Cocktails and contraception are two words seldom used together, particularly as the first usually leads to the opposite of the other. But in this case, they seem to gel quite well: a team of scientists were inspired by layered cocktails to create a new form of reversible male birth control. The pilot study was trialed in rats, with further tests soon underway. 

Around 40 percent of pregnancies worldwide, or 85 million pregnancies, were unintended in 2012. In the United States, that number was nearer to 45 percent of pregnancies. Nearly half of those worldwide ended in abortion and 13 percent in miscarriage.

“For decades, women have shouldered the main burden of contraception, but long-term use of contraceptives could give rise to several side effects,” wrote the authors from Nanchang University. “In the field of male contraception, apart from condoms and vasectomy, there is almost no appropriate alternative choice supplied for men.”

The researchers of the study, published in the journal ACS Nano, hope to change that in the future. Inspired by a cocktail called Galaxy, the team designed a male contraceptive method that prevented rats from impregnating females for more than 60 days. 

Even better, "the contraceptive time can be easily adjusted by varying the injection dose, while the quality of sexual life would not be impacted during the entire contraceptive period," said study author Dr Xiaolei Wang to IFLScience.

Now for the part everyone wants to know: What do men have to endure to achieve this birth control wonder? Well, first an injection of four ingredients into the vas deferens is needed. This can be done with the sequential injection of four liquid materials, some of which solidify later. The four key, baby-blocking ingredients are a hydrogel, gold nanoparticles, a chemical that breaks down the hydrogel and kills sperm (EDTA), and another layer of gold nanoparticles. Forget blue balls. Bring on gold balls!

After the injection, the hydrogel cross-linked into a solid. At the same time, the gold nanoparticles solidified at 37°C (98°F), which blocked both ends of the EDTA separately.

"The tricky part of this research is how to realize the 'transformation' of the injected reagent: At beginning, it should be a liquid, so we can inject it into the spermaduct easily," said Wang. "Afterward, the injected liquid should be spontaneously turned into a kind of gel, so as to stay inside the spermaduct and block the sperm."

To reverse the injection, the researchers shone a near-infrared lamp on the rats for a few minutes, which mixed and dissolved the layers of material and allowed the animals to produce offspring. This was the inspired portion of the research: the layers of a Galaxy cocktail don't mix because of an intermediate bubble drink between the top and bottom regions. This results in a temporary layered structure, but when external force is applied, the drink mixes into a uniform liquid. 

“Although condoms can prevent sexually transmitted diseases, they also affect the quality of sexual life and have a high failure rate (?19 percent). On the other hand, vasectomy is very effective (99 percent) but suffers from limited reversibility (<50 percent),” wrote the researchers. “For adult males with a fixed sexual life, [this new form] is more convenient, reasonable, and humanized to provide a medium- to long-term contraceptive method with flexible reversibility.”

If applicable to humans, men would be able to reverse the contraception and restore fertility at home using a near-infrared lamp for around five minutes to irradiate the area. "Most importantly, the embolism area could be readily opened at any time through a short-time noninvasive near-infrared irradiation," said Wang. "After the irradiation, fertility can be restored at once with minimized reclog risk."

For now, however, this is a promising pilot experiment and more research is needed to test the safety of the materials and confirm the findings in other species such as rabbits, dogs, pigs, and eventually humans.