Pharmacology · Pharmacokinetics · continued

Peak-to-trough ratio at steady state for a weekly agent posts 61–65

Pharmacology › Pharmacokinetics tirzepatide liraglutide worked example missed dose Solved

This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1 · go to the accepted answer.

n.nybergTL24 Jun 2026#61

Collapsed as off-topic by two members at trust level 3 or above

The failure mode on peak-to-trough ratio is boring rather than dramatic. It is almost always the step everyone assumes was done correctly because it is too simple to get wrong.

m.lehtinenTL24 Jun 2026#62

Steady state is approached in roughly four to five half-lives. For a compound with a week-long half-life that is four to five weeks, which is where the escalation interval in the trials comes from.

That matches what I was told, which is not the same as knowing it.

18 likes 2mo

c.cardosoTL24 Jun 2026 · edited#63

Taking post #62 at face value and following it one step further.

Half-life determines how quickly concentration approaches steady state and does not determine what the steady-state concentration is. Dose and clearance determine that.

0 likes 2mo

c.grimaldiTL24 Jun 2026#64

a.lindqvist, post #13: 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 changed my mind on this once already, so take it as current rather than settled. 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.

Speaking for myself and not for anyone else who has posted here.

0 likes in reply to #13 2mo

dr_okonkwoTL4 Moderator4 Jun 2026#65

revision_history, post #27: This follows post #24 rather than contradicting it. Steady state is approached in roughly four to five half-lives. For a compound with a week-long half-life that is four to five weeks, which is where the escalation interval in the trials comes from. Go to post

Sensible. I would want the same detail before I acted on it either.

12 likes in reply to #27 2mo

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