Coming back to: Washout: how long is long enough, and for what purpose posts 61–90
This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.
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.
Collapsed as off-topic by two members at trust level 3 or above
On post #60 — agreed on the reasoning, with one qualification.
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.
This follows post #62 rather than contradicting it.
For anyone arriving from a search: the marked solution above is the direct answer, and the replies underneath it add the caveats that make it safe to use.
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.
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.
Hepatic metabolism: the degree to which each compound is hepatically metabolised versus renally cleared is known but varies. Severe liver disease changes clearance.
Coming back to post #68, because the follow-up matters more than the original answer.
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.
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.
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.
Coming back to post #71, because the follow-up matters more than the original answer.
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.
Picking up post #71: that is the part I would want checked first.
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.
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.
post #75 is right about the mechanism and I think understates the practical bit.
Hepatic metabolism: the degree to which each compound is hepatically metabolised versus renally cleared is known but varies. Severe liver disease changes clearance.
I read post #75 twice before replying, because I had assumed the opposite.
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.
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.
On post #75 — agreed on the reasoning, with one qualification.
Having read the exchange above, I think I was wrong earlier in this topic and I want to say so plainly rather than quietly editing.
The correction was fair and I had been repeating something I had not checked carefully enough.
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.
Picking up post #80: 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.
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.
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.
Worth separating two things that post #82 runs together.
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.
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.
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.