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Testosterone Replacement, Low T, HCG, & Beyond
Testosterone Basics & Questions
Is the feeling of "well being" on TRT, dosage dependent?
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<blockquote data-quote="madman" data-source="post: 184259" data-attributes="member: 13851"><p><strong>Pharmacokinetic Profile of Subcutaneous Testosterone Enanthate Delivered via a Novel, Prefilled Single-Use Autoinjector: A Phase II Study</strong></p><p><span style="color: rgb(184, 49, 47)">Jed Kaminetsky, MD, Jonathan S. Jaffe, MD, and Ronald S. Swerdloff, MD </span></p><p></p><p></p><p></p><p></p><p>Most of the information we have based on the half-life (esterified T) was done using IM.</p><p></p><p>They do state <em>T1/2 (SD) was 239.63 hours (59.93) for 100 mg SC TE</em></p><p></p><p>Because of rising T levels at later time points in the 50 mg arm, a reliable estimation of half‐life (T1/2) of this dose was not possible. <span style="color: rgb(184, 49, 47)">The apparent T1/2 (SD) was 239.63 hours (59.93) for 100 mg SC TE</span> and 172.57 hours (34.74) for 200 mg IM T</p><p></p><p></p><p><strong>Table 2 </strong></p><p><span style="color: rgb(184, 49, 47)">Mean T½—h (SD) 239.63</span></p><p></p><p></p><p></p><p></p><p><strong>Pharmacology of testosterone preparations </strong></p><p><span style="color: rgb(184, 49, 47)">H.M. Behre, C. Wang, D.J. Handelsman and E. Nieschlag </span></p><p></p><p>[ATTACH=full]10349[/ATTACH]</p><p></p><p></p><p></p><p></p><p><span style="color: rgb(0, 0, 0)"><strong>Population Pharmacokinetic/Pharmacodynamic Modeling of Depot Testosterone Cypionate in Healthy Male Subjects </strong></span></p><p><span style="color: rgb(184, 49, 47)">Youwei Bi Paul J. Perry Touro University California, <a href="mailto:paul.perry@tu.edu">paul.perry@tu.edu</a> Michael Ellerby Touro University California, <a href="mailto:michael.ellerby@tu.edu">michael.ellerby@tu.edu</a> Daryl J. Murry </span></p><p></p><p></p><p></p><p></p><p>Cypionate study states the mean/median having a much shorter half-life.</p><p></p><p></p><p><strong>DISCUSSION </strong></p><p></p><p>Following the depot administration of TC, the PKs of tT were satisfactorily described by the one-compartmental model with first-order absorption. <span style="color: rgb(184, 49, 47)"><em><strong>The limited number of samples in the absorption phase (1–2 samples per subject) <u>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</u>.16</strong></em></span> <span style="color: rgb(44, 130, 201)"><strong><u><em>This could lead to flip-flop PKs and can cause difficulties in the estimation and interpretation of PK parameters</em></u></strong><em><strong>.17</strong> </em></span>The half-life of testosterone undecanoate (TU) following oral administration is around 150 minutes,18 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. 19 <em><span style="color: rgb(44, 130, 201)"><strong>The large difference in half-lives of TU between oral and i.m. formulation <u>suggests that</u></strong></span></em><span style="color: rgb(44, 130, 201)"> <em><u><strong>f<u>li</u>p-flop PKs are occurring with testosterone esters</strong></u>, which is also reported in the published literature20 and for the i.m. injection of nandrolone.21 <strong><u>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</u>.</strong></em></span></p><p></p><p><em><span style="color: rgb(184, 49, 47)"><u><strong>It is difficult to calculate the PK parameters of TC using traditional noncompartmental methods</strong></u><strong>, </strong>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 HPG axis.</span></em> <span style="color: rgb(26, 188, 156)"><strong><u>Our estimated post hoc median tT half-life was 4.05 days,</u></strong></span><span style="color: rgb(184, 49, 47)"><strong><u> which is shorter than the mean reported elimination half-life of 6.9 days determined using noncompartmental analysis</u>.</strong>11 Such inconsistency is believed to result from failure to consider endogenous testosterone production.</span> <span style="color: rgb(184, 49, 47)"><strong><u>When we <strong>assume</strong> endogenous testosterone secretion is 0 in the PPK analysis, the median estimated half-life increases to 6.87 days</u>.</strong> </span></p></blockquote><p></p>
[QUOTE="madman, post: 184259, member: 13851"] [B]Pharmacokinetic Profile of Subcutaneous Testosterone Enanthate Delivered via a Novel, Prefilled Single-Use Autoinjector: A Phase II Study[/B] [COLOR=rgb(184, 49, 47)]Jed Kaminetsky, MD, Jonathan S. Jaffe, MD, and Ronald S. Swerdloff, MD [/COLOR] Most of the information we have based on the half-life (esterified T) was done using IM. They do state [I]T1/2 (SD) was 239.63 hours (59.93) for 100 mg SC TE[/I] Because of rising T levels at later time points in the 50 mg arm, a reliable estimation of half‐life (T1/2) of this dose was not possible. [COLOR=rgb(184, 49, 47)]The apparent T1/2 (SD) was 239.63 hours (59.93) for 100 mg SC TE[/COLOR] and 172.57 hours (34.74) for 200 mg IM T [B]Table 2 [/B] [COLOR=rgb(184, 49, 47)]Mean T½—h (SD) 239.63[/COLOR] [B]Pharmacology of testosterone preparations [/B] [COLOR=rgb(184, 49, 47)]H.M. Behre, C. Wang, D.J. Handelsman and E. Nieschlag [/COLOR] [ATTACH type="full" alt="Screenshot (1749).png"]10349[/ATTACH] [COLOR=rgb(0, 0, 0)][B]Population Pharmacokinetic/Pharmacodynamic Modeling of Depot Testosterone Cypionate in Healthy Male Subjects [/B][/COLOR] [COLOR=rgb(184, 49, 47)]Youwei Bi Paul J. Perry Touro University California, [EMAIL]paul.perry@tu.edu[/EMAIL] Michael Ellerby Touro University California, [EMAIL]michael.ellerby@tu.edu[/EMAIL] Daryl J. Murry [/COLOR] Cypionate study states the mean/median having a much shorter half-life. [B]DISCUSSION [/B] Following the depot administration of TC, the PKs of tT were satisfactorily described by the one-compartmental model with first-order absorption. [COLOR=rgb(184, 49, 47)][I][B]The limited number of samples in the absorption phase (1–2 samples per subject) [U]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[/U].16[/B][/I][/COLOR][B] [/B][COLOR=rgb(44, 130, 201)][B][U][I]This could lead to flip-flop PKs and can cause difficulties in the estimation and interpretation of PK parameters[/I][/U][/B][I][B].17[/B] [/I][/COLOR]The half-life of testosterone undecanoate (TU) following oral administration is around 150 minutes,18 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. 19 [I][COLOR=rgb(44, 130, 201)][B]The large difference in half-lives of TU between oral and i.m. formulation [U]suggests that[/U][/B][/COLOR][/I][COLOR=rgb(44, 130, 201)][U] [/U][I][U][B]f[U]li[/U]p-flop PKs are occurring with testosterone esters[/B][/U], which is also reported in the published literature20 and for the i.m. injection of nandrolone.21 [B][U]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[/U].[/B][/I][/COLOR] [I][COLOR=rgb(184, 49, 47)][U][B]It is difficult to calculate the PK parameters of TC using traditional noncompartmental methods[/B][/U][B], [/B]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 HPG axis.[/COLOR][/I][COLOR=rgb(184, 49, 47)] [/COLOR][COLOR=rgb(26, 188, 156)][B][U]Our estimated post hoc median tT half-life was 4.05 days,[/U][/B][/COLOR][COLOR=rgb(184, 49, 47)][B][U] which is shorter than the mean reported elimination half-life of 6.9 days determined using noncompartmental analysis[/U].[/B]11 Such inconsistency is believed to result from failure to consider endogenous testosterone production.[/COLOR] [COLOR=rgb(184, 49, 47)][B][U]When we [B]assume[/B] endogenous testosterone secretion is 0 in the PPK analysis, the median estimated half-life increases to 6.87 days[/U].[/B] [/COLOR] [/QUOTE]
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Testosterone Replacement, Low T, HCG, & Beyond
Testosterone Basics & Questions
Is the feeling of "well being" on TRT, dosage dependent?
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