Rabbits Take One for the Team, Prove Male Contraceptive Works

The new contraceptive not only blocks the production of sperm, but also appears to be easily reversible.

by Jonathan Stern
Originally Published: 
roger rabbit and jessica rabbit

Men who aren’t in love with the current contraception options (ie. strapping on a latex balloon in the short term, or taking a scalpel to scrotum for the long) may soon have a better way. Scientists report that the male contraceptive Vasalgel, which was previously found to effectively block sperm production, is also completely reversible. Essentially, this gel acts like a non-surgical vasectomy — it blocks larger spermatozoa, but allows other liquid molecules to pass.

Last year scientists injected the Vasalgel into the vas deferens (sperm tubes) of rabbits. After waiting 29 to 36 days, they collected semen samples and found no evidence of live sperm. Better news? Vasalgel was effective for more than a year. Now a follow-up study, published in Basic and Clinical Andrology, showed that the process can be reversed. Seven of the rabbits who were injected 14 months previous were injected again, this time with sodium bicarbonate. The baking soda solution dissolved the previously injected gel and allowed sperm to do their thing again.

“The results of the Vasalgel reversibility study in rabbits indicate the implant could be removed resulting in a quick return of sperm flow,” said Donald Waller, Ph.D, the lead author of the study. “We were pleased that the number of sperm and their motility after reversal were no different from baseline measures.”

In other words, researchers found that, in a fairly short time, the rabbits were back to firing live ammunition. While scientists have to test Vasalgel on larger animals before human clinical trials start, the idea that guys could have a family planning strategy that isn’t all or nothing is encouraging.

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