Fig. 9. Combination of the optimal concentrations range with the effect compartment concentrations profile after the bolus administration of 1.5 mg of drug A and 1.5 mg of drug B. The optimal concentrations range is shown for varying values of the interaction parameter between the positive effects (β). The points corresponding to t = 8 and t = 11 indicate how many minutes after the bolus the concentrations profile enters the optimal range for β= 2, β  ^N = 0 and for β= 0, β  ^N = 0, respectively.