Partition Coefficiant
Oral bioavailability is not only an issue of oil-solubility, though. The measure of a steroid's partition coefficient can be even more important to designing an effective lymphatically delivered softgel. To be simple, "partition coefficient" is a measure of how much a particular substance likes to be dissolved in oil compared to water (although something may dissolve well in oil, it may dissolve well in water too). It allows us to determine how well it is going to stay dissolved in oil, once we put it in there. If the PC measure is not sufficiently high, the compound will leave the oil once it enters the watery environment of the stomach, ruining any chance of delivering it to the lymphatic system (which allows us to bypass the destructive first-pass through the liver). To date, 1-testosterone hexyldecanoate offers us a higher partition coefficient value than any form of 1-testosterone ever developed. This means not only can we dissolve more 1-testosterone in each softgel, but milligram for milligram a lot more is going to stay dissolved in oil once you take it, and a lot more is going to make its way into circulation (and to your muscles).
Partition Coefficient Values of Various 1-Testosterone Products:
1-Testosterone (free base) LogP 3.5
1-Testosterone Ethylcarbonate LogP 4.9
1-Testosterone THP Ether LogP 5.6
1-Testosterone Undecanoate LogP 8.3
1-Testosterone Hexyldecanoate LogP 9.8