A reversible male contraceptive could be coming

For decades, women have shouldered most of the burden of contraception.

But long-term use of the pill can increase the risk of side effects for women such as blood clots or breast cancer, so scientists have been trialling a new form of reversible male contraceptive.

Until now common forms of male contraception are either short-term, such as condoms, or long-term, a vasectomy.

But condoms are actually only 85% effective when real life use is taken into consideration, and vasectomies, though effective, are often not reversible.

While trials of a new male pill, which works by lowering levels of testosterone and two hormones required for sperm production, have been showing promise, previous attempts to create a male pill, have resulted in side effects such as liver damage or low sex drive.

So a team of Chinese researchers set about devising a ‘medium-term’ reversible form of male contraception.

And, bear with us here, they drew inspiration from layered cocktails, such as the Galaxy, that bartenders make by layering colourful liquids in a glass.

If the drink is stirred or heated, the layers combine into a uniform liquid.

The Chinese team wondered if they could use a similar approach to inject layers of materials to block the vas deferens, the duct that conveys sperm from the testicle to the urethra.

They predicted that applying heat would cause the layers to mix, breaking them down and “unplugging the pipeline.”

The researchers decided to put their theory to the test using male rats.

They sequentially injected four layers of materials into the vas deferens: a hydrogel that forms a physical barrier to sperm; gold nanoparticles, which heat up when irradiated with near-infrared light; EDTA acid, a chemical that breaks down the hydrogel and also kills sperm; and, finally, another layer of gold nanoparticles.

Commenting on the findings, published in the journal ACS Nano, study leader Dr Xiaolei Wang, of Nanchang University, said: “The injected materials kept the rats from impregnating females for more than two months.”

However, when the researchers shone a near-infrared lamp on the rats for a few minutes, the layers mixed and dissolved, allowing the animals to produce offspring.

Dr Wang said the pilot experiment was “promising” but more research is needed to verify the safety of the materials uses.

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