Testosterone Enanthate and Testosterone Cypionate Half-Lives - Data?

[bennettjc]

Good Morning,

When I started I read various things about the half-lives of TCyp and TEnan. 7 days. 10 days. One has a 1 day longer half life because of the longer ester.

I am aware that half-lives of all medications vary depending upon the patient. But a good estimate has clinical value for making general recommendations.

So I decided to look into the data because I am going to be on this, TEnan in my case, forever. And there was not much. In fact nothing regarding TCyp.

I did find one paper addressing TEnan. Comparison of the kinetics of injectable testosterone in eugonadal and hypogonadal men - PubMed (nih.gov) I have the pdf of the paper if anyone wants it. And the answer is - 3.8 days in the eugonadal group and 4.2 days in the hypogonadal group. So until I see data to the contrary I think it is reasonable to say that the half life of Testosterone Enanthate is about 4 days.

I searched here and I did find this table that Nelson posted. Confused about Testosterone Enanthate Half Life
I'll try to track down the citation when I can. The terminal half-life in the graphic for Testosterone Enanthate cited in the graphic was 4.5 days. Close enough!

So if anyone could point me towards other data regarding this issue I'd appreciate it.

And no the PDR does not address half lives specifically for either ester.

Thanks

 

[madman]

Good Morning,

When I started I read various things about the half-lives of TCyp and TEnan. 7 days. 10 days. One has a 1 day longer half life because of the longer ester.

I am aware that half-lives of all medications vary depending upon the patient. But a good estimate has clinical value for making general recommendations.

So I decided to look into the data because I am going to be on this, TEnan in my case, forever. And there was not much. In fact nothing regarding TCyp.

I did find one paper addressing TEnan. Comparison of the kinetics of injectable testosterone in eugonadal and hypogonadal men - PubMed (nih.gov) I have the pdf of the paper if anyone wants it. And the answer is - 3.8 days in the eugonadal group and 4.2 days in the hypogonadal group. So until I see data to the contrary I think it is reasonable to say that the half life of Testosterone Enanthate is about 4 days.

I searched here and I did find this table that Nelson posted. Confused about Testosterone Enanthate Half Life
I'll try to track down the citation when I can. The terminal half-life in the graphic for Testosterone Enanthate cited in the graphic was 4.5 days. Close enough!

So if anyone could point me towards other data regarding this issue I'd appreciate it.

And no the PDR does not address half lives specifically for either ester.

Thanks

I would not fret over whether one uses enanthate vs cypionate as they are basically interchangeable.

Regardless of the minor differences in the esters between the two, there are many other factors that affect the rate at which the testosterone is released from the oily depot at the injection site.

Sub-q vs IM, the volume of injection, injection depth, site of injection, lymphatic flow, the concentration of BOH (benzyl alcohol) is other possible factors that can affect absorption rates of the esterified hormone.

As far as testosterone esters 100 mg of enanthate= 72 mg active testosterone and 100 mg cypionate= 70 mg active testosterone.

If anything I would be far more concerned with your protocol (dose T/injection frequency)/SHBG level and where such has your trough FT levels!

Top it all off that you should be using/relying upon the most accurate assays TT (LC/MS-MS) and FT using the gold standard Equilibrium Dialysis or Ultrafiltration (next best).

 

[madman]

Use the search function and type in half-life as this has been discussed numerous times on here.

 

[madman]

Regarding half-lives keep in mind that a majority of studies on the PK/PD of the various T-esters were done using IM (once weekly/fortnightly) injections in a small number of subjects and most of the literature is from decades ago.

Here is a more recent and in-depth study using TC.




Population Pharmacokinetic/Pharmacodynamic Modeling of Depot Testosterone Cypionate in Healthy Male Subjects (2018)

Youwei Bi Paul J. Perry Touro University California, [email protected] Michael Ellerby Touro University California, [email protected] Daryl J. Murry




DISCUSSION

Following the depot administration of TC, the PKs of tT were satisfactorily described by the one-compartmental model with first-order absorption. The limited number of samples in the absorption phase (1–2 samples per subject) prevents using a more plausible absorption model for the high lipophilicity of testosterone in an oil base and administered i.m., such as a mixed zero-order and first-order model with lag time.

*This could lead to flip-flop PKs and can cause difficulties in the estimation and interpretation of PK parameters. The half-life of testosterone undecanoate (TU) following oral administration is around 150 minutes, which is very different from the half-life estimate of 21–34 days following the i.m. injection of TU reported by Behre et al. The large difference in half-lives of TU between oral and i.m. formulation suggests that flip-flop PKs are occurring with testosterone esters, which is also reported in the published literature and for the i.m. injection of nandrolone.

*The i.m. injection of TC is also likely to have flip-flop kinetics, in such a scenario, diffusion, and release from an oily depot site is the rate-limiting step to systemic availability.

It is difficult to calculate the PK parameters of TC using traditional noncompartmental methods, especially when the endogenous testosterone secretion rate is suppressed during the course of TC administration and the testosterone secretion rate is regulated by the LH-testosterone feedback loop system in the HPG axis. Our estimated post hoc median tT half-life was 4.05 days, which is shorter than the mean reported elimination half-life of 6.9 days determined using noncompartmental analysis. Such inconsistency is believed to result from failure to consider endogenous testosterone production. When we assume endogenous testosterone secretion is 0 in the PPK analysis, the median estimated half-life increases to 6.87 days.

 

[madman]

If you want to dig deeper go nuts!

Fundamental understanding of drug absorption from a parenteral oil depot

Abstract Oil depots are parenteral drug formulations meant for sustained release of lipophilic compounds. Until now, a comprehensive understanding of the mechanism of drug absorption from oil depots is lacking. The aim of this paper was to fill this gap. A clinical study with healthy...

www.excelmale.com

Spatial distribution of oil depots monitored in human muscle using MRI

Abstract Oil depots are parenteral drug formulations meant for the sustained release of lipophilic compounds. According to mass transport models, the drug-release rate from these injections is determined by the surface area of the oil depot. Until now, the size of the surface area of injected...

www.excelmale.com

 

[bennettjc]

T

Regarding half-lives keep in mind that a majority of studies on the PK/PD of the various T-esters were done using IM (once weekly/fortnightly) injections in a small number of subjects and most of the literature is from decades ago.

Here is a more recent and in-depth study using TC.




Population Pharmacokinetic/Pharmacodynamic Modeling of Depot Testosterone Cypionate in Healthy Male Subjects (2018)

Youwei Bi Paul J. Perry Touro University California, [email protected] Michael Ellerby Touro University California, [email protected] Daryl J. Murry




DISCUSSION

Following the depot administration of TC, the PKs of tT were satisfactorily described by the one-compartmental model with first-order absorption. The limited number of samples in the absorption phase (1–2 samples per subject) prevents using a more plausible absorption model for the high lipophilicity of testosterone in an oil base and administered i.m., such as a mixed zero-order and first-order model with lag time.

*This could lead to flip-flop PKs and can cause difficulties in the estimation and interpretation of PK parameters. The half-life of testosterone undecanoate (TU) following oral administration is around 150 minutes, which is very different from the half-life estimate of 21–34 days following the i.m. injection of TU reported by Behre et al. The large difference in half-lives of TU between oral and i.m. formulation suggests that flip-flop PKs are occurring with testosterone esters, which is also reported in the published literature and for the i.m. injection of nandrolone.

*The i.m. injection of TC is also likely to have flip-flop kinetics, in such a scenario, diffusion, and release from an oily depot site is the rate-limiting step to systemic availability.

It is difficult to calculate the PK parameters of TC using traditional noncompartmental methods, especially when the endogenous testosterone secretion rate is suppressed during the course of TC administration and the testosterone secretion rate is regulated by the LH-testosterone feedback loop system in the HPG axis. Our estimated post hoc median tT half-life was 4.05 days, which is shorter than the mean reported elimination half-life of 6.9 days determined using noncompartmental analysis. Such inconsistency is believed to result from failure to consider endogenous testosterone production. When we assume endogenous testosterone secretion is 0 in the PPK analysis, the median estimated half-life increases to 6.87 days.

This paper is pretty much what I am looking for.
Thanks