Is Vasalgel the answer to male birth control?

male birth control

Non-hormonal male birth control trial underway in 2016

Earlier this year we brought you a story about a possible new male contraceptive device that’s essentially a ‘sperm switch’. This small device is designed to give men the option to ‘turn-off’ and ‘turn-on’ sperm flow.

If you missed the article, you can catch-up here.

Now there is news of a new potential male birth control option. Unlike the sperm switch, there is no surgery involved with this contraceptive. Also, this is not a pill designed to alter hormone levels. Instead, it is an injectable gel.

If successful, this male birth control may provide lasting contraception for men, giving couples more choices when it comes to family planning.

The absence of sperm

Researchers have been looking at ways to prevent sperm from exiting the vas deferens. This is the specialised tube responsible for transporting sperm from the testicles and into the ejaculate.

In this latest study, scientists have tested a gel called Vasalgel which was injected into the vas deferens of twelve fertile rabbits1. This gel is comprised of styrene-alt-maleic acid (SMA acid) dissolved in dimethyl sulfoxide.

The researchers analysed semen samples from the rabbits and found that 11 rabbits were azoospermic. One rabbit has a small number of sperm, although also became azoospermic following further testing.

The study lasted for one year and the rabbits remained sterile during this period. At the end of the trial, researcher removed the gel and sperm flow restored, along with reproductive capacity.

How does Vasalgel work?

This gel forms a hydrogel when injected into the vas deferens. This means that it stays in a soft gel-like form. It can flex and bond to the vasa deferentia walls.

Water soluble molecules can still pass through the tubes, but larger structures such as sperm cannot. Researchers believe that this technique could possibly decrease pressure in the sperm storage and production areas.

While Vasalgel has not yet undergone clinical trials in humans, this is about to commence later in 2016.

Revamping an old concept

News about various attempts to create safe and reliable male birth control options comes and goes. However, Vasalgel isn’t a new concept. In fact, there is almost three decades worth of research behind this product.

Smart RISUG® (Reversible Inhibition of Sperm Under Guidance), formally known as RISUG and synthetic polymer styrene maleic anhydride (SMA), was first created in India back in the late 1970’s2. However, insufficient number of volunteers to test the process halted the research.

Since development, this technology has been patented and refined. Now the intellectual property rights belong to an American not-for-profit company called Parsemus Foundation. It is this organisation which has rebranded the technology to Vasalgel and altered the composition of polymer.

Over the decades there have been several animal studies using of styrene maleic anhydride (SMA anhydride),  to determine its suitability as a male birth control option3, 4, 5. Pre-clinical and human trials have shown promise6, 7. However, it is the refined Vasalgel which has researchers interested.

Rather than using SMA anhydride, Vasalgel uses SAM acid. The problem with SMA anhydrides is that it may hydrolyze in aqueous conditions, where as SAM acid won’t. This makes SAM acid a more reliable option.

Will Vasalgel work?

The Parsemus Foundation certainly has high hopes for this male birth control. However, it is too early to tell if this is going to be effective for humans. The rabbit clinical trial showed promise. Nevertheless, the study group only comprised of twelve animals.

Even if Vasalgel does work, there are still many questions to be answered about the duration of contraception, reversing the procedure, and safely concerns.

These are some of the issues that will need to be clearly addressed before this gel could become a viable male birth control option.


  1. “Waller et al. (2016). Azoospermia in rabbits following an intravas injection of Vasalgel. Basic and Clinical Andrology. Volume 26, Issue 6. DOI: 10.1186/s12610-016-0033-8.”
  2. “Misro M. et al. (1979). Injectable non-occlusive chemical contraception in the male-I. Contraception. Volume 20, Issue 5, (pp. 467–73).”
  3. Koul V, Srivastava A, and Guha S. (1998). Reversibility with sodium bicarbonate of styrene maleic anhydride, an intravasal injectable contraceptive, in male rats. Contraception. Volume 58, Issue 4, (pp. 227–31).”
  4. “Guha S. (1999). Non-invasive reversal of intraluminal vas deferens polymer injection-induced azoospermia-technology. Asian Journal of Andrology, Volume 1, Issue 3 (pp. 131–4).”
  5. “Lohiya N et al. (2005). Preclinical evaluation for noninvasive reversal following long-term vas occlusion with styrene maleic anhydride in langur monkeys. Contraception. Volume 71, (pp.214–26.”
  6. “Guha S et al. (1993). Phase I clinical trial of an injectable contraceptive for the male. Contraception.  Volume 48, Issue 4, (pp. 367–75).”
  7. “Guha S et al. (1997). Phase II clinical trial of a vas deferens injectable contraceptive for the male. Contraception.  Volume 56, Issue 4, (pp. 245–50).”
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