This document discusses the combined effects of drugs, including synergism and antagonism. It provides examples of different types of synergism such as additive, supradditive, and potentiation. It also describes various types of antagonism including physical, chemical, physiological, dispositional, receptor, competitive, non-competitive, and irreversible antagonism. Competitive antagonism can be overcome by increasing the agonist concentration while non-competitive antagonism suppresses the maximum response through binding to an allosteric site.