that attach to the vas deferens wall. It is surgically inserted into the vas deferens and must also be removed surgically. Shug human trials showed a 97% decrease in sperm motility through the vas deferens. However, plugs have been shown to have a lower efficacy rate when compared to traditional vasectomy overall. Intravasal thread (IVT) Insertion of an intravasal thread (IVT), also known as an intravasal device (IVD), in the vas deferens has been shown to inhibit sperm transport via mechanical obstruction and the removal of the IVT results in restored vas deferens patency. However, this method has differential species-specific results: in pigs, a plastic IVT had no significant effect on sperm count; in dogs, a plastic and polyethylene IVT consistently blocked sperm transport during the experimental period and removal of the device restored sperm transport after a period of two weeks; and in human subjects, a urethane-coated nylon IVT resulted in significantly reduced sperm count but could not guarantee absolute sterility at the same rate as a vasectomy. RISUG Reversible inhibition of sperm under guidance (RISUG) is a non-toxic polymer gel-based contraceptive that is injected into the lumen of the vas deferens and results in infertility within 10 days following injection. RISUG is composed of styrene maleic anhydride (SMA) dissolved in dimethyl sulfoxide (dimethyl sulfoxide), which is believed to both partially occlude the vas deferens by coating the inner walls of the vas deferens with the polymer chemical, while also deactivating the sperm that are able to pass through the partially occluded vas deferens, thereby preventing successful fertilization. The exact mechanism of the deactivation effect on sperm is still unknown. RISUG inhibits sperm transport but allows fluid to pass through, which prevents pressure from building up in the vas deferens. RISUG has been shown successful in previous human clinical trials in India and is currently undergoing Phase III clinical trials. Vasalgel Vasalgel was inspired by RISUG and created by the Parsemus Foundation in order to be used outside of India. Vasalgel is composed of 25% styrene-alt-maleic acid (SMA acid) dissolved in dimethyl sulfoxide. The major difference between RISUG and Vasalgel is that Vasalgel is composed of SMA acid without SMA anhydride, which allows for a longer shelf-life, smaller probability of hydrolysis to an acid, and less complex production process. Vasalgel was successful in achieving azoospermia in rabbits within 36 days of injection, as well as returned vas deferens patency,