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Testosterone Replacement, Low T, HCG, & Beyond
Testosterone Basics & Questions
Tips on how to blend propionate with enanthate (or cypionate)?
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<blockquote data-quote="madman" data-source="post: 205344" data-attributes="member: 13851"><p>Indeed!</p><p></p><p></p><p><strong>Bioavailability and LH-Suppressing Effect of Different Testosterone Preparations in Normal and Hypogonadal Men (1976)</strong></p><p></p><p>[ATTACH=full]15735[/ATTACH]</p><p>[ATTACH=full]15736[/ATTACH]</p><p>[ATTACH=full]15737[/ATTACH]</p><p></p><p></p><p></p><p></p><p></p><p><strong>Pharmacokinetic Properties of Testosterone Propionate in Normal Men (1986)</strong></p><p><strong></strong></p><p><strong></strong></p><p><strong>ABSTRACT</strong></p><p></p><p><em>The pharmacokinetic characteristics of testosterone propionate were studied in normal men after a single IM dose of 25 mg testosterone propionate-19,i9,19-d3; Plasma levels of testosterone propionate-19,19,19-d3, its active metabolite testosterone-i9,19,19-d3, and endogenous testosterone were measured by gas chromatography-mass spectrometry. Testosterone propionate-19,19, l9-d3 was gradually transferred from the IM injection site to the systemic circulation. <strong><em>The plasma levels of testosterone propionate-19,l9,19-c<3 were maintained at 2-4 ng/ ml between 3 and 36 h after administration. </em></strong></em><strong><em><u>Plasma testosterone-i9,19,19-d3 levels were maintained above the physiological testosterone level for 48 h</u>,</em></strong><em> while plasma levels of endogenous testosterone changed little. (j Clin Endocrinol Metab 63: 1361, 1986)</em></p><p></p><p></p><p></p><p></p><p><strong>Testosterone propionate-19-d3 administration studies </strong></p><p></p><p><em>The study subjects were two normal men, 27 and 24 yr old, weighing 72 and 61 kg, respectively. </em><strong><em>To determine the secretory dynamics of endogenous testosterone, heparinized blood samples (10 ml) were obtained at 0800; 1100, 1400,1700, and 2000 h for 4 days. <u>The men then were given 25 mg testosterone propionate-19-d3, IM, at 0800 h</u>. <u>Ten-milliliter heparinized blood samples were obtained 5 min before and 3, 6, 9, 12, 24, 27, 30, 33, 36, 48, 54, 60, 72, 78, and 84 h after dosing</u>. Plasma was separated by centrifugation and stored at -20 C until analysis.</em></strong></p><p><strong></strong></p><p><strong></strong></p><p><strong></strong></p><p><strong></strong></p><p><strong>Results </strong></p><p><strong></strong></p><p><strong>Endogenous plasma testosterone profiles</strong></p><p></p><p><em>Before studying the disposition of testosterone propionate, we determined the levels of endogenous plasma testosterone for 4 days in the two normal men (Fig. 1). </em><strong><em>The mean plasma testosterone concentration in subject 1 was 6.6 ng/ml, with a range of 4.0-8.9 ng/ml. Subject 2 had a mean value of 6.9 ng/ml and a range of 4.7-9.3 ng/ml. <u>Testosterone concentrations had a circadian rhythm, with the highest levels between 0800 and 1100 h and the lowest levels between 1700 and 2000 h in both men</u>.</em></strong></p><p><strong></strong></p><p><strong></strong></p><p><strong></strong></p><p><strong>FIG. 1. Plasma testosterone profiles in subjects 1 and 2.</strong></p><p></p><p>[ATTACH=full]15738[/ATTACH]</p><p>[ATTACH=full]15739[/ATTACH]</p><p></p><p></p><p></p><p></p><p><strong>Plasma testosterone propionate-19-d3 and testosterone19-da concentrations </strong></p><p><strong></strong></p><p><strong><em>Plasma testosterone propionate-19-d3 levels were maintained at 2-4 ng/ml between 3 and 36 h after IM administration of a single 25-mg dose of testosterone propionate-19-d3 (Fig. 2) and thereafter decreased very slowly. Testosterone-19-d3 was detected in the first blood sample taken 3 h after the injection. <u>The maximum plasma testosterone-19-d3 levels (15.0 ng/ml for subject 1 and 11.5 ng/ml for subject 2) occurred between 24 and 27 h</u>.</em></strong><em> Thereafter, the decline of testosterone-19-d3 was parallel to that of testosterone propionate-19-d3 in both subjects. The pharmacokinetic parameters characterizing the disposition of testosterone propionate-19-d3 and testosterone-19-d3 are summarized in Table 1.</em></p><p></p><p></p><p><strong>Effect of testosterone propionate-19-d^ on plasma endogenous testosterone </strong></p><p></p><p><em>Endogenous plasma testosterone levels were measured at various times for 84 h after the IM testosterone propionate-19-d3 injection. The results are shown in Fig. 2. Endogenous testosterone levels just before the administration of testosterone prOpionate-19-d3 were 7.2 ng/ml in subject 1 and 7.5 ng/ml in subject 2. After the administration of testosterone propionate-19-d3, endogenous testosterone levels varied between 3.8 and 7.8 ng/ml and 4.4 and 7.5 ng/ml in subjects 1 and 2, respectively.</em></p><p></p><p></p><p><strong>FlG. 2. Plasma concentrations of testosterone propionate-19-d3 (■ ■), testosterone-19-d3 (O O), and endogenous testosterone (• •) vs. time in subjects 1 and 2. An IM dose of 25 mg testosterone propionate-19-d3 was given to the two normal men at 0800 h</strong></p><p>[ATTACH=full]15741[/ATTACH]</p><p></p><p><em>[ATTACH=full]15740[/ATTACH]</em></p><p></p><p></p><p></p><p></p><p></p><p></p><p></p><p><strong>Discussion</strong><em> </em></p><p><em></em></p><p><em>The use of GC-MS and stable isotopically labeled drugs as tracers make it possible to provide a precise analytical method for both the parent compound and metabolites with high sensitivity and selectivity (20-22). </em><strong><em>The application of this method allowed us to follow the plasma levels of testosterone propionate-19-d3 and its active metabolite testosterone-19-d3 for 84 h after the IM administration of testosterone propionate-19-d3.</em></strong></p><p></p><p><em>Intramuscularly administered testosterone propionate-19-d3 was readily detected in the circulation, demonstrating clearly that the testosterone propionate-19-d3 was transferred from the injection site in the muscle to the systemic circulation.</em></p><p><em></em></p><p><em></em></p><p><em></em></p><p><em></em></p><p><em>*Nieschlag et al. (8) measured the total plasma exogenous and endogenous testosterone levels by RIA after the IM administration of 25 mg testosterone propionate to normal men. Total plasma testosterone levels were maintained above the physiological levels for 24 h after drug administration. However, it was not possible to determine exactly the contribution of administered testosterone propionate to the total concentration of circulating testosterone. </em><strong><em>With the aid of the double isotope dilution assay employed in this study, endogenous testosterone and testosterone derived from administered testosterone propionate could be differentiated easily. Conversion of testosterone propionate-19-d3 to testosterone-19-d3 was fast in the systemic circulation, and testosterone propionate-19-d3 injection resulted in exogenous testosterone levels above the normal testosterone level (>4 ng/ml) for 48 h. Moreover, exogenous testosterone continued to contribute to the total plasma levels for up to 84 h.</em></strong></p></blockquote><p></p>
[QUOTE="madman, post: 205344, member: 13851"] Indeed! [B]Bioavailability and LH-Suppressing Effect of Different Testosterone Preparations in Normal and Hypogonadal Men (1976)[/B] [ATTACH type="full" alt="Screenshot (6325).png"]15735[/ATTACH] [ATTACH type="full" alt="Screenshot (6326).png"]15736[/ATTACH] [ATTACH type="full" alt="Screenshot (6327).png"]15737[/ATTACH] [B]Pharmacokinetic Properties of Testosterone Propionate in Normal Men (1986) ABSTRACT[/B] [I]The pharmacokinetic characteristics of testosterone propionate were studied in normal men after a single IM dose of 25 mg testosterone propionate-19,i9,19-d3; Plasma levels of testosterone propionate-19,19,19-d3, its active metabolite testosterone-i9,19,19-d3, and endogenous testosterone were measured by gas chromatography-mass spectrometry. Testosterone propionate-19,19, l9-d3 was gradually transferred from the IM injection site to the systemic circulation. [B][I]The plasma levels of testosterone propionate-19,l9,19-c<3 were maintained at 2-4 ng/ ml between 3 and 36 h after administration. [/I][/B][/I][B][I][U]Plasma testosterone-i9,19,19-d3 levels were maintained above the physiological testosterone level for 48 h[/U],[/I][/B][I] while plasma levels of endogenous testosterone changed little. (j Clin Endocrinol Metab 63: 1361, 1986)[/I] [B]Testosterone propionate-19-d3 administration studies [/B] [I]The study subjects were two normal men, 27 and 24 yr old, weighing 72 and 61 kg, respectively. [/I][B][I]To determine the secretory dynamics of endogenous testosterone, heparinized blood samples (10 ml) were obtained at 0800; 1100, 1400,1700, and 2000 h for 4 days. [U]The men then were given 25 mg testosterone propionate-19-d3, IM, at 0800 h[/U]. [U]Ten-milliliter heparinized blood samples were obtained 5 min before and 3, 6, 9, 12, 24, 27, 30, 33, 36, 48, 54, 60, 72, 78, and 84 h after dosing[/U]. Plasma was separated by centrifugation and stored at -20 C until analysis.[/I] Results Endogenous plasma testosterone profiles[/B] [I]Before studying the disposition of testosterone propionate, we determined the levels of endogenous plasma testosterone for 4 days in the two normal men (Fig. 1). [/I][B][I]The mean plasma testosterone concentration in subject 1 was 6.6 ng/ml, with a range of 4.0-8.9 ng/ml. Subject 2 had a mean value of 6.9 ng/ml and a range of 4.7-9.3 ng/ml. [U]Testosterone concentrations had a circadian rhythm, with the highest levels between 0800 and 1100 h and the lowest levels between 1700 and 2000 h in both men[/U].[/I] FIG. 1. Plasma testosterone profiles in subjects 1 and 2.[/B] [ATTACH type="full" alt="Screenshot (6328).png"]15738[/ATTACH] [ATTACH type="full" alt="Screenshot (6329).png"]15739[/ATTACH] [B]Plasma testosterone propionate-19-d3 and testosterone19-da concentrations [I]Plasma testosterone propionate-19-d3 levels were maintained at 2-4 ng/ml between 3 and 36 h after IM administration of a single 25-mg dose of testosterone propionate-19-d3 (Fig. 2) and thereafter decreased very slowly. Testosterone-19-d3 was detected in the first blood sample taken 3 h after the injection. [U]The maximum plasma testosterone-19-d3 levels (15.0 ng/ml for subject 1 and 11.5 ng/ml for subject 2) occurred between 24 and 27 h[/U].[/I][/B][I] Thereafter, the decline of testosterone-19-d3 was parallel to that of testosterone propionate-19-d3 in both subjects. The pharmacokinetic parameters characterizing the disposition of testosterone propionate-19-d3 and testosterone-19-d3 are summarized in Table 1.[/I] [B]Effect of testosterone propionate-19-d^ on plasma endogenous testosterone [/B] [I]Endogenous plasma testosterone levels were measured at various times for 84 h after the IM testosterone propionate-19-d3 injection. The results are shown in Fig. 2. Endogenous testosterone levels just before the administration of testosterone prOpionate-19-d3 were 7.2 ng/ml in subject 1 and 7.5 ng/ml in subject 2. After the administration of testosterone propionate-19-d3, endogenous testosterone levels varied between 3.8 and 7.8 ng/ml and 4.4 and 7.5 ng/ml in subjects 1 and 2, respectively.[/I] [B]FlG. 2. Plasma concentrations of testosterone propionate-19-d3 (■ ■), testosterone-19-d3 (O O), and endogenous testosterone (• •) vs. time in subjects 1 and 2. An IM dose of 25 mg testosterone propionate-19-d3 was given to the two normal men at 0800 h[/B] [ATTACH type="full" alt="Screenshot (6330).png"]15741[/ATTACH] [I][ATTACH type="full" alt="1627142633595.png"]15740[/ATTACH][/I] [B]Discussion[/B][I] The use of GC-MS and stable isotopically labeled drugs as tracers make it possible to provide a precise analytical method for both the parent compound and metabolites with high sensitivity and selectivity (20-22). [/I][B][I]The application of this method allowed us to follow the plasma levels of testosterone propionate-19-d3 and its active metabolite testosterone-19-d3 for 84 h after the IM administration of testosterone propionate-19-d3.[/I][/B] [I]Intramuscularly administered testosterone propionate-19-d3 was readily detected in the circulation, demonstrating clearly that the testosterone propionate-19-d3 was transferred from the injection site in the muscle to the systemic circulation. *Nieschlag et al. (8) measured the total plasma exogenous and endogenous testosterone levels by RIA after the IM administration of 25 mg testosterone propionate to normal men. Total plasma testosterone levels were maintained above the physiological levels for 24 h after drug administration. However, it was not possible to determine exactly the contribution of administered testosterone propionate to the total concentration of circulating testosterone. [/I][B][I]With the aid of the double isotope dilution assay employed in this study, endogenous testosterone and testosterone derived from administered testosterone propionate could be differentiated easily. Conversion of testosterone propionate-19-d3 to testosterone-19-d3 was fast in the systemic circulation, and testosterone propionate-19-d3 injection resulted in exogenous testosterone levels above the normal testosterone level (>4 ng/ml) for 48 h. Moreover, exogenous testosterone continued to contribute to the total plasma levels for up to 84 h.[/I][/B] [/QUOTE]
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Testosterone Replacement, Low T, HCG, & Beyond
Testosterone Basics & Questions
Tips on how to blend propionate with enanthate (or cypionate)?
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