It’s common for published values to be different, because pharmacokinetic studies are often performed on only a few subjects at a time, and there can be considerable variability between subjects. Further, there ends up being a confusion between the elimination process and the distribution process, which is variable particularly in the earlier part of the process. For example, reported half-life values for Muscle powder Deca Nandrolone Decanoate in humans range from 7 to 12 days.
For this reason, it’s best to not take any one report overly literally, but instead to get the best reading of all the data that’s available. Fortunately, for oral anabolic steroid the half life is very closely related to a predictable property, the partition coefficient (this is generally approximately equal to the ratio between lipid solubility and water solubility). Where the only difference between two steroid esters is the number of carbons – arrangement being the same or similar! – then each added carbon adds about a day to the half life.
With this information, to make a best estimate for the half life of one steroid, data from similar steroids can be used as well.
For purposes of calculating recovery or for calculating frontloading, these figures have always worked well for anabolic steroid half lives:
· Acetate esters: About 1 day
· Propionate esters: About 2 days
· Phenylpropionate esters: About 3 days
· Enanthate esters: About 5 days
· Cypionate esters: About 6 days
· Decanoate esters: About 10 days
· Undecanoate esters: Really not established from practice. From extrapolation, probably about 11 days. Does not appear to be over about 14 days, or much if any less than 11 days. I use 14 days for recovery calculation in the case of Equipose Boldenone undecanoate liquid, though that might be a larger number than necessary.
With regard to the parent steroid, theory would suggest adding a day for 19-nor, subtracting some small amount for 5-alpha reduction, or adding some small amount for having more than one double bond, and some unknown adjustment for drug metabolism differences. But in practice there seems no need for such adjustments. Accounting for the ester alone seems sufficient.
T3’s half life is variable between individuals but roughly speaking is about a day. There would be no use for a numeric value in practice because Cytomel T3 should not be frontloaded, and calculating what day it has cleared is not important.
Clenbuterol’s half life is about a day and a half.
Clomiphene, tamoxifen, and toremifene all have half lives of about 5 days. The anti-aromatases Arimidex Anastrozole and Femara Letrozole have half lives of about 2 days.