Some vaginal lubricants labelled as non-spermicidal may actually be toxic to sperm, a Swiss study suggests.
Out of four gels studied, only one, Pre-Seed, was non-toxic.
Lubricants are used not just to improve vaginal dryness during intercourse but also to ease the insertion of medical devices, including those used during the course of fertility treatment.
"It appears that most commercially available lubricants found in Switzerland are quite toxic to ejaculated sperm," researcher Dr. Alfred Senn of the Foundation for Andrology, Biology and Endocrinology of Reproduction, an independent foundation in Lausanne said.
In a study funded by Hygis, a Swiss company that resells pharmaceutical compounds but does not produce Pre-Seed, Dr Senn and his colleagues monitored the survival of donated sperm after 24 hours of exposure to commercially available lubricants labelled as non-spermicidal.
The gels were diluted to mimic typical exposure in the vagina.
One of the lubricants, Aquasonic Ultrasound Gel, is commonly used in ultrasonography to monitor follicle development in fertility patients before intercourse or insemination. The rest were products predominantly used by couples or as a vaginal lubricant for middle-aged and older women.
At the end of the 24 hours, three of the four gels, Felis Lubricant, Replens Vaginal Moisturiser and Aquasonic, had reduced sperm movement by up to 88%. Only Pre-Seed appeared benign.
"We were unaware of the mislabelling," said Dr Senn. "Lubricant producers may not have performed extended tests as we have done. The mislabelling may not be intentional."
Contacted about the findings, Kristin Stewart of Lil' Drug Store Products Company, the makers of Replens, suggested the use of Replens in the study did not comply with the company's instructions.
"Replens is recommended to be used at least two hours prior to intercourse. However, in this study the sperm was introduced directly to fresh Replens," Stewart said. "Therefore we believe the findings of this study as it pertains to Replens to be flawed."
The products tested did not contain chemical spermicides, but rather only included ingredients generally thought of as harmless, such as glycerin.
However, the researchers found that the slight acidity of these compounds created poor conditions for sperm. They also note the possibility of other direct impacts from the gels that might slow sperm down.
Pre-Seed was the only product tested that did not contain glycerin, according to the researchers' online paper in Fertility and Sterility.
They suggest that this gel may be most appropriate among those studied for patients trying to conceive, as well as for clinicians performing fertility procedures.
"Although it might be difficult to extrapolate these results to what is really happening during intercourse, our results suggest that the chances of conceiving are most likely to be affected," lead researcher Dr. Josefina Vargas said.
Dr. Mary Rosser, of the Albert Einstein College of Medicine in New York City, said she was not surprised by the findings and recommends Pre-Seed to her own patients.
"A lot of these lubricants probably do have toxic effects," she said. "So we tell people that are trying to get pregnant to try not to use anything. But, if you must, Pre-Seed has been well studied, appears to have no toxic effects, and would be fine to use."
Pre-Seed is not cheap, running about $20 (about R136) for a 40-gram tube. For a patient who may not be able to afford the lubricant, Dr. Rosser said some of her colleagues have recommended canola oil as a natural and cheap alternative.
K-Y Jelly and Astroglide may be more commonly used in the US than the other lubricants studied. However, Dr. Rosser said they are similar and probably just as toxic to sperm.
"Couples should be aware of the potential toxicity of commercially available lubricants," Dr. Senn advised. "These lubricants are designed to ease vaginal dryness, but they may not be designed for a couple trying to conceive."
(Reuters Health, Lynne Peeples, November 2010)