Drug concentration models
Drug concentration models represent dosing together with absorption, distribution and elimination.
Constant intravenous infusion
For concentration \(C(t)\), infusion rate \(R\), volume \(V\) and elimination rate \(k\),
\[\frac{dC}{dt}=\frac{R}{V}-kC.\]The steady concentration is
\[C^*=\frac{R}{kV}.\]Repeated doses
Repeated administration can produce peaks and troughs. Their size depends on dose, dosing interval and elimination rate. Multi-compartment models can represent rapid distribution followed by slower elimination.
Key idea. Drug concentration is dynamic: treatment schedules create time-varying exposure rather than a single fixed dose level.