The objective of this analysis of a linear compartment system is to compute drug input functions that are optimal in producing nontoxic pharmacological responses of maximal therapeutic efficacy. Pharmacokinetics should underlie the rational use of drugs and when a therapeutic range is known, the achievement of safe and effective target concentrations may be assured by a dosage regimen computed for a given administration schedule. The method developed herein is based on linearity and superimposition principles applicable to the class of systems considered. This method requires estimated values of model individual parameters and computes optimum dosage regimens in an iterative scheme, corresponding to a real time dynamical context. An interactive computer program has been developed to perform dosage regimen calculations.