Some results from my Depo-T Absorption Calculator

[ASaxon]

He does have a point though, which is that we may not be using the correct model and that the 1/2 life is meaningless. However, for us interested in replicating that graph, the decay model works and I have not seen another model that does as good a job. In addition, any other model could not decay substantially faster than a radioactive decay model with 1/2 life of 7-8 days and still fit those data.

I guess the only way to see the “true” graph of testosterone decay by direct blood testing is to take a masochistic eunuch and keep them off of testosterone for six months and then inject them and take blood tests. LOL, any volunteers?

Also I should mention that the time to steady-state is partially contolled by the 1/2 life. For a 4 day 1/2 life one would only have to wait 3 weeks to reach steady-state with weekly injections and not front-loading the first injection. For 8 day 1/2 life it is ~5 weeks (although ~3 weeks with a doubling of the first injection).

Yea, looking at the graphs you’re right.

Hey I just got a cool result. Try doubling up the first injection and put in a 1/2 life of 4 days with weekly injects - I don't think anyone would do that in practice if they thought the 1/2 life was only 4 days!

Hehe, another good point. If the half life was 4 days then no one would ever double the first dose because absorption would look something like the attached graph.

View attachment 6416

Note, I know, there are no peaks...this is a work in progress. Still it works really well.

BTW, I think I'm gonna go ahead an put in a ramp up in my calculator. Shouldn't be too hard. And it will get rid of the peaks.

 

[SWALE]

Good thread, guys! I LIKE the way it makes my head hurt.

I clearly am no Pharmacologist--although sometmes wish I were. So I have had to roll up my sleaves, read thousands of lab reports, listen to patients (preferable to reading thousands of lab reports), and continue to think.

The real goal here is not to determine actual serum concentrations of free hormones (now figure THAT one in!) but rather to effectively guage and predict response. That is, applying the requisite association between a calculated half-life and its application as a legitimate biomarker for clinical response.

So we then must figure in differences in activity level, actions of the various isozymes involved in metabolism of the hormones, and overall health of the patient. All affect absorbtion and metabolism of the injected medication.

My experience tells me that the useful half-life for the cypionate ester is somewhere between 5 and 8 days. Stacking previous injections and their decay, along with HPTA reaction and restabilization, is why I wait 6 weeks between initiation of TRT and follow-up monitoring.

This is also one of the reasons I like to add in a bit ("bit" is a pharmacological phrase; roughly twice the dose of a "smidgeon") of HCG on days five and six of the injection week, in order to smooth out serum androgen levels. It used to be days six and seven, but looking at labs made me slide it forward one day.

Just the musings of an old roll-up-his-sleaves country doc...