A study by the Population
Council (Begay 2011) has found that every one of a panel of 41 commercially-available sexual
lubricants for sale in the USA
damaged human rectal and colonic cells in the test tube and compromised the
integrity of the single-cell layer that forms the surface of the rectum.
In contrast Carraguard, a gel formerly tried as an
experimental microbicide, did not damage cells
investigators found that four of the lubricants not only damaged the rectal
lining cells but appeared actively to increase HIV replication in the cell
They found that this
activity was caused by polyquaternium-15, a commonly-used cosmetic ingredient,
which has the property of facilitating HIV’s attachment to cells.
The study, whose original
findings were presented at the Microbicides 2010 Conference last year (Begay
complements the results of two other studies presented at that conference. The
first (Russo) tested
six popular lubricants and found that four stripped cells off the rectal
epithelium (surface membrane). The second (Gorbach)
found that men and women who took part in a rectal microbicide study and who
used lubricants for anal sex were three times more likely to be diagnosed with
gonorrhoea, chlamydia or syphilis than people who used no lube.
For the current survey
Othell Begay and colleagues from the Population Council tested a panel of 41
commonly-used lubricants. They tested their cytotoxic (cell-killing) activity
in two different ways and, by culturing them with HIV-infected cells, tested whether
they inhibited or enhanced viral replication. They used the ratio of their
cytotoxic and antiviral properties to calculate a “therapeutic index” (TI)
which predicted whether they might have any useful HIV-inhibiting potential in
The researchers compared
results from the 41 commercially-available lubes with Carraguard, as detailed above, and also with medical saline
solution and Gynol II, a spermicide
cream already known to be cytotoxic, as it contains nonoxynol-9, a compound
which has been known for ten years to damage cells and make users more
vulnerable to HIV.
They found that cells
treated with all the lubricants were damaged. A cell assay called TEER
(transepithelial electrical resistance) gauges cell integrity by testing their
resistance to electric current – whole cells transmit electricity less easily.
The researchers found that the TEER value for cells exposed to the lubricants
had dropped by 60% within two hours, as it did for cells exposed to Gynol II, whereas it remained steady for
cells exposed to Carraguard and
The researchers found only
one lubricant with mild anti-HIV activity – the vaginal moisturiser Replens. However the therapeutic index
for Replens was under 100
compared with a TI of over 3500 for Carraguard
– and Carraguard failed when tested
as an HIV-preventing microbicide.
researchers found that one brand of lubricant – Astroglide – appeared actively to enhance HIV replication in cells.
Astroglide has previously been
found to inhibit HIV in the test tube to some extent, not enhance it. This paradox can be
explained by the fact that, like nonoxynol-9, some lubricant ingredients
destroy viruses by dissolving their containing membrane – but do the same thing
to cell membranes, and thus have a net harmful effect.
The four (out of six) Astroglide lubricants that appeared to
increase viral replication were the only ones containing a compound called
polyquaternium-15 which, when tested, was found to be the cause.
In the Russo paper
presented last year it was theorised that the cytotoxic properties of
lubricants might be due to their being hyperosmolar. This means they contain more sugars and salts than
the body’s natural fluids. When hyperosmolar fluids come into contact with
cells they cause cells to secrete water and dry up.
Most of the lubricants
tests in this study were hyperosmolar. However four where hypo-osmolar, meaning they contained less sugar and salt than body
fluids, and one was iso-osmolar,
meaning it contained the same balance as body fluids, and none of these were
any less toxic. Replens, the least
toxic lubricant, was also the most acid, and it is known that vaginal acidity
help to protect against HIV transmission.
What does this mean for
users of lubricants? These are still preliminary results and much more research
is needed before detailed recommendations can be made.
It is important to
emphasise that the lubricants tested were all water-based. Water-based ‘lubes’ were
initially recommended for use in safer sex because they do not weaken condoms whereas oil-based ones cause them to burst.
Since it is the condom that is protecting users from HIV rather than the lube,
condom users should still be encouraged to use water-based lubes because condoms are also more likely to break, and
trauma to the rectal lining occur, with no lube.
However for people who for one reason or another do not use
condoms, water-based lubes may not the safest ones to use. A good compromise are the
silicone-based lubricants, which do not appear to damage cells and are also safe