Loading Dose
An initial higher dose of a drug given to rapidly achieve therapeutic blood levels, followed by lower maintenance doses. Loading doses are used when the drug has a long half-life and waiting for steady state through regular dosing alone would delay therapeutic effect.
Technical Context
Loading dose = target Css × Vd / F, where Css is the desired steady-state concentration, Vd is volume of distribution, and F is bioavailability. Loading doses are useful when the half-life is long enough that reaching steady state through maintenance dosing alone would take an unacceptably long time (remember: steady state requires ~4-5 half-lives). For a drug with a 1-week half-life, steady state takes ~4-5 weeks with regular dosing. Loading doses are more commonly used for small molecule drugs (e.g. amiodarone) and some antibiotics. For GLP-1 RAs, the dose titration approach (starting low, escalating gradually) serves a different purpose than loading — it's about tolerability, not speed to steady state.