ABSTRACT
Surface phenomena have a great impact on the formulation of pharmaceutical products, as they are directly related to solubility and dispersion of the active substance in a suitable medium or vehicle. Surface tension describes the interface between liquids and vapor. In order to approach a stable state, the system tends to reduce the surface free energy that may be achieved either by a reduction of interfacial tension or by a reduction of the interfacial area. Surface-active agents commonly known as surfactants are a group of substances that, when present at a low concentration in a system, adsorb onto the surfaces or interfaces of the system and alter to a marked degree the surface or interface free energies. The anionic surfactants adsorb on various kinds of substrates and give them an anionic charge. Some cationic surfactants can be also used as a germicide because of their strong ability to absorb to negatively charged materials in the living bodies of bacteria.
