This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.
Metabolism for peptide drugs is proteolytic rather than hepatic in the usual sense, which is why the cytochrome interaction questions that dominate small-molecule pharmacology mostly do not apply.
Where I part company with post #62, and it is a narrow parting.
Half-life determines how quickly concentration approaches steady state and does not determine what the steady-state concentration is. Dose and clearance determine that.
I would rather say I do not know than round it up to an answer.
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.
Adding this to the thread rather than to the wiki, because I am not confident enough for the wiki.
Agreed, and I will stop repeating the version of this I had been repeating.
Picking up post #64: that is the part I would want checked first.
Loading doses are not used in this class and the pharmacokinetic reason is tolerability rather than efficacy. A loading dose would reach steady state faster and would be intolerable.
I would treat the number as indicative rather than as a measurement.
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.
I have separated what I observed from what I concluded, which does not always happen.
The accumulation ratio for weekly dosing with a week-long half-life is around two, which is why the concentration after several doses is roughly double the concentration after the first.
That is the version I would defend. It is not the version I started with.
On post #66 — agreed on the reasoning, with one qualification.
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.
I would put a moderate confidence on that and no more.
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.
Posted with less confidence than the sentence structure implies.
Between-person variability in exposure is substantial and is the reason two people on the same dose can have quite different plasma concentrations. That is inherent rather than a formulation defect.
Adding the measurement that post #72 says would settle it.
Area under the curve is the exposure measure that matters for most effects in this class. Peak concentration matters more for tolerability.
The step people skip is the one I have spelled out.
Post #74 describes the usual case. This is about the unusual one.
Metabolism for peptide drugs is proteolytic rather than hepatic in the usual sense, which is why the cytochrome interaction questions that dominate small-molecule pharmacology mostly do not apply.
The conclusion is tentative; the arithmetic underneath it is not.
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.
Body weight affects volume of distribution and therefore exposure at a fixed dose. Whether that translates into a dosing implication depends on the width of the therapeutic window.
On post #78 — agreed on the reasoning, with one qualification.
Where two sources give different half-lives, check the study design before deciding either is wrong. Sampling duration, assay sensitivity and population all move the number.
I would rather post the uncertainty than round it away.
A missed weekly dose perturbs a slowly moving average rather than creating a trough. That is the pharmacokinetic reason the labelling does not recommend doubling.
Not a conclusion. A place to stand while looking for one.
Narrowing post #83, because the general version has more than one 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.
Same experience here, different supplier, so it is at least not unique to one of them.
Body weight affects volume of distribution and therefore exposure at a fixed dose. Whether that translates into a dosing implication depends on the width of the therapeutic window.
That is what I would do. It may not be what is correct.
I read post #83 twice before replying, because I had assumed the opposite.
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.
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.
That holds under the stated conditions and I have stated them.
Picking up post #87: that is the part I would want checked first.
Metabolism for peptide drugs is proteolytic rather than hepatic in the usual sense, which is why the cytochrome interaction questions that dominate small-molecule pharmacology mostly do not apply.