Rapid compartment- and model-independent estimation of times required to attain various fractions of steady-state plasma level during multiple dosing of drugs obeying superposition principle and having various absorption or infusion kinetics.

A new general equation based only on plasma data was derived for rapid estimation of the average plasma level and the mean fraction of the steady-state plasma level attained during any multiple-dosing interval. It can be applied to any complex absorption or infusion kinetics (i.e., is not limited to zero-order or first-order kinetics) for drugs obeying linear disposition kinetic or superposition principles. The time, t, required to reach a certain mean fraction of the steady-state plasma level is equal to the time at which the plasma area from time zero to time t is equal to the same fraction of the plasma area from time zero to infinity (AUC0 leads to infinity) following a single dose. No other pharmacokinetic parameters are necessary.