Our previous studies indicated that alexidine permeates into the walls of heated ReNu plastic bottles, thereby diminishing its concentration within the solution, thus allowing Fusarium growth. Using liquid chromatography-mass spectroscopy (LCMS), alexidine levels were measured in heated/unheated ReNu bottles stored for various time periods. These data were plotted as decreasing alexidine concentrations vs. time; ratios of the areas under the curves were calculated and compared with data derived from Fourier transform infrared (FTIR) spectroscopy absorptions of methanol extract evaporate residues of formerly alexidine-exposed bottle walls. FTIR studies showed that there was approximately 3.1 times more alexidine in the wall of the heated than the room temperature-stored bottle. The LCMS study showed that there was approximately 3.2 times more alexidine in the walls of heated bottles. Alexidine levels correlated closely with timed and dilution microbiological studies. Decreasing alexidine levels with time and heat strongly suggest alexidine-polyethylene interaction as the pharmaceutical failure mechanism of the worldwide Fusarium keratitis epidemic of 2004-2006.