Designing safer (soft) drugs by avoiding the formation of toxic and oxidative metabolites.

Integration metabolic considerations into the drug-design process can allow safer pharmaceuticals to be designed. "Soft" drugs are designed to be deactivated in a predictable and controllable way after achieving their therapeutic role. They are designed to be metabolized rapidly and by avoiding oxidative pathways into inactive and nontoxic species. Successful application of such design principles has already resulted in a number of marketed drugs. The present article illustrates advantages inherent in avoiding the formation of oxidative metabolites, with examples that include soft bufuralol analogs and soft insecticides such as chlorobenzilate and malathion. Design principles for various soft drug classes are briefly summarized together with computerized tools intended to make the application of these principles more quantitative and more accessible.