It's been a long time coming, but the first new male contraceptive for more than a century is likely to make most men wince.
The pioneering new treatment is a gel that’s injected into a man’s nether regions – blocking sperm and mimicking the effects of a vasectomy.
Vasalgel, a polymer gel is injected into the vas deferens – the tube which carries sperm to the penis.
Unlike a vasectomy, where the vas deferens is cut, Vasagel can be flushed out and reversed with another injection, of a baking soda solution.
Now, a new study, funded by the Parsemus Foundation, which owns the firm developing Vasalgel, has now found the new contraception can be reversed.
Scientists followed the progress of seven rabbits given the treatment for an average of 14 months, before the gel was flushed out.
They found sperm flow returned in all animals after the procedure was reversed.
Dr Donald Waller, lead author of the new study, said: “The results of the Vasalgel reversibility study in rabbits indicate the implant could be removed resulting in the quick return of sperm flow.
“We were pleased that the number of sperm and their motility after reversal were no different from baseline measures.
“More flushing during reversal may be needed to remove traces of the gel from the vas deferens, which appeared to impact other sperm characteristics.”
When it comes to male contraception, there are few options.
Typically, couples rely on female methods, including the Pill, and long-acting IUDs and implants.
But for many women, the side effects of hormone-based contraceptives prove frustrating and unpleasant.
Men have fewer options.
No new male contraceptives have emerged in more than a century, and men must rely on condoms, which are important in reducing the risk of sexually transmitted infections.
However, typically, not using condoms properly can increase the risk of pregnancy.
Other male methods include withdrawal, which has an even higher pregnancy rate.
And, finally vasectomy, which should be considered permanent, due to the fact reversal ops don’t always work.
It is into that void that Vasalgel fits.
Once injected into the scrotum, the gel remains in a soft state and allows water soluble molecules to pass.
But it stops larger structures, such as sperm.
It lasts for years, and important, is designed to be reversible.
To reverse its effects, a second injection is used to dissolve the Vasalgel.
A study published in 2016, found Vasalgel was an effective contraception in rabbits.
It stopped sperm being detected in semen samples as early as 29 days after the procedure.
And the effect lasted for at least 12 months.
Experts found the gel was safe and caused few side effects, having little effect on the structure of the vas deferens.
Today, a follow-up study published in the journal Basic and Clinical Andrology, reveals the reversal procedure works.
Seven rabbits, who produced no sperm in semen samples for 14 months thanks to Vasalgel, underwent a reversal.
A baking soda solution was injected into the vas deferens to dissolve the implants and clear the blockage.
The solution was found to successfully break down the gel.
And, scientists found sperm flow returned quickly.
Tests showed sperm concentrations and motility were similar to before the Vasalgel procedure, a positive sign of fertility.