Half-life

[ipso facto]

My apologies if this has already been done (I didn't see it anywhere), but I thought it might be useful for members to see graphically what the concept of half-life actually means. Testosterone esthers for example, are actively released into the system over a certain period (for testosterone enanthate this is around two weeks), but the release rate is uneven, with a big spike up front. The release rate is dependent upon the concentration of the substance, and that concentration steadily declines. Here is a graph that shows the rate, and remaining dosage over time.

This should give a good idea of why there is an initial kick on the first and second days, and then a more stable release after that. The first graph shows the proportion of dose that is left in the body over about a three week period of time for testosterone enanthate (which has the longest half-life on commonly used compounds ... you can mentally adjust the x-axis of this graph for other compounds). The second shows for a 500mg initial dose, what will be left after a certain number of days.

[mkrulic]

that's an exponentional decay but it doesn't look right for test enan. drop a line down from where the 250mg hits the curve to the x axis (number of days). It puts the half life around 2.5 to 3 days. seems a little short

[ipso facto]

that's an exponentional decay but it doesn't look right for test enan. drop a line down from where the 250mg hits the curve to the x axis (number of days). It puts the half life around 2.5 to 3 days. seems a little short

I've checked and you are right, and I've corrected the graphs. The half-life of TE should be 10.5 days

[ipso facto]

OK ... here's a better chart (more data points) ... anyway, I hope this proves useful

[8pak]

Has it been definitively shown that systemic absorption of an enanthate ester from an intramuscular depot site follows classic first-order pharmacokinetic decay??

[ipso facto]

I don't know that it has for a fact; I'm just doing a little mental exercise here (trying to calculate how much of the stuff might be floating around my body at any time). But I suspect that this is right; here's my reasoning.

The TE is injected into fat surrounded by blood vessels, and the TE seeps into the blood just by migrating around the fat (it's essentially dissolved in the fat). So this is going to follow a standard exponential decay (my charts). My understanding is that the TE gets to circulate once in the blood, and then is deactivated by the liver. So once in the blood, it has a very short half-life, more like pure testosterone, which is polar, water-soluable, and thus can't be stored in the fat.

I thought this might be expanded into a general formula for computing the amount of TE (or other AS) still in the body for a given cycle of doses.