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Is Viagra a Male Contraceptive?

You’re stressed at work, money worries are getting you down and the kids are going through their “terrible teens”. Sex is the last thing on your mind. “Just a couple of those little blue pills”, you tell your doctor, to give you that “extra helping hand”. He obliges, scribbling out an illegible prescription. “And sir, don’t worry about contraception”, he tells you, “Viagra will cover that too”. You pause, thinking all your Christmases have come at once. Viagra really is a wonder drug. And then you wake up.  It was all a dream of course; or was it?

Viagra. The little blue pill has answered the prayers of millions of middle-aged men (and their partners) across the world since it was introduced by Pfizer Pharmaceuticals nearly 20 years ago. We all know the drug, know what it does; heck, some of you male readers may even have tried it yourself (purely out of curiosity, I hear you say). What you may not know, however, is that scientists have discovered that Viagra has effects on sperm cells that could see the drug labelled a so-called “anti-fertility” agent. So, has the world’s first male oral contraceptive drug really been sitting in our medicine cabinets all along?

Within weeks of Viagra being licenced for use, doctors had written over 100,000 prescriptions for its treatment of erectile dysfunction. Viagra is a muscle relaxant and works almost exclusively in the male reproductive tract. In order for an erection to arise (pardon the pun!), a spongy body of muscle within the penis (the corpus cavernosum), must relax in harmony with the surrounding blood vessels.  Viagra enhances this relaxation process upon sexual stimulation and as a result, can facilitate and maintain that once-elusive erection.

However, what has not been considered is that the male reproductive tract is full of muscle.  Contrary to popular belief, the male ejaculation is complex and relies on careful, co-ordinated contractions of several different muscles.  Most notable is the vas deferens – effectively a 5 mm wide sperm straw.  Contractions of this tube of muscle are essential to the ejaculation process, propelling the sperm to the urethra for expulsion.  Given that Viagra is a muscle relaxant, one would think it would relax the vas deferens too, no?

Yes. Due to the easy availability of human vas deferens tissue – which is extracted from male patients undergoing elective vasectomy procedures – researchers have been able to conduct experiments showing that Viagra does in fact relax the human vas deferens 1. What this means for your little swimmers remains to be discovered; the study was carried out on isolated muscle tissue, meaning that all traces of sperm and its associated fluid were removed during preparation of the tissue. In theory, one would expect Viagra to interfere with sperm transport along the vas deferens, resulting in a severely reduced sperm count in the ejaculate. This potential antifertility action would be a remarkable paradox for a drug so widely accepted as an enhancer of sexual function.

You may be thinking a multi-million dollar pharmaceutical company like Pfizer would surely have discovered if Viagra posed any risk to male fertility…. You’d be right. Pfizer and various other research groups have conducted a plethora of studies over the years to investigate just what Viagra does to sperm. Sperm are delicate little creatures, affected quite profoundly by small changes in their environment, so any potential threat to their homeostasis must be considered.  Indeed, distinct from its potential contraceptive action on the reproductive tract, there is substantial scientific evidence that Viagra affects sperm cells directly. When a patient pops a pill of Viagra, it dissolves in the blood before making the remote journey towards the male reproductive tract.  Here, Viagra exerts its facilitating role on erectile tissue but, in addition, scientists believe the drug reaches the seminal fluid and is exposed to the millions of sperm cells primed for emission.  However, as is the case with most science, the effects of this exposure on sperm cells are widely disputed.

Research conducted by David Glenn and colleagues at Queen’s University in Belfast has shown that Viagra may have “anti-fertility” effects on sperm cells. They conducted a noteworthy study in mice in which male mice were fed Viagra before being locked in a cage with a female and left to mate 2. As if the poor females had not suffered enough, they were killed a day later and their eggs examined for any signs of fertilisation. It was observed that the number of fertilised embryos was much lower in female mice that had been inseminated by Viagra-fuelled males compared to those mating with their Viagra-free rivals. Given the results of this study, it is possible that Viagra impairs fertility acutely in mice. But what about us humans?  

Some studies have highlighted that Viagra may interfere with sperm maturation in human males 3. One of the key stages of sperm maturation is the acrosome reaction –  a process whereby a bulbous, vesicle-like structure inside the sperm head fuses with the outer sperm cell membrane to release minute granules of digestive enzymes. The acrosome reaction is vital to fertilisation, and the timing of its occurrence is especially important; premature fusion of the outer membrane and acrosome creates sperm that are unable to fertilise the oocyte (egg cell). Indeed, Viagra is associated with causing a premature acrosome reaction in human sperm which means that it may have detrimental effects on male fertility.

On the contrary, there is a general consensus among researchers that Viagra acts like Red Bull to mammalian sperm, increasing both motility and velocity. This is suggested to have pro-fertility actions by increasing the probability of oocyte fertilisation. Furthermore, in a study conducted by Pfizer, Viagra was shown to have no adverse effects on sperm parameters in healthy human males; sperm count, sperm motility and the number of abnormal sperm were all normal 4. Great, perhaps Viagra does not lead to the formation of mutant sperm with three heads after all.

But again, why does it matter? Most Viagra users are pushing sixty and so their days of changing nappies and doing the school-run are long forgotten. While this may be true, Viagra is also the mainstay drug used to treat erectile dysfunction that occurs secondary to spinal injury and diabetes – conditions which affect a large number of young males worldwide. Furthermore, Viagra is used in fertility clinics to treat impotence problems that often occur when patients are asked to produce spur-of-the-moment semen samples. This is of particular relevance as any sperm abnormalities identified are likely to be attributed to the male himself, rather than reversible Viagra-induced effects.

So the question is, should we be throwing away our contraception and queueing up at the doctors for our own supply of “vitamin V”? Probably not. But whether you’re a daredevil student using Viagra for a laugh down at the Student Union, or that stressed middle-aged man who just needs an extra helping hand, you may want to think twice about what this pill could be doing to your precious little swimmers.

 

This article was specialist edited by Gwenllian Tawy and copy edited by Dominic Waugh

References

  1. http://onlinelibrary.wiley.com/doi/10.1038/sj.bjp.0703657/abstract;jsessionid=F7732617F32753509B58FC93C19A5DCB.f01t01
  2. http://www.fertstert.org/article/S0015-0282(07)04196-9/abstract
  3. http://www.fertstert.org/article/S0015-0282(06)04387-1/abstract
  4. http://onlinelibrary.wiley.com/doi/10.1046/j.0306-5251.2001.00033.x/abstract
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Published on: December 8, 2016

Filled Under: Features, Life Sciences

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