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ForumsOral GLP-1 AgonistsOral vs injectable GLP-1: bioavailability and efficacy comparison — anyone have experience? Page 2

Oral vs injectable GLP-1: bioavailability and efficacy comparison — anyone have experience?

stefan_berlin Tue, Nov 18, 2025 at 5:28 PM 45 replies 2,165 viewsPage 2 of 9
Dr.RaviCardio
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Nov 18, 2025 at 6:59 PM#6
Dr.GutHealth said:
Receptor pharmacology relevant to the pharmacology: semaglutide is a GLP-1R agonist with a C-18 fatty acid chain that enables albumin binding (>99%),…

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.
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lisa_labSD
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Nov 18, 2025 at 7:34 PM#7
stefan_berlin 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…

Semaglutide structural biology relevant to the pharmacology: semaglutide is a 31-amino acid peptide with 94% homology to native GLP-1(7-36). Three key modifications enable its pharmacokinetic profile:

  1. Aib8 substitution: DPP-4 resistance (prevents enzymatic degradation)
  2. Arg34 substitution: improved chemical stability
  3. C18 fatty diacid at Lys26: albumin binding → long half-life

These three modifications transform a peptide with a 2-minute half-life (native GLP-1) into one with a 168-hour half-life (semaglutide). A masterclass in peptide engineering.

Last edited: Nov 18, 2025 at 10:34 PM
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Dr.ObesityMed
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Nov 18, 2025 at 8:09 PM#8
Dr.RaviCardio 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…

Pharmacist here. I want to add the drug interaction perspective on the pharmacology.

Key points from a pharmacokinetic standpoint:

  • GLP-1 agonists delay gastric emptying, which can affect Tmax of co-administered oral medications
  • Monitor patients on warfarin (INR), levothyroxine (TSH), and oral contraceptives during dose titration
  • The albumin-binding mechanism of semaglutide (C-18 fatty acid linker) gives it the ~168-hour half-life that enables weekly dosing
  • Steady state is reached at approximately 4-5 weeks after dose initiation or adjustment

Re: the pharmacology specifically — the pharmacology here is well-characterized and the clinical implications are straightforward.

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sophie_paris
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Nov 18, 2025 at 8:44 PM#9

A narrower follow-up, since the general answer is now clear:

Did your prescriber agree with that reading, and if not what was their objection?

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stefan_berlin
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Nov 18, 2025 at 11:33 PM#10

Reporting back.

Closing this out: the trough rather than the peak explains the pattern I was seeing on day six, which I had been blaming on the vial.

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