Steady State
Also known as: steady-state concentration · Css
The point at which the rate of peptide administration equals the rate of elimination, producing a stable average plasma concentration.
Steady state is conventionally reached after 4–5 half-lives of consistent dosing. Before steady state, researchers are still building up tissue exposure; after steady state, they've achieved predictable peak/trough cycling. This is why most protocols include a 'loading phase' — the first weeks of a long-half-life peptide protocol are mathematically pre-steady-state and don't reflect the compound's stabilized pharmacology.
Judging a compound's effect before steady state is the single most common protocol analysis error. A researcher deciding Tirzepatide 'doesn't work' after two doses is comparing to a concentration that is roughly 30% of what they'll see at steady state in week 5.
Related Terms
Half-Life
The time required for the concentration of a peptide in the body to fall to half of its peak value.
Loading Phase
The initial period of a protocol during which elevated or frequent dosing rapidly builds tissue exposure to a target level.
Cmin
The lowest plasma concentration of a peptide during a dosing interval, typically measured immediately before the next dose.
Cmax
The maximum plasma concentration reached after a single dose of a peptide.
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