The
importance of being informed about potential side effects of any medication
cannot be understated. However, when new medications come out there is always a
possibility that reports of side effects unknown to the pharmaceutical
companies and researchers emerge in the post marketing environment. But
sometimes there are reports of potential side effects that only affect a few
people and these should not necessarily be construed as a having widespread
applicability. A few incidents of blindness following Viagra use have been
reported in the United States but what is the validity of the claim?
It
is commonly known that transient visual disturbances can occur as a result of
taking Viagra. However, these side effects are noted on the rarer end of the
scale and appear to occur in 4% of the study participants. It has been argued
that this is due to that fact that sildenafil, the active ingredient in Viagra,
partially blocks an enzyme called PDE6, which is known to mediate the process
of transduction. Reviews and meta-analyses of clinical studies suggest that
these side effects can be lessened with appropriate dosage adjustment and
animal studies indicate that sildenafil does not have any major effect upon a normal
retina. Moreover, long-term toxicology studies to date do not demonstrate any adverse
visual side effects upon normal retinae. There is little possibility that such
a large number of studies that have systematically investigated the drug would
have such low quality or be unreliable.
Having
said that, we understand that there have been 50 lawsuits against Pfizer (the
manufacturer of Viagra) where individuals have claimed to have lost their sight
as a result of using Viagra. However, on examination most of these men had type
2 diabetes, which is widely known to cause blindness. We need to also consider
these 50 cases within the context of over 23 million men having been prescribed
Viagra globally without similar side effects.
There are certain medical conditions related to
vision which definitely contraindicate patients for Viagra. For example, we
would never prescribe for any patient who had retinitis pigmentosa or macular degeneration.
However, we are confident that sildenafil does not cause blindness. The men in
the US who have experienced blindness probably have their type 2 diabetes to
blame and that in turn can be blamed on their bad lifestyle choices over the
years. It is important not to have a closed mind, but Viagra really is one of
the safest medications around.
More information can be read about Viagra and visual disturbances here.