One of the more promising methods of male contraception is reversible inhibition of sperm under guidance, or RISUG for short. The procedure is carried out by injecting a copolymer of styrene maleic anhydride (SMA) and dimethyl sulfoxide (DMSO) into the vasa deferentia. This has a number of effects on male fertility. Namely, it occludes the vas deferens whereby preventing the passage of the majority of sperm, it lowers the pH in the vas environment, and disrupts the plasma membrane of the sperm. The RISUG procedure is currently in late-stage development and will likely be approved by the Food and Drug Administration soon.

The RISUG injection is given by a physician into the lumen of the vas with the flow of material directed toward the ampulla of the vas. While there is some discomfort associated with the procedure, few other side effects have been reported. One exception is localized swelling, but no associated pain.(16) As opposed to a vasectomy procedure, RISUG does not allow sperm cells into the internal environment of the body. This prevents the formation of granulomas, which are the result of the body’s defense mechanisms attacking the sperm as though they were foreign in nature. One of the drawbacks of the procedure is that it is not self-administrated. However, this inconvenience is far outweighed by the convenience of only needing one treatment that can be effective for many years. In fact, early test subjects who received the injections have remained sterile for nearly a decade.(17) If a man decides he would like to father children, he can have the procedure reversed with another injection of sodium bicarbonate dissolved in water to flush the RISUG material.(18) Another method that has been successfully used to reverse RISUG is a combination of electrostimulation, massage, and vibration.(19) Fertility is restored within two or three months following the reversal procedure.(20)

Figure 1. A quick overview of how the RISUG works in creating an effective male contraceptive. Picture courtesy http://www.newmalecontraception.org/risug.htm

Analyses of semen in test subjects following the RISUG treatment showed the majority of sperm were prevented from being ejaculated by mechanical blockage, while those that were present in the ejaculate had anomalies that rendered them inviable. The sperm’s plasma membranes were broken, which caused the loss of the enzymes hyaluronidase, acrosin, and corona radiata penetrating enzyme. This is accomplished by the charge differences induced by the lowering of the pH in the vas lumen, which causes the proteins in the plasma membrane to become denatured.  In addition to the disrupted plasma membranes, the sperm in the ejaculate had curled tails and midpiece damage, making them incapable of motility.(18)

The semen of test subjects was also analyzed for biochemical composition. Each secretory gland in the male reproductive system has characteristic features that indicate the origins of the fluids present in the ejaculate. The seminal vesicles secrete both fructose and prostaglandins, the prostatic secretions have very high concentrations of citrate, zinc, and polyamines, and the epididymis produces glucosidase and carnitine. The analysis of semen in case studies showed no significant change in fructose and prostaglandins, which is an important criteria for determining whether RISUG is deleterious to prostate function. There was a lower presence of glucosidase and carnitine, however, which strongly suggests occlusion of the vas. This is a primary goal of the RISUG treatment.(17)


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