Effect-Compartment PK/PD Hysteresis Simulator (2D)

A drug's plasma concentration and its clinical effect are not the same curve. This 2D simulator models the classic effect-compartment ("biophase") link between a one-compartment plasma pharmacokinetic model and a sigmoid Emax pharmacodynamic response, rendering it as a physical two-tank diffusion analogy: drug molecules stream through a connecting channel from the plasma tank into the effect-site tank at a rate set by the instantaneous concentration gradient, while a live strip chart and a dedicated hysteresis-loop panel plot the resulting concentration and effect curves directly. Adjust the peak plasma concentration, elimination half-life, effect-site equilibration rate (k_e0) and EC₅₀ to see how a fast-equilibrating drug tracks plasma almost immediately while a slow one produces a wide, sluggish loop — the same mechanism that explains why a sedative or analgesic's peak effect always trails its peak blood level.