The Importance of Esters

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What is an ester?
In the context of injectable AAS an ester is an acid with carbon backbone of a certain length, that is attached to the 17beta-hydroxyl group of the AAS. The general purpose is to make the drug more lipophilic (fat-loving) so that it?s retention in the muscle is prolonged. Once the steroid reaches the bloodstream, the ester is hydrolyzed yielding the pure steroid in the bloodstream. As such an ester doesn’t actually change anything to what the actual steroid does. Pharmacokinetically it only slows the appearance and release into the bloodstream.

A few things to consider with esters

However there are three things to consider about esters and their relevance to AAS.1. The difference in amount of the steroid injected. Usually longer esters, or the use of phenyl rings and double bonds, are more effective at slowing down the rate of appearance in blood. But both, and especially the use of Phenyl rings, increases the weight of the ester. That means when you express the weight of a steroid in solution, in conjunction with its ester, the heavier the ester, the less of the actual steroid it contains. For instance 100 mg/ml is a concentration. It expresses the amount, in weight, of a compound in 1 ml (the volume) of a solution. But the concentration is the concentration of the steroid with ester since they are listed as a single compound. Comparing two esters of the same drug, let?s say testosterone propionate, enanthate and cypionate, they will contain different amounts of actual testosterone once released in blood. They contain respectively 78.8, 67.8 and 65.8% of testosterone. So on a ml per ml basis with the same concentration, you get more testosterone out of Propionate. Of course since the pharmacodynamics of the compounds are different we use different concentrations and frequency of injection that will impact the amount of testosterone we get over a certain amount of time. As I hope to show at the end of this article, people often grossly overestimate the difference in content however. One I have commonly seen is when comparing tren enanthate to tren acetate. Somehow the perception has risen that 350 mg acetate is worth more than 600mg of enanthate. But at 81.1 and 66.2% respectively, you?ll find those doses amount to 284 and 397 mg of trenbolone each. A difference of more than 100mg in favour of enanthate. However enanthate is often used in a different fashion, injected one per half-life (weekly) and will build up slower. Hence stabilized levels are reached faster and stability is maintained easier with more frequent injection. However since many users now realize you can only judge the difference with a time shift of almost a week and a half, and are injecting enanthate bi-weekly to e3d we are actually seeing there isn?t a huge difference between the compounds. When you also compare price-wise that longer esters, at least for underground gear (tren being a good example since its always underground), are typically cheaper, it makes sense, for some compounds, to opt for the longer esters.2. The difference in metabolization rate. AAS metabolize at the hands of a ton of enzymes in the body. The rate of appearance influences the rate of metabolization. The higher the bolus, the higher the degree of metabolization. Orals for instance will metabolize heavily, since they are released in a huge bolus, and go through the liver first. It?s no coincidence that the strongest oral anabolics are also those most often associated with effects mediated by their metabolites, like Methandrostenolone and especially oxymetholone.

Esters and metabolites

But we need to make a key difference between compounds with active metabolites, and those that have only inactive metabolites. For instance trenbolone has very few metabolites, and they are all inactive or less active. Fluoxymesterone has a ton of metabolites, but all of them less active. Testosterone however has tissue specific conversion to potent estrogens and androgens. So the a difference in rate of metabolisations impacts the effect it has on the body in terms of results and side-effects. When you inject testosterone suspension, you tend to blow up, because the bolus dose is heavily metabolized to both estrogen and DHT. It will also spike a steady increase in SHBG production to buffer it. This forms a tremendous base to build growth on, an anabolic environment, but it also drastically increases water retention, blood pressure and incidence of estrogenic side in those people prone to it. Ester testosterones do not have this problems because they slowly build up to a more stable dose, and despite small fluctuations is mostly kept stable throughout. This decrease the rate of metabolisation by spreading the testosterone out over time more. Even if you compare an acetate to a suspension, the acetate spreads the dose over 36-48 hours, where the base will enter blood within the hour. So while you might be inclined to use both on a daily basis, the effect is hugely different. This won’t apply to a huge amount of compounds, but it surely demonstrates that for testosterones, esters are more relevant than for most compounds.3. Build-up and distribution of dose. You can easily compare esters of the same drug, provided you inject them at the same time-point during their half-life, and extrapolate them time-wise. If you inject once every half-life you can use tren acetate every 36 hours and tren enanthate once every 6 days. But in most cases we will use more frequently. This brings up two issues. The first is comparing products injected during different points, like tren acetate daily vs tren enanthate weekly. Obviously build-up will be considerably slower for the enanthate and the peak dose will be roughly around the half-life. With ed injections of acetate you will actually not just build up faster, but the peak dose will be higher than the half-life, because a larger dose of the first injection still remains in you when you place the second. As such you can really only compare equally spaced doses, based on half-life. So tren ace ed would only compare equally to tren enth e3d. The second problem is that because you are looking at a three times longer period, it takes three times longer to build up to the stable dose in this case. For ace that will only be about 5 days, for enth that will obviously be more like 15 days. For a compound like tren I?ve always found that side-effects are more severe during build-up. This could indeed give the impression that enanthate has more sides, because with ace you?d be through the worst of it in 5 days, and with enth that could last up to 2 weeks. That also means if you use equipotent doses like 350mg weekly of acetate and 430mg of enanthate weekly, that you?ll need to run the enanthate 2 weeks longer for the same results. Comparing doses like 350mg ace to 600mg enth however, you should arrive at the same or better results, provided both are run for a sufficient length of time (8+ weeks)

Percentage of steroid in common esters

Testosterone Propionate (78.8%)

Testosterone Phenylpropionate (64.5%)

Testosterone Enanthate (67.8%)

Testosterone Cypionate (65.8%)

Testosterone Undecanoate (59.4%)


Nandrolone Phenylpropionate (63.3%)

Nandrolone Decanoate (60%)


Trenbolone Acetate (81.1%)

Trenbolone Enanthate (66.2%)


Drostanolone Propionate (79.7%)

Drostanolone Enanthate (69%)


Methenolone Acetate (82.9%)

Methenolone Enanthate (68.8%)


Boldenone Undecylenate (59.5%)

Big Cat

Peter Van Mol has an education background in biochemistry and molecular biology. He has been a fitness and physique enthusiast for nearly 15 years now, during which time he has functioned as a personal trainer for many people, including many top level amateur athletes.

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