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Chapter 5

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The structure of testosterone was first synthesized in the mid-1930's. The first anabolic steroid that a scientist first tinkered (and eventually partnered) with an ester is testosterone. The original administration for testosterone (as with other drugs) was through the oral route; but, plain, straight testosterone encounters a problem when going this way. The substance is easily absorbed and most of it is destroyed by the ever-vigilant organ – the liver. This process is known as the first-pass effect or first-pass metabolism, whereby the concentration of a certain drug is significantly reduced before it is systemically circulated. Injectable forms of Testosterone were developed, but the base testosterone must be injected every six to eight hours in order to be effective... So, scientists scramble for a solution. Soon, esterified injectable steroids were born.

What are Esters?

Esters are a class of chemical compounds and moieties. Moieties, more commonly known as functional groups, are specific groups of atoms within the molecules that are responsible for the characteristic chemical reactions of said molecules.

Esters are derived from carboxylic acids thus they are also known as carbonates. The most common kind of ester is probably polyester, a component necessary in many industrial products like clothing, textile, household products and building materials. Carboxylate esters are important components of perfumes and essential oils as they a emit distinctive and a pleasant smell. All natural fats and oils (called triglycerides) and most waxes are mixtures of esters.

There are several ways to synthesize esters and one of the most known processes is esterification. Esterification occurs when a molecule of an acid fuses with a molecule of an alcohol. An ester has two components – alcohol and acid. In ethyl formate (an ester that occurs in lemon and rum), for example, ethyl is the alcohol and formate is the acid part.

Now that you understand some important bits on esters, you can begin your lessons of esters on steroids.

Anabolic-Androgenic Steroids (AAS) and Esters in Sync

Ever came across confusing names on steroid labels like testosterone enanthate, testosterone propionate, or testosterone decanoate? These names mean that the parent hormone is testosterone, the main component of your steroid that is doing all the work in beefing up muscles and allowing you to do Herculean tasks. Of course, this is putting the work of steroids in your body in the most simple of terms, the actual process of the pharmacodynamics and pharmokinetics of steroids is complicated, to say the least.

The second part of the name (the one ending in -ate) is your ester. What is the role of esters on steroids? What do they do? How do they work?

In the case of anabolic/androgen steroids (AAS), esterification occurs when carboxylic acid is attached to the steroid molecule at the 17th beta position. Through this, esters fulfill an important role in the modification of drugs from an oral med to an injectable. Injectable steroids are esterified versions of certain parent drugs.

The Role of Esters in AAS

Esters, are attached on to AAS to affect the release time of the drugs. The Ester makes the steroid oil soluble for injection and keeps it from docking with the Androgen Receptors. This is why some literature calls esters 'time releasing vehicles'. Esters are broken down by enzymes in the bloodstream, thus liberating the steroid compound to do its work.

There are two mail groups of anabolic steroid ester: ling-acting and fast-acting. Long-acting esters slowly break down and take a long time to be cleaved off. Fast-acting esters work the other way – they dissolve rather quickly and free the steroid for action.

As you well know, use of AAS elevates your blood volume (among other important processes). This is because testosterone, whether naturally present or synthetically introduced in your body, increases the red blood cell production. Such increase would mean a viable oxygen and nutrient transport in the body. There is, however, a drawback. If an excessive increase occurs, there is the possibility of platelet aggregation and blood clots.

The problem with steroids is that they have poor solubility with either water or oil. Fat or water solubility is always a concern with many types of drugs including AAS. The esters improve their fat solubility and this enables them to be stored in muscle tissues, which stunts the rate at which the drug can travel from the injection route. Plus, this makes it less prone to being picked out by blood to be circulated throughout the body. Instead, it is slowly but continually being released into the bloodstream.

Basically, the difference between the various esters you see on the labels of steroids is the number of carbon atoms present in esters. A propionate has three carbons while enanthate and decanoate have seven and 10 carbons respectively.

Now how do these numbers affect the pharmacokinetics of drugs? The more cabrons an ester has, the higher its oil solubility is and lower the water solubility becomes. It remains in the injections site longer and deposits in fatty tissue for a while before the ester is cleaved-off and the steroid can exert its intended action. In a way, an ester (specifically its carbon content) makes the steroids hydrophobic, which slows their release into the bloodstream.

Also, the number of carbons affects the partition coefficient, which is the ratio between water and fat solubilities. Higher number of carbons equals higher partition coefficient. And if the partition coefficient is high that translates to a high proportion of drugs that is dissolved in oil or lipid while only a small amount is dissolved in water.

In a nutshell, esters make injection session more convenient for steroid users. They extend the duration of the effects of drugs by slowing the release of the dose given over several days or even weeks in the case of longer ester chains. Keep in mind that aside from slower release times, the esters do not have any effects on the steroid itself. Neither do they improve the anabolic properties of AAS products.

Here are some of the esters attached to steroids to improve their rate of dispersion. You have read many of these names in the description of the most popular steroids being used today.

Esters of Injectable Steroids


This is also known as asetic acid, ethylic acid, vinegar acid, vinegar, methanecarboxylic acid. Acetate esters delay the release of a steroid for only a couple of days. They have an active life of two to three days.

This ester is produced by the reaction of alcohol and acetic acid whereby forming the corresponding alcohol and ester.

This ester is commonly used in the following: oral primobolan tablets (metenolone acetate), Finaplix (trenbolone acetate), testosterone, and trenbolone implant pellets.

Although oral preparations are made from this ester, their effectiveness is debatable.


Propionate slows the release of a steroid for a couple of days. Two to three times per week administrations will prevent blood levels from fluctuating.

This ester has a shorter duration of effect compared to most esters. It has only one to two days of active life, and this is why it is not as popular as cypionate and enanthate.

Many report that testosterone with this ester has several advantages over other testosterone compounds. First, annecdotale evidence suggest water retention is rarely a concern with this one. This can be ideal for bodybuilders who suffer bloating from testosterone enanthate. And because it kicks in after just a few hours, a user experiences a burst of his training energy, better pump, and increased appetite almost immediately.

Testosterone propionate reportedly yields good results for female users since androgenic side effects could be easily avoided with responsible treatment. Having a hormone that is only active for three days, allows female users to discontinue use quickly at the first sign of masculizing effects, while other esters would take weeks to leave the system. Some advise that increasing the time interval between injection schedules can lower the risk of adverse reactions. A longer gap can level off testosterone and that way there won't be accumulation of androgens. Female users are advised to take propionate only every five to seven days and usual dosage is 25-50mg/injection. Duration of treatment should not exceed 10 weeks.

Males, of course, can have a daily 50-100mg injection. Users who are convinced that a daily injection of steroids is what works for them should opt for propionate. Most prefer an initial dosage of 50-100mg. Some of those who are eager to see things going pronto inject 250 mg of test enanthate with 50 mg of propionate at the beginning of treatment. After two days, when the effect of propionate wanes another 50mg is administered. By the fourth day, the enanthate kicks in and propionate injection may not be necessary.


This is referred to as propionic acid phenyl ester. Testoronoe phenylpropionate, used to be called Tstolent, givies you 4-5 days of active life. Its release time falls in the middle of Propionate and Cypionate, since it delays the release a few days longer than a propionate but a few days shorter than cypionate. Injections twice a week (every third or fourth day) would maintain your blood levels steady.

This ester is commonly attached to nandrolone-based compounds such as Deca Durabolin. Sometimes phenylpropionate is also used in testosterone in brand names like Sustanon and Omnadren.


Also referred to as isocaproic acid, isohexanoate, and 4-methylvaleric acid, this ester is close to enanthate in terms of release. It is used in Sustanon and Omnadren, which are considered as 'blends' or multi-esterified steroids. Aratest is also an example of a multi-sterified steroid.

Blends mean that they are released at different times; therefore, there they don't require a bi-weekly schedule. This way, ideal and stable blood levels can be potentially maintained as has been reported by anecdotal evidence.


This ester is referred to as hexanoic acid, hexanoate, n-caproic acid, n-hexoic acid, butylacetic acid, pentiformic acid, n-hexylic acid, 1-pentanecarboxylic acid, hexoic acid, 1-hexanoic acid, hexylic acid and caproic acid.

This ester is almost similar to isocarpoate (identical atom weight and count), thus duration would be similar to isocarpoate with levels maintained for about a week.


These names also refer to this ester: heptanoic acid, enanthic acid, enanthylic acid, heptylic acid, heptoic acid, oenanthylic acid, and oenanthic acid. Enanthate is one of the most popular esters used in steroids. This ester is usually attached to testosterone but is also used in other compounds such as Primobolan Depot. It releases steady but uneven levels of hormone for about 10-14 days. Its typical application in therapeutic treatments is on a bi-weekly or monthly basis. Athletes, however, need at least a weekly schedule to maintain a uniform blood level.


Also referred to as cyclopentylpropionic acid and cyclopentylpropionate, whose release time is similar to enanthate (10-14 days). The difference between these two esters is that enanthate is smaller than cypionate.


Decanoate is commonly used with the hormone nandrolone (Deca Durabolin). Considered to be the heaviest of esters as its release duration extends to as long as four weeks. But athletes do administer a weekly injection because users notice a drop in their levels after two weeks.

This ester is also referred to as decanoic acid, capric acid, caprinic acid, decylic acid, and nonanecarboxylic acid.


This ester has one carbon atom more than decanoate. Thus, its release duration is almost similar to deca (around 3-4 weeks). Undecylenate is indicated for veterinary purposes only (Equipoise) but it does offer benefits to athletes. Weekly injection is again the usual practice amongst athletes.

This substance is also referred to as undecylenic acid, hendecenoic acid, and undecenoic acid.


Undecanoate is also referred to as undecanoic acid, 1-decanecarboxylic acid, hendecanoic acid, and undecylic acid.

Undecanoate is an uncommon ester, found only in the Dynabolan (nandrolone) and Andriol (an oral testosterone undecanoate). Chemically, this ester shares similarities with undecyclenate and likewise has a release time of about 3-4 weeks. There have been reports that Andriol is not very good in delivering testosterone, and this kind of drives home the point that esterified androgens are ideal primarily through the injectable route.


Also referred to as dodecanoic acid, laurostearic acid, duodecylic acid, 1-undecanecarboxylic acid, and dodecoic acid.

Considered to be the longest-releasing ester in manufactured steroids. With well over a month of active life, this ester is found in veterinary nandrolone preparation Laurabolin. Athletes using this report that a remarkable drop in hormone level can occur on the third week.

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Lev Butlerov holds a Masters Degree in Biology, he is NASM Certified, ISSA Certified, The National Council on Strength & Fitness (NCSF) certified and is currently working on his American Council on Exercise (ACE) certificate. From Lev: I love bodybuilding and the biology, chemistry of the industry. It's my hobby and my love. I have done multiple bodybuilding shows, 2 in Germany in the past 5 years. I hope everyone enjoys my articles. In 2021 (going into 2022, 2023) I will be working on my PhD thesis in physiotherapy and biochemistry, I hope to have some of the bits published here.

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