Midpoint back-extrapolation method for the rapid estimation of drugs' volume of distribution and dosage adjustment exhibiting multicompartmental characteristics.

A midpoint back-extrapolation method assuming an instantaneous drug input at the midpoint of intravenous infusion based on a linear one-compartment open model is used to estimate the apparent volume of distribution and total body clearance of drugs exhibiting multicompartmental characteristics. Error analyses indicate that the method is clinically satisfactory for drugs not showing a strong multicompartmental property. For drugs exhibiting extensive multicompartmental properties, proper corrections based on the average literature data can be made. This method requires only two to three blood samples for the estimation of clinically useful pharmacokinetic parameters.