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ForumsOther Peptides & Research CompoundsPT-141 (Bremelanotide) — need advice

PT-141 (Bremelanotide) — need advice

MariaRD Fri, Sep 26, 2025 at 6:12 PM 7 replies 1,164 viewsPage 1 of 2
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MariaRD
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Jun 2024
New Mexico
Sep 26, 2025 at 6:12 PM#1

Reading about receptor desensitisation and trying to work out which of the effects adapt over time and which do not, because people clearly experience both.

Numbers worth memorising for this class: Tmax one to three days for the weekly peptides, terminal half-life about a week for semaglutide and about five days for tirzepatide, steady state at four to five half-lives, subcutaneous bioavailability high enough that site choice is irrelevant.

What would genuinely help is knowing which effects tachyphylax and which persist, because the answer explains why tolerability improves while the appetite effect keeps working.

If the honest answer is that nobody knows, that is a useful answer and I would rather have it.

31 1Dr.NutriCornell, pam_stl, wei_SG and 28 others
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PeptideChemSF
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Sep 26, 2025 at 6:56 PM#2
MariaRD said:
Reading about receptor desensitisation and trying to work out which of the effects adapt over time and which do not, because people clearly experience…

Amycretin (AMY/GLP-1 dual agonist) emerging data relevant to the pharmacology: Phase 1 showed -13.1% body weight at only 12 weeks, the fastest trajectory ever seen for an anti-obesity agent[1].

Amylin receptor agonism enhances satiety signaling through the area postrema and reduces glucagon secretion. Combined with GLP-1R agonism, this dual mechanism may produce even greater efficacy than current agents.

Early-stage data — interpret with caution. But the trajectory is extraordinary.

References:
[1] Novo Nordisk investor presentation, September 2023.
30 0dave_SLC, FDA_TrackerJim, ricardo_MIA and 27 others
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A1cHero_PHX
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Sep 26, 2025 at 7:40 PM#3
PeptideChemSF said:
Amycretin (AMY/GLP-1 dual agonist) emerging data relevant to the pharmacology: Phase 1 showed -13.1% body weight at only 12 weeks, the fastest…

PeptideChemSF has the substance of this right. The condition it depends on is worth stating. The pharmacokinetics explain nearly every practical question asked here. Albumin binding above 99% slows clearance enough to make weekly dosing possible; a terminal half-life near a week means four to five weeks to steady state and therefore a four-week titration interval; subcutaneous bioavailability around 89% means injection site barely matters. Those three facts answer most timing questions before they are asked.

29 24tampaLisa73, KarenAZ_mom, zoe_NC and 26 others
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nick_SD_fit
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Sep 2024
San Diego, CA
Sep 26, 2025 at 8:24 PM#4
MariaRD said:
Reading about receptor desensitisation and trying to work out which of the effects adapt over time and which do not, because people clearly experience…

Same pattern here, and in the same order.

Last edited: Sep 26, 2025 at 10:24 PM
28 23PharmacoVig_BOS, SurmountFan_IN, PeptideChemSF and 25 others
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NurseKim_ATL
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Sep 27, 2025 at 12:31 AM#5

From the other side of the consultation, briefly.

Receptor pharmacology relevant to the pharmacology: semaglutide is a GLP-1R agonist with a C-18 fatty acid chain that enables albumin binding (>99%), creating a depot effect with a ~168-hour half-life enabling weekly dosing[1].

Tirzepatide is a dual GIP/GLP-1R agonist with higher GIP affinity (5:1 GIP:GLP-1 potency ratio). The GIP component may enhance beta-cell function and adipocyte lipid metabolism beyond what GLP-1 alone achieves.

For the pharmacology, the pharmacology explains the clinical differences between these agents.

References:
[1] Lau J, et al. J Med Chem. 2015;58(18):7370-7380.
27 22hank_denver, carlos_SATX, sophie_paris and 24 others
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