1. An adaptive control system for administering a drug to a subject responsive to a drug/subject system model, comprising: (a) means for sensing at least one physiological parameter of said subject and for converting said at least one parameter into a corresponding response signal; (b) preset means for establishing a preset drug order signal; (c) means for administering said drug to said subject in response to an actuating signal; and (d) a control loop for providing said actuating signal to said means for administering, said control loop including: (i) comparator means for accepting first and second input signals and producing an error signal representing the difference therebetween, said comparator means being connected to said preset means for accepting said order signal as a first input thereto; (ii) response signal processing means connected to said sensing means for processing said response signal and for providing said processed response signal as a second input of said comparator means; (iii) means for sampling said response signals and rates at which drugs are administered by said means for administering; (iv) means for determining values for said drug/subject system model as a function of said sampled signals and rates and producing control signal information in accordance therewith; (v) adaptive controller means for receiving said error signal from said comparator means and said control signal information from said means for determining, said adaptive controller means translating said error signal into an actuating signal for application to said administering means in accordance with said values for said drug/subject system model defined by said control signal to optimally minimize said error signal.