A new male contraceptive pill is on the horizon that temporarily stops sperm from swimming. According to pharmacologists at Weill Cornell Medicine and colleagues, the new birth control method doesn't mess with hormones but rather blocks a cellular signaling protein, acting as a "sperm-swim switch." The effect lasts for several hours after ingestion. So far, it's been tested with great success in mice. From BBC News":
By 24 hours, it appeared to have fully worn off with the next batch of sperm swimming normally.
One of the scientists, Dr Melanie Balbach from Weill Cornell Medicine in New York, said it showed promise as a reversible, easy-to-use contraceptive.
"On-demand male contraception via acute inhibition of soluble adenylyl cyclase" (Nature)