Figure 12-24 Schematic illustration of pharmacokinetic model-driven drug delivery. The physician enters the target plasma or biophase drug concentration (Cp_d ). An infusion device control algorithm uses a pharmacokinetic model for the drug being infused to determine what the infusion rate should be for the next infusion interval (e.g., 9 to 15 seconds). The infusion device delivers drug to the patient, and the infusion rate is fed into a simulation of the pharmacokinetic model to compute the current predicted plasma drug concentration (Cp_p ). The variables computed in the simulation are available to the infusion algorithm, which then calculates the infusion rate necessary for the next 9 to 15 seconds to achieve the target concentration. On the basis of monitored and anticipated patient response, knowledge of approximate therapeutic plasma drug concentrations (e.g., Cp₅₀ ), and Cp_p , the physician can titrate Cp_d as necessary.