The Peptide CommonsEst. May 2024
Independent. We sell nothing and are affiliated with no manufacturer or pharmacy. Every moderation action is logged in public
Pharmacology · Pharmacokinetics · continued

Half-life, steady state, and accumulation worked through posts 121–131

This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.

MI
m.ibarraTL215 Jun 2025#121
MH
ms_hollowayTL4Mass spectrometrist15 Jun 2025#122

Hepatic metabolism: the degree to which each compound is hepatically metabolised versus renally cleared is known but varies. Severe liver disease changes clearance.

0 likes 13mo
MB
m.brobergTL2 Moderator15 Jun 2025#123

post #122 answers the question as asked. The question underneath it is different.

Bioavailability: oral semaglutide has low bioavailability (roughly 1%) due to peptide instability. That is why the oral dose (14 mg) is so much larger than the injectable dose. Comparing them by mass is meaningless.

1 like 13mo
SL
s.leclercTL4 Moderator16 Jun 2025#124
logbook_erin, post #11: post #10 answers the question as asked. The question underneath it is different. Accumulation at steady state: with a week-long half-life, steady-state concentration is reached around 4 to 5 half-lives (about 4 to 5 weeks). Before that, concentration is rising with each dose. The clinical implication: escalating before 4 weeks means… Go to post

SNAC (the oral bioavailability enhancer): sodium N-(8-[2-hydroxybenzoyl]amino) caprylate transiently raises gastric pH and promotes absorption. Without it, oral bioavailability is too low for clinical use. With it, bioavailability is still variable between people.

7 likes in reply to #11 13mo
JS
j.steinerTL2 Moderator16 Jun 2025#125

Accumulation at steady state: with a week-long half-life, steady-state concentration is reached around 4 to 5 half-lives (about 4 to 5 weeks). Before that, concentration is rising with each dose. The clinical implication: escalating before 4 weeks means escalating before steady state.

12 likes 13mo
AR
a.reyesTL4 Admin16 Jun 2025 · edited#126
Staff post. Actions described here are recorded in the public moderation log and may be challenged in Meta.

I read post #124 twice before replying, because I had assumed the opposite.

Two things before anyone answers the substance.

First, the context in the first post is clear and specific. Second, the question is framed so that an answer can actually address it. Both are the norm here and both matter more than they sound.

26 likes 13mo
PM
p.mbekiTL2 Moderator16 Jun 2025#127

Individual variation: people vary in how quickly they absorb, distribute, metabolise, and excrete these compounds. That variation is partly genetic and partly due to individual biology (gut motility, kidney and liver function). It explains why two people on the same dose have different response magnitudes.

0 likes 13mo
NM
n.moreauTL2 Moderator16 Jun 2025#128
r.venkatesan, post #24: This follows post #21 rather than contradicting it. Volume of distribution: the theoretical volume the drug distributes into. For albumin-binding compounds, volume is reduced compared to drugs that do not bind protein. That is relevant to understanding how much free drug is available. Go to post

Half-life: semaglutide ≈ 165–184 hours (about a week). Tirzepatide ≈ 5 days. Liraglutide ≈ 13 hours. The half-life determines how much accumulation happens at steady state and how long it takes to clear after stopping.

4 likes in reply to #24 13mo
TN
t.ndiayeTL2 Moderator17 Jun 2025#129
isotonic_sheet, post #26: Hepatic metabolism: the degree to which each compound is hepatically metabolised versus renally cleared is known but varies. Severe liver disease changes clearance. Go to post

Picking up post #126: that is the part I would want checked first.

Fasting requirement for oral semaglutide: food and large fluid volumes reduce absorption. The fasting window (30 minutes before and 30 minutes after) is designed to maximise absorption. Violating it measurably reduces exposure.

8 likes in reply to #26 13mo
AF
a.friskTL2 Moderator17 Jun 2025#130
ambient_review, post #55: post #54 answers the question as asked. The question underneath it is different. Individual variation: people vary in how quickly they absorb, distribute, metabolise, and excrete these compounds. That variation is partly genetic and partly due to individual biology (gut motility, kidney and liver function). It explains why two people on… Go to post

Renal clearance: these compounds are cleared partly via the kidney. In severe renal impairment, clearance is slowed and accumulation risk is higher. Dose adjustments might be needed.

19 likes in reply to #55 13mo
GO
g.oyelaranTL2 Moderator17 Jun 2025#131

Practical note that does not fit anywhere else. Whatever you conclude from this topic, write down what you did and when. The single most useful thing in your own records is not any individual result; it is that they are dated and consecutive.

11 likes 13mo

Suggested topics

TopicParticipantsRepliesViewsActivity
Follow-up: Subcutaneous absorption kinetics and site differences
Subcutaneous absorption kinetics and site differences — setting out what I have, and where I think it stops being reliable. I would like to understand what this number means before I repeat it anywhere. A…
HCFPNVBICM 4 9.9k 10mo
Clearance pathways and what renal impairment changes
Clearance pathways and what renal impairment changes Writing it up because I had to work it out twice and would rather nobody else did. I would like to understand what this number means before I repeat it…
BAWADAKLS+11 15 43k 2mo
Peak-to-trough ratio at steady state for a weekly agent — the long version
Peak-to-trough ratio at steady state for a weekly agent — the long version Writing it up because I had to work it out twice and would rather nobody else did. I would like to understand what this number means…
CTRSWAVUC+57 61 708 1d
Time to steady state after a dose increase
On the subject in the title: Time to steady state after a dose increase Working notes rather than a conclusion. A documentation question rather than an analytical one. I have a certificate in front of me that…
LCKJSLKC+151 163 9.7k 21mo
[2026 update] Clearance pathways and what renal impairment changes
On the subject in the title: Clearance pathways and what renal impairment changes Working notes rather than a conclusion. A documentation question rather than an analytical one. I have a certificate in front…
CWFTADMHSA+63 69 50k 13mo

Related topics — sharing the tags semaglutide, liraglutide, tirzepatide

TopicParticipantsRepliesViewsActivity
Albumin binding and how it produces a long half-life
Albumin binding and how it produces a long half-life — setting out what I have, and where I think it stops being reliable. I would like to understand what this number means before I repeat it anywhere. A…
SDDMTBBTAM+38 44 6.6k 14mo
Revisiting: GLP-1 receptor distribution: central and peripheral
Revisiting: GLP-1 receptor distribution: central and peripheral — setting out what I have, and where I think it stops being reliable. A documentation question rather than an analytical one. I have a…
RTHFDTIBRM+61 66 15k 8mo
Tirzepatide in type 2 diabetes: the SURPASS programme, summarised honestly — the long version
On the subject in the title: Tirzepatide in type 2 diabetes: the SURPASS programme, summarised honestly — the long version Working notes rather than a conclusion. Session topic: PIONEER 6 ( N Engl J Med ,…
SCCHOLNVKB+85 90 13k 7mo
Coming back to: Time to steady state after a dose increase
Time to steady state after a dose increase Writing it up because I had to work it out twice and would rather nobody else did. Posting the method first, because I know what the first three replies will…
MSPMAICLAP+104 110 16k 2d
Titrating on tolerability rather than on the calendar
On the subject in the title: Titrating on tolerability rather than on the calendar Working notes rather than a conclusion. I have read the maintained page on this and I still have a gap, so I am asking rather…
POCCMH 2 31k 13mo