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Relative Safety of OTC Sexual Lubricants for
Rectal Intercourse Kristin M. Sudol, Andrea R.
Wallace, Brian E. Ford, and David M. Phillips
Population Council, 1230 York Avenue, New York,
NY 10021
ABSTRACT
It has been documented that the majority
of men who have sex with men (MSM) use lubricants
during rectal intercourse. Many over-the-counter
(OTC) lubricants contain nonoxynol 9 (N-9). A
number of studies conducted in animals and humans
have presented evidence that lubricants
containing N-9 damage the delicate rectal
epithelium, thereby increasing the risk of
infection by HIV and other sexually transmitted
pathogens. This evidence prompted the Center for
Disease Control and Prevention (CDC), World
Health Organization (WHO), and CONRAD
(Contraceptive Research and Development) to
recommend that N-9 products should not be used
rectally. In light of this, we investigated which
products might be safe for rectal use.
Previously, we reported on a preliminary
screening of four lubricants, which are ranked in
terms of rectal safety. In the present study,
thirteen additional OTC lubricants have been
evaluated. Products assayed are Anal Lube,
Elbow Grease Light Gel, Eros Bodyglide, Forplay
Gel-PLUS, Liquid Silk, KY Jelly, Maximus, OMy
Natural, Probe Thick Rich, Slippery Stuff, Toys
in Babeland, Wet Classic, Wet Platinum, and PBS
as a control. Lubricants were assayed in vitro
for cytotoxicity using the XTT assay, and in mice
for the degree of rectal sloughing of epithelial
cells, and on preventing or enhancing infection
by herpes simplex type 2 (HSV-2).
All of the lubricants were shown to be more
cytotoxic then the PBS cell control. Anal Lube,
Forplay Gel-PLUS and Liquid Silk were the most
cytotoxic. Forplay Gel-PLUS caused 100 times more
cell sloughing then the control, while Anal Lube
and Probe Thick Rich caused 45 and 40 times more
cell sloughing respectively. With the exception
of Anal Lube and possibly Wet Classic, all of the
lubricants showed an enhancement of HSV-2
infection following rectal challenge. Because the
rectal challenge HSV-2 mouse system has a range
of variability that is difficult to control for,
it is difficult to detect a significant
difference between products that enhance
infection or those that protect against
infection. However, the assay is able to show a
trend toward one direction or another.
Significant differences were observed among the
lubricants. Because manufacturers do not divulge
the components within a product, it is difficult
to identify what attributes for the differences
observed. However, the observations enable us to
surmise which lubricants may be the safest for
use during rectal sex. Unfortunately, the US Food
and Drug Agency and other regulatory agencies do
not have as stringent regulation for lubricants
as compared to pharmaceuticals, because some of
these products may increase the risk of infection
during rectal intercourse.
Fig 2 Number of epithelial cells sloughed in
treatment groups as compared to PBS controls.
There is considerable variability among the
lubricants assayed. Toys in Babeland and Maximus
do not cause significant cell sloughing. While
Forplay Plus causes about 100 times more
epithelial cells to slough, Anal Lube and Probe
cause 40-45 times more cells to slough. Previous
studies evaluating N-9 showed a correlation
between an increase in cell sloughing and rectal
infection by HSV-2 (Phillips and Zacharopoulos,
Contraception 1998 57341-348, Phillips et al,
Contraception 2004 70 107-110).
METHODS
XTT Cytotoxicity XTT cytotoxicity assays were
performed in Caco-2 (human colo-rectal) cells as
previously described (Comley and Turner, Int J
Parasitol. 1990 2251-255). Rectal Cell
Sloughing Previously described (Sudol and
Phillips, Sexually Transmitted Diseases 2004
31346-359). The number of cells in each
treatment group was compared to the PBS control,
and were plotted as how many more cells are
sloughed for each formulation tested. (PBS being
1) Rectal HSV-2 Challenge Previously
described (Phillips and Zacharopoulos,
Contraception 1998 57341-348).
Figure 3 Effect of lubricants on HSV-2 infection
in mice following rectal challenge as compared to
control (Control id 100). Twenty mice were used
for each experiment and the experiments were
repeated twice. In all, 560 mice were used
(including controls). With the exception of Anal
Lube, KY Jelly, and possibly Liquid Silk and Wet
Classic all of the products tended to enhance
infection.
RESULTS
Fig 1 Cytotoxicity of sexual lubricants
compared to control as determined by the XTT
assay using colo-rectal cells. Cytotoxicity
ranged from those products exhibiting low
cytotoxicity including Slippery Stuff, Maximus
and Toys in Babeland, to products that displayed
relatively high toxicity, Anal Lube, Foreplay
Plus and Liquid Silk. Insoluble in water and
cannot be assayed by XTT.
CONCLUSIONS
Lubricants tested display a range of cytotoxicity
in the XTT assay. Ranging from the relatively low
cytotoxicity of Slippery Stuff, Maximus and Toys
in Babeland, to the far higher cytotoxicity of
Anal Lube, Foreplay Plus and Liquid
Silk. Products tested demonstrated very large
differences in causing sloughing of rectal
epithelial cells. Toys in Babeland and Maximus
showed little increase in number of cells
sloughed, while Anal Lube, Forplay Plus and Probe
caused an increase of 40 to 100 times more
sloughing than control. In the rectal challenge
mouse system most lubricants tended to enhance
the HSV-2 infection rate and none showed
significant protection.