Characterization of commercially available vaginal lubricants: a safety perspective

Abstract

Vaginal lubricants are widely used by women to help solve intercourse difficulties or as enhancers, but recent reports raise questions about their safety. Twelve commercially available gel products were tested for pH value, pH buffering capacity, osmolality and cytotoxicity relevant to vaginal delivery. Obtained data were analyzed in light of the recent Advisory Note by the World Health Organization (WHO) for personal lubricants to be concomitantly used with condoms. Results showed that most products do not comply with pH and osmolality recommended standards, thus posing a potential hazard. Four products presented values of osmolality around three-times higher than the maximum acceptable limit of 1200 mOsm/kg. In vitro cell testing further identified substantial cytotoxicity even at 1:100 dilutions for three products, contrasting with no significant effect of up to at least a 1:5 dilution of a Universal Placebo gel. However, no direct correlation between these last results and pH or osmolality was found, thus suggesting that the individual toxicity of specific formulation components plays an important role in the outcome of a particular product. Although further assessment is required, these results highlight potential safety issues related to the formulation of commercially available vaginal lubricants.

Figure 1

The relevant and absolute buffering capacity of tested products in normal saline. Individual columns and vertical bars represent mean and SD values, respectively (n = 3). (*) Denotes a significant difference (p ˂ 0.05) when comparing to the values of the relevant or absolute buffering capacity for plain normal saline.

Figure 2

Relevant and absolute buffering capacity of tested products in vaginal fluid simulant (VFS). Individual columns and vertical bars represent mean and SD values, respectively (n = 2–3). (*) Denotes a significant difference (p ˂ 0.05) when comparing to values of relevant or absolute buffering capacity for plain VFS.

Figure 3

Cytotoxicity of tested products to the HeLa cell line after 24 h incubation at 1:5, 1:20 and 1:100 dilution ratios in medium, as assessed by the LDH assay. Individual columns and vertical bars represent mean and SD values, respectively (n = 3). Horizontal dotted lines at 0% and 100% correspond to low and high controls, respectively (associated gray shades stand for SD values). (*) Denotes a significant difference (p ˂ 0.05) when comparing to cells incubated with the Universal Placebo at the same dilution ratio.

Figure 4

Correlation of cytotoxicity, expressed as half-maximal cytotoxic concentration (CC₅₀) values, with the (A) osmolality or (B) pH of the selected products. Individual points are mean values, and the straight line corresponds to linear regression (R² values presented in the graphs).