Pharmaceuticals as antifoulants: concept and principles.

The hypothesis that pharmaceuticals, with their known syntheses, chemical properties and primary mechanism of action would be an efficient source of new antifouling agents compatible with existing antifouling coating technology was tested. Twenty-three compounds at concentrations from 5 micrograms ml-1 to 40 ng ml-1 were tested for toxicity and inhibition of settlement of barnacle larvae. The compounds had a wide range of solubility in water and covered nine primary mechanisms of action in vertebrates. The upper level of potency was chosen because compounds that are highly potent have greater practical potential. The goal was to find compounds with high inhibition of settlement and low toxicity. Of the 23 compounds tested, 22 had significant effects on barnacle larvae. The variety of chemical structures and their variation in water solubility support the hypothesis that pharmaceuticals that are compatible with existing coatings technology should be considered as antifouling agents. Moreover, factors such as coating compatibility and environmental fate should be addressed early in the development process.