Fig. 1. Schematic representation of the pharmacokinetic–pharmacodynamic (PK-PD) interaction model for rocuronium and sugammadex. (  A ) PK model for rocuronium alone; (  B ) PK-PD model for rocuronium alone; (  C ) PK interaction model; (  D ) PK-PD interaction model;  Cl^roc = rocuronium clearance;  Cl^sug = sugammadex clearance;  EC⁵⁰ = concentration at 50% of maximum effect;  E^max = maximum effect;  K¹ = association rate constant;  K² = dissociation rate constant;  K^d = equilibrium dissociation constant;  ke0 = distribution rate constant between first peripheral and biophase (effect) compartment; NMB = neuromuscular blockade;  V1 = volume of central compartment;  V2 = volume of first peripheral compartment;  V3 = volume of second peripheral compartment.