Vaginal discomfort is a common cause of visits to the gynecologist. Vagina is prone to infections by potentially pathogenic bacteria owing to its proximity to the anus. A vaginal protection system is thus needed to prevent proliferation of pathogens. This protection system involves maintenance of a 3.5 to 4.5 acidic pH that renders the conditions unfavorable for the proliferation of potentially pathogenic organisms, while providing a suitable environment to acidophilus bacilli. Acidophilus bacilli highly metabolize under this situation and produce large amounts of lactic acid by glucose anaerobic fermentation. Lactic acid keeps its acidic pH and prevents uncontrolled growth of other bacteria present in the vagina.1

The characteristic pH of women of reproductive age, 3.5 - 4.5, is achieved due to the presence of a sufficient amount of lactic acid in the vagina. This molecule is thus important for maintaining a medium that favors the growth of lactobacilli in the vagina.1

Lactic acid hinders the growth of fungi, protozoa, Haemophilus and other pathogenic bacteria, which need a pH > 6.0. Lactic acid is the key element for the maintenance of vaginal health. Lactic acid compound produces hydrogen peroxide and favors the action of bacteriocins, which is unfavorable for a wide range of pathogens.1

In women with candidal vulvovaginitis, bacterial vaginosis or nonspecific vaginitis, the treatment should be focused on two key aspects - decrease in the pathogen quantity; and recovery of the vaginal pH.1

Therefore, formulations that can assist in the recovery of the lactobacilli population can be given along with antifungals or antibiotics in vaginal infections. Providing lactic acid to the vagina does away with the need to depend on the actions of the exogenous probiotics administered. Therefore, the appropriate treatment of vaginitis involves the administration of an antifungal or an antibiotic, as appropriate, followed by acidifying the vagina with lactic acid.1

A study evaluated the effect of treatment of bacterial vaginosis with high dose vaginal metronidazole and a following vaginal application of lactic acid in some patients. Bacterial vaginosis was diagnosed in 45 patients. The patients were divided into 3 groups. The first group comprised of 18 women who were given vaginal suppositories of metronidazole; in the second group, 20 women metronidazole and a following therapy with lactic acid. The third group (7 women) was the control group that received placebo therapy. In the metronidazole group, there was normalization of vaginal flora in 71.43%, intermediate vaginal flora in 14.3% and no change with therapy in 14.3%. In the second group, 94.1% patients were cured and in only one (5.9%) case, there was intermediate vaginal flora. In the control group, in 85.7% of the cases there was a lack of effect. Therefore, treatment with metronidazole showed good results in 71% of cases while adding lactic acid improved the therapeutic effect and achieved cure in about 94% of the cases.2

Application of vaginal lactic acid thus seems helpful in recolonization of the vagina with lactobacilli.

References

1. Haya J, García A, López-Manzanara C, et al. Importance of Lactic Acid in Maintaining Vaginal Health: A Review of Vaginitis and Vaginosis Etiopathogenic Bases and a Proposal for a New Treatment. Open Journal of Obstetrics and Gynecology 2014;4:787-799.
2. Andreeva P, Slavchev B, Kovachev SM, et al. Treatment of bacterial vaginosis with high dosage metronidazole and lactic acid. Akusherstvo i ginekologiia 2002;41(5):36-9.