Esterification for Injection


So other than oral administration, you have a few other options, and the most popular is of course intramuscular injection. Nearly all of the injectable steroid compounds use some form of ester to increase their individual half-life within the body. Esterification is a process where a carboxylic acid (a fatty acid) is attached to the actual steroid molecule at the 17th beta position, as apposed to the 17 alpha position of the oral alkylation process. Why do this? Well essentially, what is happening here is the protection of the actual active 17-hydroxyl group. This group is the prime target of steroid metabolism, and with the presence of this ester, the process is in fact prevented. With the addition of the ester, the steroid actually becomes more oil soluble and far less water soluble. Generally the larger the ester chain, then the more oil soluble the steroid compound will be. The more oil soluble the steroid compound, then the harder it is to be absorbed directly into the blood stream, slowing the rate of pick up and circulation, slowing the rate the drug can leave the injection site. And as a result, an inactive deposit (the depot remains inactive while the ester remains present) of a certain steroid can actually sit at the site of injection, being very slowly released and absorbed by the blood, for days or even weeks. What happens when the steroid compound is actually absorbed into the blood stream is that in this free state, the ester is very quickly removed by enzymes, and the base steroid is now rendered active.


Now, when discussing the half-life of injectable compounds you really do have two ways of looking at the subject. Firstly, you may consider that the half life of the drug is the amount of time before release from the injection site into the blood stream in an active state. With most commercial steroid preparations then this time is usually measured in days. When we talk about the actual total active lifespan of most of the esterified steroid preparations, we are really looking at weeks. Your second option when it comes to half-life of an injectable esterified steroid compound, is that of it's half-life in open blood circulation. You may be interested in this figure purely out of personal interest, as it is a very fascinating topic, although the only practical use is that of the relevant measure of the drugs 'release' half-life, when constructing your dosing schedule.


When we look at some research we can see some fairly accurate measurements on both readings. Lets look at some of the human studies on Nandrolone Decanoate, more popularly known as Deca. Deca actually exhibits a mean half life of 6 days for the actual release of the steroid from the injection site into your blood stream. Therefore, when using the above penny experiment, you can get it very clear in your mind, as to why and how Deca remains active within your system for upto a month after your last injection. Next we find that for the hydrolysis of serum nandrolone decanoate to free nandralone is around 4 hours, including total distribution and metabolism of nandrolone. So the actual removal of the ester itself took about an hour or less. Have a look at the following table to see the relative half lives of nandrolone and two other esters of it from intramuscular injection depot. These figures have a great bearing of course on maintaining stable blood serum levels of free drug compound within your system.


Compound Half-Life
Nandrolone 30-40 minutes
Nandrolone phenylpropionate 1 day
Nandrolone decanoate 6 days
Nandrolone laurate 10 Days


It is worth a note that changing the ester used in the suspension will of course alter the release factor into the blood stream. Water based injectable, such as winstrol, are required to be injected far more frequently and are less practical than an esterified steroid compound. This is much more comfortable for the patient or user. You must remember, however, that when calculating doses, the ester is actually figured into the steroids measured weight. So 100mg of testosterone enanthate actually contains much less base hormone than 100mg of straight testosterone suspension. It is possible in some cases that an ester in a compound may make upto and account for roughly 40% or more of the total steroid weight. Typically though the ester will measure somewhere around 20 - 30%.


Unlike with the alpha alkylation at the 17th position, with oral application, esterification of a steroid does not actually affect or alter the activity of the parent steroid. Esters do not alter the property of the steroid. There is no difference between testosterone proprionate and testosterone enanthate, other than the half life of the drugs release time into the blood stream. Your muscles androgen receptor sites only see testosterone.


Faster releasing testosterone esters will produce a faster and greater buildup of estrogen, simply because there is more testosterone in the blood stream from the very start of the cycle.


It is of interest to note that typically the ester is hydrolyzed as stated above, whilst in circulation, via enzymes in the blood stream. However, with injectable depots, a considerable amount of the steroid depot will be hydrolyzed at the very site of the injection upon first contact with the blood. Now this will indeed create a higher concentration of both ester and free testosterone in the actual muscle where the drug was administered. This may potentially equate to better growth in the particular muscle in question, as much more of the hormone is readily available by those particular cells.