Other vas-based methods
After being produced in the testes and stored in the epididymis, sperm pass through a tube called the vas deferens on their way to the penis. The vas deferens is the same tube that is cut in a vasectomy.
Many men throughout the world — more than half of the men in their forties in New Zealand, for example — get a vasectomy when they are finished having children (Sneyd et al., 2001). However, vasectomy is generally permanent. Therefore, researchers have long sought a reversible alternative to vasectomy. Several new approaches to vas deferens-based contraception are described below.
In China, a research team in the Sichuan province is conducting a clinical trial to evaluate the effectiveness, safety, and reversibility of a modified vasectomy technique. A tiny laser probe is inserted percutaneously through the scrotal skin into the vas deferens (no incision is necessary) and used to create scar tissue inside the vas deferens (personal communication, Dr. Y.Q. Gu , Nov. 2, 2005).
In the United States, high-intensity focused ultrasound (HIFU) has been tested as a way to nonsurgically occlude the vas for permanent contraception (Acker et al., 2003; Roberts et al., 2002). A small ultrasound transducer is clamped around the vas deferens and the scrotal skin, and the ultrasound waves are all focused on the vas deferens so that they do not excessively heat the skin they are passing through. Small proof-of-concept studies in dogs have established the proper power level and length of time needed (about 40-60 seconds), using equipment supplied by a company that already sells HIFU equipment for treating heart defects (Roberts et al., 2002; Warnking, 2004).
HIFU transducer on dog scrotum
(from Roberts, 2002)
The developer of the technology founded a start-up company to test and commercialize the sterilization method (Acker, 2005). The company hoped for success in attracting final funding, as the HIFU technology has already proven itself in heart defect treatment, and the application of HIFU to vas occlusion has been shown to be feasible in animal studies at Johns Hopkins Medical Institute. In addition, the completely non-invasive nature of HIFU makes it an attractive alternative in severely resource-limited settings where vasectomy and even RISUG would not be an option. However, in spring 2010 the company was turned down for a Gates Foundation Grand Challenges Explorations grant, a last hope for attracting greater attention to the idea in a difficult economic climate, and the company has disbanded.
Past vas-based methods
Chemical injection and injectable plug (polyurethane or silicone) are no longer being studied. For background on these methods, see the Vas section of the 2006 “Frontiers in Nonhormonal Male Contraception: The Next Step“. Various valves implanted in the vas periodically make the news, but these are not expected to be any more successful than the valves of the 1970′s, as any valve big enough to prevent leakage is also likely to rupture the vas. The VasClip vasectomy alternative is not recommended by the majority of vasectomy doctors who tried it because of unacceptably high failure rates.
The Intra Vas Device previously known as the Shug made it to Phase 1 trials before the 2008 economic crisis derailed it. The company has disbanded, and the men from the trial are not being followed. For background on the IVD’s rise and fall, see MCIP’s press releases or the Male Contraception Coalition newsletters.
Researchers in China were working on a mesh-like vas deferens plug that intentionally allowed subfertile levels of sperm to pass through it to reduce the buildup of pressure in the epididymis. This device is called an IVD (intra-vas device) but is distinct from the former Shepherd Medical’s IVD (personal communication, Dr. Y.Q. Gu , Nov. 2 & 12, 2005). For the past fifteen years, a research team at the National Research Institute for Family Planning in Beijing was collaborating with researchers in China ’s Guangdong province to do animal and human studies on this method. The plug was made of flexible synthetics and was anchored to the vas wall with a suture. Two very small holes near its tip allow some sperm to pass through.
The Chinese IVD was tiny (1 mm in outer diameter, 0.6~0.8 mm in inner diameter, and 17 mm in length). The researchers said that it could be easily inserted into the vas through a mini-incision and did not stretch the vas excessively. A phase II, randomized, controlled clinical trial completed in China compared the method’s effectiveness with that of no-scalpel vasectomy. It was somewhat less effective (94% instead of 98%) but the volunteers were happier with it, because of fewer side effects. Still, those numbers were a setback and mean that though the plug has been licensed for commercialization, this version had no future. The researchers had also made a version with copper added to it (probably to try to increase the effectiveness) and had published initial studies and reversal studies in dogs and rabbits. However, the researchers did not get renewed funding and have abandoned this work.
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