Fig. 6.

Multiple compartment indirect response models (top panel) and signature profiles for Models V and VI (bottom panel). Response curves were simulated using Eqs. 11 and 12 driven by drug concentrations following monoexponential disposition: C_p = C^oe^(−kt). C^o was set to 10, 100, or 1,000 units to achieve increasing doses. Parameter values were k = 0.12/h, I_max = 1 unit, S_max = 10 units, EC₅₀ = 15 units, k_o = 25 unit/h, k_p = 0.5/h, and k_out = 0.25/h.