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How RISUG Works

Trials and Tribulations: The Clinical History of RISUG

Like every (legal) drug, RISUG must still prove itself in clinical trials. A few analysts and regulatory scientists have questioned the safety of styrene maleic anhydride, which is also found in floor polishes. But so far, the gel and the procedure have proven to be safe. In fact, here's the clinical record of RISUG in India:

  • In 1993, a phase I clinical study enrolled 38 men married to women who had already received tubal ligations. Men received doses of the gel ranging from 5 to 140 milligrams. Low doses (5 to 20 milligrams) had no effect on sperm. When the men received the predicted therapeutic dose of RISUG (70 milligrams), all produced semen with no viable sperm within days after the injection. No long-term adverse effects occurred, although two subjects reported scrotal pain and enlargement.
  • In 1997, RISUG entered phase II clinical trials. This time, Guha enrolled 12 men whose wives used no other contraceptive method. He tested a fixed dose of 60 milligrams to see if pregnancy could be prevented for one year. This time, he found that sperm were inactivated immediately after the injection. No pregnancies occurred, and no adverse events were reported by the test subjects.
  • In 2001, phase III trials proved more of the same, this time with 139 men. That prompted a large-scale extension, the goal of which was to enroll 1,000 men. Unfortunately, the Indian government halted the study in 2002, citing concern over non-painful scrotal swelling. Guha and other scientists then had to produce more safety data to prove that RISUG would not harm men undergoing the procedure. Finally, after six years, experts decided the swelling was not a significant concern. Enrollment continued, and by 2011 500 Indian men had dropped their drawers in the name of science.
  • Through the years, other studies have also investigated the reversibility aspect of RISUG. Some have expressed concern that a man using the gel for a long time might not return to his pretreatment fertility after receiving the reversal injection. However, research published in 2005 provided data indicating that the testes, vas deferens and sperm of test subjects gradually returned to normal within 150 days of reversal.

Meanwhile, in February 2010, the Parsemus Foundation, an organization dedicated to funding neglected medical research, licensed the rights to develop RISUG -- as Vasalgel -- in the United States. It has since located a manufacturer to produce the polymer according to U.S. Food and Drug Administration guidelines and, in March 2012, initiated safety and efficacy studies in rabbits.

It could be years before RISUG/Vasalgel receives approval and enters the U.S. market as a readily available contraceptive -- long after it likely receives approval in India. Until then, men should hold on to their supply of condoms or decide, if they want a solution that's 100 percent effective, whether a vasectomy is right for them. And, of course, they can always take comfort knowing that the trials and tribulations of selecting a contraceptive are nothing compared to carrying and delivering a baby.

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