CHANGE: Male Birth Control Pill Is Coming, And It’s Going To Change Everything. “One injection would last for years. Research tells us that at least half of men would use it. . . . Vasalgel is essentially a polymer that’s injected under local anesthetic into the man’s sperm-carrying tubes, accessible through the scrotum — not in his penis or testicles as some authors have erred. It works by blocking sperm and is expected to be reversible through a second injection that dissolves the polymer.” Hmm. Expected to be reversible. I’d bank some sperm first, just in case.