AUCintravenous

AUC intravenous, or the area under the curve following intravenous administration, refers to the integral of the plasma concentration–time curve after an IV dose. It represents total systemic exposure to the drug over time and is a central pharmacokinetic parameter.

In linear pharmacokinetics with complete bioavailability (F = 1) after an IV dose, AUC_iv equals Dose divided by clearance (AUC_iv = Dose / CL). For a bolus dose, the initial plasma concentration is Dose divided by the volume of distribution (C0 = Dose / Vd), and the elimination half-life is t1/2 = 0.693 × Vd / CL. AUC is the integral of Cp(t) from time zero to infinity. AUC_iv can be estimated from experimental plasma concentration data using noncompartmental analysis or from fitted compartment models; common numerical methods include the trapezoidal rule.

AUC_iv is used to characterize drug exposure, compare bioavailability between routes, and estimate clearance. It supports dose optimization and adjustments in organ impairment or in the presence of drug interactions. The parameter is also employed in bioequivalence studies and in therapeutic drug monitoring for drugs with narrow therapeutic indices when intravenous administration is involved.

Limitations include potential nonlinearity at high doses, variability in protein binding, timing of sample collection, and assay error. In nonlinear pharmacokinetics, AUC_iv may not scale proportionally with dose, and parameter estimates from linear models may be unreliable.