Population Council Research that makes a difference

Personal lubricants have been available for decades, but knowledge about their impact on the transmission of STIs, including HIV, is limited. In the United States, for example, the US Food and Drug Administration (FDA) requires that manufacturers test lubricants for vaginal irritation, but does not require similar studies to ensure safety for rectal use.

Studying nonoxynol-9 for rectal use

Early Population Council research on lubricants showed that spermicides containing nonoxynol-9 (N-9) increased the probability of herpes simplex virus (HSV) infection in mice when the spermicide was delivered rectally prior to introducing the virus into the rectum.

For a subsequent study published in 2000 Council biomedical scientists tested KY Plus and ForPlay. The researchers concluded that the rectal use of these N-9–containing products caused a rapid exfoliation of extensive areas of the rectal epithelium in human volunteers. HIV target cells lie beneath the epithelium of the vagina/cervix and rectum. Thus, a break in the integrity of the epithelium could provide a passageway for HIV to make contact with the target cells.

"It is reasonable to assume that the loss of the protective epithelium would render a person more at risk for infection by HIV and other sexually transmitted pathogens. We, therefore, caution against the use of N-9–containing products during rectal intercourse," wrote the study team (abstract). In 2007, the FDA began requiring that labels for all contraceptive/spermicidal products containing N-9 bear the warning: "For vaginal use only; not for rectal (anal) use" (additional information: offsite link).

Investigating the role of lubricants in enhancing infection

These findings raised concerns that other commercially available sexual lubricants may enhance the probability of infection by sexually transmitted pathogens if used during rectal sex. To learn more, Population Council scientists evaluated the impact of five lubricants on cell cultures derived from the human colon. Researchers also evaluated the degree to which a product enhances or decreases infection with rectal administration of lubricant and HSV in animal models. Of the products tested, KY Plus and DeLUBE, were considerably more toxic than the saline controls, causing more cell sloughing and enhanced HSV infection (abstract).

In vitro study shows lubricants amplify HIV replication and cause rectal tissue damage

In vitro studies (i.e., experiments conducted in an artificial environment, such as in a test tube, not in a living organism) published in a 2011 journal article showed that some personal lubricants used during sexual intercourse significantly enhance the replication of the human immunodeficiency virus (HIV) and cause rectal tissue damage.

Of the hundreds of lubricants that are available to consumers, 41 water-based lubricants were tested. Low doses of four Astroglide formulations—Liquid, Warming Liquid, Glycerin & Paraben-Free Liquid, and Silken Secret—substantially amplified HIV replication in laboratory studies. All of these products contain either polyquaternium-15 or polyquaternium. Although not available for laboratory research, a compound that is chemically related to polyquaternium-15 called MADQUAT was studied. MADQUAT did in fact enhance the replication of HIV in those tests. Council researchers also showed that the majority of the tested lubricants damaged the integrity of rectal tissue in vitro, which may have implications for enhancing HIV transmission in humans as well (news release).

Additional research required

It is important to emphasize that these findings are from in vitro studies. What happens in the laboratory environment does not always happen in the human body. In fact, lubricants generally appear to play an important role in preventing the spread of HIV. Intercourse without them can damage cells by creating friction, which could cause tears in the epithelium, thus possibly promoting HIV transmission.

The field of rectal safety in humans is in its infancy, and it is uncertain whether the assays that are being used are sufficiently sensitive to detect minor differences among different products. With time, advances in methods for clinical evaluation may lead to a better understanding of which products are relatively safe and which cell and animal assays are likely to be most predictive of the safety situation in humans.