Your male patients are ready to give the 'male Pill' a
shot and their female partners feel long overdue for a
contraception vacation. Fears about permanent infertility
have even been laid to rest by a large scale review in
the April 29 issue of The Lancet which found that
men stopped 'shooting blanks' after they went off the
birth control. But still you have nothing to offer them.
What's the holdup?
STATUS
QUO
The biggest barrier to getting a male Pill on the market
appears to be apathy. "The lack of progress in developing
affordable, safe, effective and reversible male contraceptives
is due not to the biological complexity involved in
suppressing spermatogenesis, but rather to social and
economic/commercial restraints," concluded a 2000 report
by the male contraceptive program at US-based National
Institute of Child Health and Human Development (NICHD).
With some experts saying as many as 50% of US pregnancies
are unwanted, new methods are clearly needed.
Most
of the research is being done in India and China, where
growing populations make the issue rather more pressing
than in Canada, where the birthrate is declining. But
their work won't necessarily lead to products becoming
available here. "We have different standards and criteria
for acceptability," explains Dr Ronald Weiss, clinical
assistant professor of medicine at the University of
Ottawa and one of just two physicians in Canada who
offers scalpel-free vasectomies. "A lot of their studies
don't meet them."
Still,
men all over the world seem ready to give it a go
surveys have shown that between 13% and 80% of men would
be interested in trying a new contraceptive, depending
on the country and method studied. And they're increasingly
doing their bit. "Ten years ago, the number of tubal
ligations to vasectomies was two to one. Since that
time, the ratio has reversed," notes Dr Weiss.
IN
THE PIPELINE
The ideal male contraceptive, according to Dr Weiss,
would be easy to administer, reversible, safe, effective
at preventing pregnancy, locally-acting and non-occlusive.
Here are the contenders.
Hormonal
methods
Most experts agree a hormonal method will be the first
to get the green light, but they also think it's the
riskiest way to go.
Here's
how it works. In normal testes, a three-hormone cocktail
gives rise to testosterone, and ultimately sperm, production.
"If you add progestin, you shut down the synthesis of
those upstream hormones, intratesticular testosterone
will fall and you'll stop making sperm," explains Diana
Blithe, PhD, director of the NICHD male contraceptive
program. The catch is that blocking testosterone production
has system-wide effects, including loss of muscle mass
and libido. So enough testosterone has to be delivered
back into the serum to maintain normal function, without
re-stimulating spermatogenesis.
This
poses two problems: first, "there's no good oral formulation
of testosterone that doesn't cause hepatic damage,"
notes Dr Blithe; second, the systemic effects of hormone
therapy are, as we know only too well from the ongoing
estrogen HRT debate, nearly impossible to predict.
Non-hormonal
methods
RISUG, an acronym for Reversible Inhibition of Sperm
Under Guidance, is an injectable compound that partially
blocks the vas deferens. In 2002, Dr Weiss accompanied
a WHO team to India, where a phase III clinical is being
conducted, to review the procedure. He's the only Canadian
physician to have performed it.
"RISUG
forms a kind of meshwork that not only blocks the passage
of sperm, but also carries a slight electrical charge
that kills the sperm as they go by," he explains. The
compound a mix of styrene maleic anhydride and
dimethylsulfoxide is injected directly into the
vas deferens. Its advantages are many: the effect is
almost immediate, it seems to have very few side effects
and appears to last for at least 10 years. Studies in
primates have shown that the method is easily reversible
with a second injection that dissolves the meshwork.
Intra Vas
Device (IVD) is a set
of solid silicone plugs that are implanted in the vas
deferens to block the flow of sperm. In May, Shepherd
Medical announced FDA approval for a 90-man study of
the device to be conducted in the US. If all goes well,
the company expects to have European, Canadian and US
approval by 2010. The device is fitted to each patient,
and the two plugs are inserted into each side and sutured
onto the vas deferens wall. Removal of the IVD should
be as quick and easy as the implantation, which takes
about 20 minutes under local anesthetic.
Heat,
it's well known, affects sperm production. Capitalizing
on this observation, French researcher Dr Roger Mieusset
has conducted several clinical trials with various types
of suspensory, a special type of underwear designed
to warm the testes by holding them closer to the body.
One design that held them in the inguinal canal led
to 100% effective contraception.
|