Next Stop for Male Contraception: The Vas Deferens

Soumya Vemuganti

One of the most promising non-hormonal male contraceptives in the pipeline is a gel that would leave sperm unable to fertilize eggs.

today have two options when it comes to birth control: condoms or vasectomy. 
Condoms are a low-tech barrier method and can prevent both pregnancy
and transmission of STDs.  However, the effectiveness of a condom
is dramatically decreased if not used correctly, and studies have shown
a more realistic 15%
failure rate
Vasectomy promises permanent birth control, through
an invasive procedure which cuts the vas deferens, creating a block
in the tube which sperm pass through before ejaculation.  While
the surgery alone may turn off some men, the delay in effectiveness
is also unappealing, since it can take up to 3 months for a vasectomy to be successful.  Some
men experience swelling of the epididymis due to the blocking of fluid
passing through the vas deferens, a condition called epididymitis. 
While vasectomy
is an option,
often fertility does not return to pre-vasectomy levels.  Vasectomy
is not ideal for many men due to the need for surgical incision, a delay
in effectiveness, and reduced fertility following reversal.

we track the complete cycle of male fertility, other possibilities for
male contraception emerge.  Male fertility begins with the production
of sperm in the testes, followed by the sperm’s journey through the
male reproductive tract.  This voyage starts in the epididymis
(a set of tightly twisted tubes where sperm are stored and mature) and
continues in the vas deferens, a second tube that connects to the epididymis
and serves as the passageway for sperm when they are released from the
body.  Researchers are exploiting the fact that sperm make this
journey before reaching the egg (in the female reproductive tract) by
targeting sperm in the vas deferens or immediately after they released. 
These targeted male contraceptive approaches are non-hormonal, resulting
in fewer systemic side effects.    

of the most promising non-hormonal male contraceptives in the pipeline
is RISUG, or Reversible Inhibition of Sperm Under Guidance.  Researchers
in India have developed a polymer gel that once injected into the vas
deferens coats the wall of the tube.  This gel will come in contact
with sperm passing through the vas deferens and burst the cell membranes, leaving sperm unable to fertilize an egg. 
The polymer does not completely block the vas deferens and allows for
fluid to pass through, diminishing the chances of fluid buildup and
subsequent epididymitis.  It only takes minutes for the polymer
to bind and contraceptive effects are seen immediately, within days not months like a vasectomy.  Both application
and reversal of RISUG use no-scalpel methods, and therefore do not involve
cutting of the vas deferens.  Despite the non-invasive and immediate
effectiveness of RISUG, the beauty of this contraceptive lies in its
name:  RISUG is reversible.  A simple injection can flush out the
polymer and restore fertility within 150 days; however, this has only
been tested in primates.  The obvious next step would be to test
reversibility on human subjects, some of which have been using RISUG
for over 10 years.  RISUG is in phase
III clinical trials
India as of March 2007.  Clinical studies of RISUG must be repeated
on a larger scale using US and international guidelines before it can
be considered for human studies in other countries. 

very similar non-hormonal male contraceptive is the intra vas device,
or IVD.  This method requires much
less cutting
when compared
to a vasectomy, and works by a plug inserted into the vas deferens. 
Clinical trials in Minnesota are using a soft silicone based plug while Chinese scientists are using a plug made from urethane
and nylon.  This approach prevents sperm from passing through the
vas deferens, but allows for some fluid to pass through.  Again,
reversibility has only been tested in primates, but the results are very promising with fertility
returning to pre-IVD levels one month following removal.  The FDA
approved clinical trials of the IVD in 2006 and it is currently in clinical trials on 90 individuals across the US.   

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devices that effect sperm passing though the male reproductive tract
are effective contraceptives, they do not provide any STD protection. 
Spermicides that are also microbicides can offer both contraceptive
and STD protection. They are often used as lubrication alone or with
condoms and work by binding to the sperm membrane, thereby blocking
sperm movement.  Nonoxynol-9 , a popular detergent-based spermicide, was
shown to promote HIV and HPV transmission through vaginal and cervical
abrasions caused by detergents.  Taking into consideration the
adverse side effects, the FDA has mandated warning labels on nonoxynol-9
containing products, leaving a void of safe and effective spermicides
available for consumers.  However, there are a few promising non-detergent
based spermicides that offer both contraceptive and STD protection. 
These include spermicides which create a physical barrier (UsherCell and Pro2000) and ones which acidify the environment and
utilize natural defense mechanisms (BufferGel and Acidform).  Many of these spermicides are in clinical trials; however, there still remains a concern about
the effectiveness of spermicides as contraceptives.  Alone they
have a high failure rate of
with typical use, however
when used in combination with condoms, spermicides can increase the effectiveness of both products. 

it is easy to imagine a contraceptive that would block sperm from binding
to the egg.  The closest to this is a "sugar
", in simple terms,
an enzyme inhibitor being developed by a US
that mimics the
sugary coating of the egg.  This sugar mimic is added to sperm
in the epididymis and binds to the sperm head, thus preventing treated
sperm from binding to the egg.  This contraceptive is in early
developmental stages, as it was found to be 90%
in rats with
no side effects. 

across the world are working toward developing a safe and effective
male contraceptive.  They are using a diverse set of approaches,
including arresting sperm production, blocking sperm entry into the
female reproductive tract, and interfering with sperm-egg binding. 
Compared to systemic hormonal methods, targeted mechanisms promise fewer
side effects.  However, the future of male contraception depends
upon not only the bright minds that fuel the research, but the funds
to support the development and testing required for implementation. 
With an increase in public interest hopefully we will find a rise in
funding, with the ultimate goal of developing an effective, non-hormonal,
male contraceptive.

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