Abstract
The discovery of new biologically-therapeutically active structures continues to depend on screening and isolated observations of unexpected drug metabolites and drug activities. The selection of therapeutically improved and useful chemicals requires molecular modification. Refinements in intuitive and physicochemical methodology can provide shortcuts in random choices and permit extrapolations of some facets of activity with a variable degree of accuracy. The final decisions concerning the usefulness of a drug remain in the domain of experimental and clinical pharmacology.