Quantification of the in vitro activity of some compounds with spermicidal activity

Abstract

The in vitro spermicidal activity of the commonly used surfactant spermicides and the antiseptic chlorhexidine, were quantified in a statistically reproducible manner, using donor semen and image capture analysis. The spermicidal activity was expressed as the ED50 under defined assay conditions. Using these parameters, the order of spermicidal activity was: Menfegol > nonoxynol-9 approximately benzalkonium chloride > sodium docusate > chlorhexidine. These differences were statistically significant.

PIP: Results with a new quantitative, reproducible, comparative method for assessing sperm immobilizing activity of spermicides are provided. The Hamilton Thorn Motility Analyzer is a computer-assisted system using image capture analysis and phase contrast optics. The compounds studied were nonoxynol-9 (nonylphenoxypolyethoxyethanol, Triton N101, Sigma, UK), benzalkonium chloride (Sigma, UK), dioctylsodium sulphosuccinate (sodium docusate, Cyanamid, UK), Menfegol (p-menthanylphenyl polyoxyethylene, Eisai Pharma-Chem Europe Ltd) and chlorhexidine gluconate (ICI, UK). Test materials were dissolved in Tyrode's solution containing glucose, except for chlorhexidine which was diluted in 290 mM sucrose. All tests were read at 1 minute. Results, expressed in ED50s were: nonoxynol, 0.134 mg/ml; sodium docusate, 0.308; Menfegol, 0.104; benzalkonium chloride, 0.135; and chlorhexidine, 1.032. When the percent motility was plotted against exposure time, the biguanide antiseptic chlorhexidine immobilized sperm much faster than did the detergent spermicides. This method is considered superior than previous standards, the Sander-Cramer test and the IPPF Approved test, because it allows comparison of relative spermicidal activity between different agents. Since local concentrations of intravaginal spermicides tend to be much higher than the ED50s found here, it is likely that other factors such as local distribution and dispersion of the spermicide are of more practical importance.