ABSTRACT
INTRODUCTION For a newly discovered molecule to become an active drug it must traverse through a multitude of physiologic barriers, both aqueous and nonaqueous; these barriers exist to protect our body from the noxious agents that can be toxic to our body. The system by which Nature chose to protect us is based on the solubility of compounds. A compound highly soluble in water or highly insoluble in water would not be able to penetrate the deeper tissues and thus rendered ineffective. Neutral compounds without any polarizable centers often prove to be inert pharmacologically; for example, fluorinated hydrocarbons, such as perfluorodecalin, which is a hexane structure with full fluorination. Fluorine is so highly electronegative that it pulls the electrons from the parent structure, making it an inert compound. Interactions at the site of action are often electrically driven and as a result, it is more likely that we will discover a compound that has weak acid or base properties as an active entity. This necessitates studies that would yield information on how well the compound will distribute throughout the body tissues and the lipophilic/hydrophilic balance of the molecular structure becomes the focus of studies at an early stage in preformulation.
