Solubilization and in vitro spermicidal assessment of nonoxynol-9 and selected fractions using rabbit spermatozoa

Selected oligomers representing the high, medium, and low molecular weight fractions of the spermicidal agent Nonoxynol-9 (N-9) were separated by HPLC. Nonoxynol-9 and the isolated fractions were formulated with polyvinylpyrrolidone (PVP) in order to increase their water solubility, particularly that of the insoluble low molecular weight fraction. The in vitro spermicidal activity of three molecular weight fractions were compared to that of N-9, using rabbit spermatozoa, at equimolar concentrations. Nonoxynol-9/PVP was far more effective in immobilizing the sperm than either N-9 alone or the separate fractions. The relative spermicidal activity of the oligomers was of the order middle molecular weight greater than high molecular weight greater than low molecular weight.