rubbing off. DMSO users also frequently report minor side effects such as itching or burning rashes at the site of administration as well, which make this type of use less than perfectly comfortable for many. Pat Arnold had once made the suggestion of diluting DMSO to about 5-10% with 190 proof grain alcohol (isopropyl would work also). The alcohol acts as a carrier like DMSO, but quickly evaporates after application leaving a film of steroid and DMSO on the skin. For those very sensitive to DMSO, this mixture may allow for a less irritating (or less garlicky) dermal as you can reduce the amount used.

Raw Injection

This is the practice of simply grinding up the pellets and mixing them with an injectable oil-based steroid or vitamin compound. The pellets are typically just crushed with the back of a spoon, and the powder dropped into the open top of a syringe loaded with a low dose steroid such as Equipoise or 50mg Deca. The solution is periodically mixed (shaken) and then left to sit, so that as much powder as possible will dissolve into the solution before it is injected. Often a 21-gauge needle is needed, as the remnant powder might clog a needle of smaller size. Although effective, this process is generally thought of as the dirty way to use trenbolone. There are some clear sterility concerns, and the injection is a mix of steroid and all the pellet binders and glue. For these reasons, many who want to attempt making in injectable opt to purchase one of the commercial “Fina Injection Kits” which produce a cleaner product.

Injectable Kits

A few kits are currently being sold that offer a better way to home-brew an injectable solution from your trenbolone acetate pellets. The processes involved are much more detailed, but result in a sterile solution of 75mg/ml trenbolone acetate, free of binders and contaminants. I spoke with a well-known chemist who identifies himself as Animal, about the kit he had developed. He is very guarded about the actual ingredients, but assured me that the final solution produced by his kit was a sterile oily solution, which included a 10% benzyl alcohol content (a common anti-microbial agent used in injectable drugs). The process he outlined was as such. Crushed pellets are added to an unidentified solution, which acts as a solvent dissolving the powder. Once fully mixed, a measured amount of oil is added to the solution. After sitting for some time, a strong separation will occur such that a clear solution will sit on top of thin opaque layers of liquid (the opaque layer contains the glues and binders). The clear solution (containing the steroid) is…