EAT A DICK CIRCUITBOY!!
Circuitboy said:
SO NO DECEM ALL TESTOSTERONES ARE ALIKE...... So maybe you should do some more research
Injectable anabolic steroids are usually available as esters of the parent drugs. Often, a drug in its original form may lack certain properties that are desired: for example, good solubility in oil or fat. There may be a part of the molecule to which one may add an additional chemical group to give the new molecule desired properties, but in such a way that over time in the body, the modification will be removed, restoring the parent drug. If the modified molecule is itself not active, needing to be converted back to the parent drug, then this is a prodrug. Anabolic steroids such as testosterone cypionate and nandrolone decanoate are prodrugs. Since esters of anabolic steroids are so often used in bodybuilding, in this article we will examine them closely.
At a particular position (#17) all anabolic steroids have a hydroxy group, consisting of an oxygen and hydrogen, represented by OH. This can be replaced by an ester group: for example, propionate (OOCCH2CH3). This results in improvement in solubility in oil and reduction of water solubility, both of which are useful for reasons later to be discussed.
--------------------------------------------------------------------------------
How do esters differ in structure?
While quite an array of names exist and make the issue seem complicated, the main difference between different esters is simply the number of carbon atoms in the ester. Propionate, as shown above, has three carbons, whereas acetate has two, isobutyrate has four, enanthate has seven, cypionate has eight, and decanoate has ten. On occasion there are more unusual esters, such as cyclohexylmethylcarbonate (used in Parabolan) which has eight carbons and one more oxygen than the above esters do.
--------------------------------------------------------------------------------
How do esters change the physical properties of steroids?
Testosterone, nandrolone, and other anabolic steroids have poor solubility in either water or oil. Esterifying them improves oil solubility. This enables useful dosages of perhaps 100 mg or more per cc. But the more carbons the ester has, the lower the water solubility becomes, and the higher the partition coefficient (ratio between lipid and water solubilities) becomes. If the partition coefficient is high, then at any moment a high proportion of the prodrug is dissolved in oil or body fat, and only a small proportion is dissolved in water.
This is important. If testosterone itself is given in oil solution, it transfers too easily from oil to the water in the blood. The result is that an oil injection of testosterone gives a sudden spike in testosterone levels, which rapidly drops. Injections would be required at least twice per day, and perhaps even more often. Improving the oil solubility and decreasing the water solubility slows this transfer, and extends the half-life of the drug to several days or more.
The number of carbons also has a small effect in that it reduces the parent drug’s proportion of the total weight. E.g., it would take 344 mg of testosterone propionate, or 401 mg of testosterone enanthate to give the same amount of testosterone as in 288 mg of testosterone suspension.
How are esters converted back to the parent drug?
The ester bond is fairly easily broken under the right conditions. If the molecule is dissolved in water, this can occur by a simple chemical reaction, yielding the parent drug and a carboxylic acid. For example, if the steroid used is testosterone propionate, testosterone and propionic acid are released. Carboxylic acids are safe and natural in the body in reasonable amounts. It should not be thought that these are strong acids because they are not: they are acids in the same sense that, e.g., Vitamin C or lactic acid are acids. Furthermore, the amount of carboxylic acid present at any time is extremely low.
The carboxylic acids do not have any activities of interest. Once the ester group is removed, it has done its job, and the parent drug acts in its normal manner.
Besides the simple chemical hydrolysis described above, the esters can be removed by enzymes in the blood called esterases, though water still is required for the reaction. The great majority of hydrolysis occurs with the help of these enzymes or by non-specific reactions with proteins. These reaction cannot take place while the esterified steroid is dissolved in fat. Thus, while the esterified steroids are dissolved in fat, they are protected from hydrolyis, and thus serve as a depot for the drug, giving extended duration of action.
What are the half-lives of different esters?
Shorter chain esters have shorter half-lives, because of their lower partition coefficient. Testosterone cypionate has a half-life of 8 days5, the enanthate ester has a half-life of 4 days6, and nandrolone decanoate has a half-life of 8 days7. These figures are only approximate. The difference between these values for cypionate and enanthate probably includes difference attributable to different measuring techniques. The actual difference is probably not more than two days.
In the rat, where half-lives of anabolic steroid esters are similar to those in humans but somewhat shorter, the half-lives of the phenylpropionate, decanoate, and laurate esters are 1, 5, and 10 days respectively.3 The same trend would be expected in man.
Half-life is linearly related to log partition coefficient, which is itself linearly related to the carbon chain length, the exception being if the ester is an unusual one such as phenylpropionate. This was shown by James et al.3 for the formate through valerate esters of testosterone in the rat. The half-life of testosterone propionate was approximately 4 days, and each carbon added to or subtracted from that chain length changed half-life by about 1.5 days.
How are steroid esters made?
The most convenient method of synthesis of steroid esters is reaction of the steroid in a 2:1 mixture of pyridine and the anhydride of the desired ester: for example, propionic anhydride would be used to make the propionate ester. A large excess (at least 10 times) of the anhydride compared to the steroid would be required. This would then be purified by diluting with at least 10 parts of water to each part of pyridine, adding 1 part ether, decanting the water after shaking, and then washing with 10 parts water repeatedly in a separatory funnel. This would be followed preferably by recrystallization or chromatography for purification.
While the theory of the effects of esterification of steroids is interesting and somewhat complicated, the practical implications are simple. Differences between parent drugs are far more important than differences between esters of the same drug. And if the ester is different, the key difference to the bodybuilder is in half-life of the drug. Longer half-lives add convenience, and shorter-half lives allow the drug to exit the body more quickly. Besides these things, however, there are no significant differences between drugs resulting from use of different esters.