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Testosterone Basics & Questions
Xyosted
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<blockquote data-quote="madman" data-source="post: 203291" data-attributes="member: 13851"><p><strong>Fundamental understanding of drug absorption from a parenteral oil depot (2016)</strong></p><p><strong></strong></p><p><strong></strong></p><p><strong>CONCLUSIONS</strong></p><p></p><p>It is interesting to realize that drug absorption from an oil depot cannot entirely be described by a simple two-phase mass transfer model where concentration gradients, diffusion, and partition coefficients would enable the calculation of the expected absorption.<strong><em> It is demonstrated in this dissertation that there is a role of the excipient BOH in yielding an initially high absorption. </em></strong>The oil depot forms a continuous phase after injection but will be dispersed and encapsulated at the injection site after some days. <strong><em>This in turn largely influences the way the prodrug becomes available; after release from the oil depot,</em></strong> it is present in the interstitial fluid which is drained through the lymph into the systemic circulation. Subsequently, the prodrug permeates through the wall of blood cells and is hydrolyzed. Both the lymph transport and the cell wall permeation take time which is expressed in a lag time. <strong><em>This lag time is different for each injection site: <u>a subcutaneously administered prodrug will enter the systemic circulation via a short path and at a low drainage flow</u>. <u>This results in a short lag time and a slow absorption rate constant of the prodrug</u>. Deeper administered prodrugs (i.e. intramuscular injections) are suggested to be absorbed via a longer path, but at a higher flow, which results in a longer lag time but a higher absorption rate constant of the prodrug.</em></strong></p><p><strong><em>[ATTACH=full]15100[/ATTACH]</em></strong></p><p><strong>Figure 7.2: <u>Schematic overview of the new insights into drug absorption from oil depots</u>. After release from the oil depot (yellow circle at the injection site), the prodrug is transferred towards the central compartment via the lymphatic system. Here, it will be hydrolyzed to the active substance (see circle). ka = absorption rate constant; ke = elimination rate constant.</strong></p><p><strong></strong></p><p><strong></strong></p><p><strong></strong></p><p><strong></strong></p><p><strong></strong></p><p><strong></strong></p><p><strong></strong></p><p><strong></strong></p><p><strong>Formulation </strong></p><p></p><p><em>XYOSTED is an SC drug/medical device combination product. Each single-use prefilled XYOSTED auto-injector contains <strong><em>sterile, <u>preservative-free</u> TE in nonpyrogenic clear colorless to yellow solution</em></strong> for SC administration of a fixed volume of 0.5 mL yielding final delivered doses of 50 mg, 75 mg, or 100 mg TE. TE is contained within a single-dose syringe with a 27-gauge, ½-inch needle with a soft needle shield within an auto-injector, which is equipped with a needle safety guard and safety cap. Each XYOSTED device provided a single dose as a single injection.</em></p><p></p><p></p><p>XYOSTED (testosterone enanthate) is supplied as an auto-injector device intended for SC injection.</p><p></p><p>Xyosted is preservative-free.</p><p></p><p>I use big pharma Delatestryl (testosterone enanthate) and the only difference, when compared to Xyosted, is that it has <u>0.5% chlorobutanol as a preservative</u>. It is available in glass vials containing 5 mL, sealed with latex-free stoppers.</p><p></p><p>Regarding half-lives keep in mind that a majority of studies on the PK/PD of the various T-esters were done using <u>IM (once weekly/fortnightly) injections</u> in a small number of subjects and most of the literature is from decades ago.</p><p></p><p>There are many other factors that affect the rate at which the testosterone is released from the oily depot at the injection site.</p><p></p><p>Sub-q vs IM, the volume of injection, injection depth, site of injection, lymphatic flow,<strong><em> the concentration of BOH (benzyl alcohol) are other possible factors that can affect absorption rates of the esterified hormone.</em></strong></p><p></p><p>I have stated in the past that BOH apparently causes a large bolus of the prodrug to be released earlier which was discussed in this paper that I posted in a thread from 2018.</p><p></p><p><strong><em>*It is demonstrated in this dissertation that there is a role of the excipient BOH in yielding an initially high absorption.</em></strong></p><p></p><p>I know there are even nandrolone studies showing that the addition of BOH (benzyl alcohol) which is commonly used in many injectable preparations has been shown to cause two distinct peaks.....one early and another days later as the BOH apparently causes a large bolus of the prodrug to be released early.</p><p></p><p>Benzyl alcohol (BOH) is a commonly used excipient in oil depots in concentrations ranging from 1.5-10% v/v and is used as a</p><p></p><p><em><strong>*solubility enhancer</strong></em></p><p><em><strong>*oil viscosity reducer</strong></em></p><p><strong><em>*local anesthetic</em></strong></p></blockquote><p></p>
[QUOTE="madman, post: 203291, member: 13851"] [B]Fundamental understanding of drug absorption from a parenteral oil depot (2016) CONCLUSIONS[/B] It is interesting to realize that drug absorption from an oil depot cannot entirely be described by a simple two-phase mass transfer model where concentration gradients, diffusion, and partition coefficients would enable the calculation of the expected absorption.[B][I] It is demonstrated in this dissertation that there is a role of the excipient BOH in yielding an initially high absorption. [/I][/B]The oil depot forms a continuous phase after injection but will be dispersed and encapsulated at the injection site after some days. [B][I]This in turn largely influences the way the prodrug becomes available; after release from the oil depot,[/I][/B] it is present in the interstitial fluid which is drained through the lymph into the systemic circulation. Subsequently, the prodrug permeates through the wall of blood cells and is hydrolyzed. Both the lymph transport and the cell wall permeation take time which is expressed in a lag time. [B][I]This lag time is different for each injection site: [U]a subcutaneously administered prodrug will enter the systemic circulation via a short path and at a low drainage flow[/U]. [U]This results in a short lag time and a slow absorption rate constant of the prodrug[/U]. Deeper administered prodrugs (i.e. intramuscular injections) are suggested to be absorbed via a longer path, but at a higher flow, which results in a longer lag time but a higher absorption rate constant of the prodrug. [ATTACH type="full" alt="Screenshot (5595).png"]15100[/ATTACH][/I] Figure 7.2: [U]Schematic overview of the new insights into drug absorption from oil depots[/U]. After release from the oil depot (yellow circle at the injection site), the prodrug is transferred towards the central compartment via the lymphatic system. Here, it will be hydrolyzed to the active substance (see circle). ka = absorption rate constant; ke = elimination rate constant. Formulation [/B] [I]XYOSTED is an SC drug/medical device combination product. Each single-use prefilled XYOSTED auto-injector contains [B][I]sterile, [U]preservative-free[/U] TE in nonpyrogenic clear colorless to yellow solution[/I][/B] for SC administration of a fixed volume of 0.5 mL yielding final delivered doses of 50 mg, 75 mg, or 100 mg TE. TE is contained within a single-dose syringe with a 27-gauge, ½-inch needle with a soft needle shield within an auto-injector, which is equipped with a needle safety guard and safety cap. Each XYOSTED device provided a single dose as a single injection.[/I] XYOSTED (testosterone enanthate) is supplied as an auto-injector device intended for SC injection. Xyosted is preservative-free. I use big pharma Delatestryl (testosterone enanthate) and the only difference, when compared to Xyosted, is that it has [U]0.5% chlorobutanol as a preservative[/U]. It is available in glass vials containing 5 mL, sealed with latex-free stoppers. Regarding half-lives keep in mind that a majority of studies on the PK/PD of the various T-esters were done using [U]IM (once weekly/fortnightly) injections[/U] in a small number of subjects and most of the literature is from decades ago. 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,[B][I] the concentration of BOH (benzyl alcohol) are other possible factors that can affect absorption rates of the esterified hormone.[/I][/B] I have stated in the past that BOH apparently causes a large bolus of the prodrug to be released earlier which was discussed in this paper that I posted in a thread from 2018. [B][I]*It is demonstrated in this dissertation that there is a role of the excipient BOH in yielding an initially high absorption.[/I][/B] I know there are even nandrolone studies showing that the addition of BOH (benzyl alcohol) which is commonly used in many injectable preparations has been shown to cause two distinct peaks.....one early and another days later as the BOH apparently causes a large bolus of the prodrug to be released early. Benzyl alcohol (BOH) is a commonly used excipient in oil depots in concentrations ranging from 1.5-10% v/v and is used as a [I][B]*solubility enhancer *oil viscosity reducer[/B][/I] [B][I]*local anesthetic[/I][/B] [/QUOTE]
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