Figure 10-19 Schematic representation of the interaction of a short-acting antagonist with a longer-acting agonist resulting in resedation. The upper curve shows disappearance of agonist from blood, and the lower curve shows disappearance of antagonist from plasma. Four conditions are represented: I, agonist response; II, antagonist response (the antagonist reverses the agonist effect); III, agonist response (resedation or resumption of agonist response with disappearance of short-lasting antagonist); and IV, no drug effect, with disappearance of both agonist and antagonist (both drugs are below the therapeutic level).