Topic summary

Washout: how long is long enough, and for what purpose

Pharmacology › Pharmacokinetics semaglutide missed dose worked example Closed

This is a generated summary. It shows the 9 most-liked posts from a topic of 71, in their original order, with the accepted answer included where one exists. It is a reading aid and it will miss nuance — the full topic is the record.

bench_notesTL4 Moderator1 Feb 2025#2

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

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.

23 likes 18mo

r.erdoganTL2 Moderator19 Feb 2025#5

batchlog, post #1: Washout: how long is long enough, and for what purpose — setting out what I have, and where I think it stops being reliable. A documentation question rather than an analytical one. I have a certificate in front of me that reports a purity figure, names a technique, gives a wavelength, and stops. No gradient, no column, no injection… 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.

32 likes in reply to #1 17mo

z.onwukaTL2 Moderator31 Mar 2025#14

i.amankwah, post #10: 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. Go to post

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.

28 likes in reply to #10 16mo

a.silvaTL2 Moderator3 May 2025#23

lc_gradient, post #6: 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. Go to post

On post #19 — agreed on the reasoning, with one qualification.

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.

33 likes in reply to #6 15mo

h.karlsenTL2 Moderator21 May 2025#28

a.batista, post #4: Thank you for the correction. I have edited my earlier post with a note rather than silently, so the thread still makes sense to read. The error was mine and it was the kind that comes from remembering a figure instead of looking it up. Go to post

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

24 likes in reply to #4 14mo

IMainwaringTL3Regular3 Jun 2025#32

bench_notes, post #2: Picking up the opening post: that is the part I would want checked first. 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. Go to post

Worth separating two things that post #28 runs together.

25 likes in reply to #2 14mo

m.ibarraTL2 Moderator26 Jun 2025#39

o.cousineau, post #24: 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

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

24 likes in reply to #24 13mo

chromatogramTL4Analytical chemist11 Jul 2025 · edited#44

This follows post #41 rather than contradicting it.

I disagree with the reply above, and I think the disagreement is substantive rather than terminological.

The distinction being drawn does not survive when you look at the published data for this specific question. I would be glad to be shown wrong on this, because the version I am arguing against is more convenient.

26 likes 13mo

n.laurentTL2 Moderator2 Sep 2025 · edited#62

I disagree with the reply above, and I think the disagreement is substantive rather than terminological.

31 likes 11mo

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Half-life, steady state, and accumulation worked throughPharmacology › Pharmacokinetics · 130 replies

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