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The aim of this study was to test the hypothesis that polyvinylpyrrolidone (PVP) would increase the critical micelle concentration (CMC) of nonoxynol-9 (N-9), providing a reduction in its irritation potential, while maintaining essential spermicidal activity. Solid coprecipitates of N-9 with PVP were manufactured with the use of a modified lyophilization process. The irritation potential of N-9 was estimated by an in vitro assay, monitoring the extent of hemolysis of red blood cells. CMCs of N-9 were measured in the presence of various concentrations of PVP. A modified Sander-Cramer assay was implemented to measure the spermicidal activity of N-9 and the N-9/PVP coprecipitates. With the use of the lyophilization process and more suitable solvents, solid coprecipitates of N-9/PVP were manufactured with no residual organic solvents. The irritation potential of N-9 was reduced when in the presence of PVP-50% hemolysis values increased from 0.054mM to more than 0.2mM. N-9 CMC values increased in the presence of PVP from 0.085mM (0% PVP) to 0.110mM (3.5% PVP) and 0.166mM (10% PVP). However, spermicidal activities ranged from 0.213mM to 0.238mM, N-9 remaining steady regardless of the amount of PVP. By use of N-9/PVP coprecipitates, the self-association properties and irritation potentials of N-9 were altered. This result suggests a process to produce a spermicidal product that reduces the detrimental implications to the vaginal epithelium while maintaining the essential spermicidal activity.