Hydrogels containing monocaprin have potent microbicidal activities against sexually transmitted viruses and bacteria in vitro

Objective: To investigate the in vitro microbicidal and cytocidal potency o f monocaprin dissolved in pharmaceutical hydrogel formulations and to evalu ate their potential use as vaginal microbicides against sexually transmitte d pathogens such as herpes simplex virus type 2 (HSV-2), human immunodefici ency virus type 1 (HIV-1), Chlamydia trachomatis, and Neisseria gonorrhoeae . Methods: Gel formulations were mixed with equal volumes of virus/bacteria s uspensions in culture medium and incubated for 1 and 5 minutes. The reducti on in virus/bacteria titre was used as a measure of microbicidal activity. Similarly, gels were mixed with human semen to study their effect on leucoc ytes. The toxicity of the gels was tested in rabbits by the standard vagina l irritation test. Results: Gels containing 20 mM of monocaprin caused a greater than 100 000- fold inactivation of HSV-2 and Neisseria in I minute and of Chlamydia in 5 minutes. Similarly the gels caused a greater than 10 000-fold inactivation of HIV-1 in semen in 1 minute. They caused more than a 10 000-fold reductio n in the number of viable leucocytes in semen in 1 minute. No toxic effect on the vaginal mucose of rabbits was observed after daily exposure for 10 d ays. Conclusions: Hydrogels containing monocaprin are potent inactivators of sex ually transmitted viruses and bacteria in vitro. This simple lipid seems to be a feasible choice as a mucosal microbicide for prevention of sexually t ransmit-red infections. It is a natural compound found in certain foodstuff s such as milk and is therefore unlikely to cause harmful side effects in t he concentrations used.