Simplified method for estimating volume of distribution at steady state.

Current methods for measuring the volume of distribution at steady state (Vdss) require extrapolation of the plasma concentration curve from time zero to infinity (AUC0-infinity). A new method for measuring Vdss is described. This method saves time since it requires following the plasma concentration curve only until a steady state is reached. The Vdss of sulfamethizole was measured simultaneously by the new method (2 hr) and by established methods (7 hr) in six dogs. There was not significant difference between the results obtained by the two methods.