Steady State
The condition reached during repeated drug dosing when the rate of drug administration equals the rate of drug elimination, resulting in a stable average drug concentration. Steady state is typically achieved after 4-5 half-lives of regular dosing and is the basis for therapeutic drug level monitoring.
Technical Context
At steady state, plasma concentrations fluctuate between Cmax (peak after each dose) and Ctrough (just before the next dose) around a mean steady-state concentration (Css). For drugs with short half-lives relative to the dosing interval, these fluctuations are large. For drugs with long half-lives (like weekly semaglutide), fluctuations are minimal, providing relatively constant drug exposure. Time to reach steady state depends only on half-life (approximately 4-5 × t1/2), not on dose. Loading doses can achieve near-steady-state concentrations immediately. Dose titration schedules for GLP-1 RAs ensure that steady-state concentrations are reached gradually at each dose level, allowing adaptation to side effects.