The possible interaction has been studied between plastics and several drugs and pharmaceutical adjuvants such as parabens, quaternary ammonium salts, and HCO-50 (polyoxyethylene derivative of hydrogenated castor oil). It was found that hydrophobic interaction plays a major role in adsorption of parabens to several plastics studied. Studies on the effect of temperature on adsorption and desorption suggest that the drug-binding sites of plastics may be hidden in the structure at low temperature and unfolded to the surface by configuration change at high temperature. HCO-50 was non-selectively adsorbed to all plastics studied and maximum adsorption occured near the region of the critical micelle concentration of HCO-50.
