It’s doubtful that anyone could dispute the claim that Viagra is the single most popular impotence treatment in the world. And we’re not only talking about its extremely high efficiency in the treatment of a condition that was a complete mystery for modern medicine as recently as 30 years ago, there’s also Viagra’s constant presence in the imagery on the mass media, the fact that this brand name is recognized throughout the world in a manner and to an extent that can’t be compared to any other medicine.
But, popularity and effectiveness aside, here we’ll be diving deep into the mechanism of action behind Viagra’s success. So, let’s answer the question – how does Viagra, the world’s most popular impotence pill actually work?
What’s on this page?
Chemical structure of Sildenafil – active ingredient in Viagra
The secret of Viagra’s effectiveness is its active ingredient, sildenafil. Discovered in early 1990s and patented in 1996 under the current name 1, sildenafil stood the test of time. This organic compound with a chemical formula C22H30N6O4S belongs to a class of pharmaceutical compounds called phosphodiesterase enzyme type 5 inhibitors, or PDE-5 inhibitors for short, hinting at its revolutionary mechanism of action.2
What are PDE-5 inhibitors?
Phosphodiesterase enzyme type 5 inhibitors are a class of pharmaceutical compounds that act by inhibiting the PDE-5 enzymes, organic compounds that exist naturally in the human body. These enzymes have a function of driving the blood away from the penis after ejaculation by narrowing the blood vessels within the organ. In healthy males, this type of enzyme plays a very important part in preventing priapism and injury to the penis. However, in men diagnosed with impotence, the levels of PDE-5 are unusually high.
It is important to note that PDE-5 enzymes act by degrading the cyclic guanosine monophosphate, or cGMP for short within the corpus cavernosum. Mechanism of action that is typical of Viagra includes protection of cGMP and prevention of its degradation by PDE-5.
What makes an erection happen (and go away)?
The science of erection can sound rather complicated and we cannot help but notice how much science there is even behind something that seems to be a rather simple biological function! So, let’s take a look at the biochemical processes behind erection.
Nitric oxide (NO), once present within the penis binds to the guanylate cyclase receptors, thus increasing the concentration of cGMP. When cGMP reaches certain levels, smooth muscle tissue lining the blood vessels within the penis will start to relax, causing increased blood flow within the spongy tissue of the penis and subsequently, an erection.
After ejaculation, PDE-5 enzymes will become more dominant, degrading cGMP molecules and essentially reversing the whole process, narrowing the blood vessels, taking the blood away from the penis and returning it to the flaccid state.3
Viagra mechanism of action
Sildenafil acts through a complex series of chemical reactions in order to relax smooth muscle tissue and allow for unimpeded blood flow within the penis. This process is enabled by the structural similarities between sildenafil and cGMP, which enables Viagra to act as a competitive binding agent of PDE-5. The result is an increased presence of cGMP and, by extension, stronger and longer lasting erection.
In layman’s terms, Viagra protects cGMP molecules within smooth muscle cells, including those around the blood vessels supplying the corpus cavernosum of the penis. With cGMP present in sufficient quantity, the smooth muscle tissue will relax (or stay relaxed), keeping the blood vessels opened wide. With blood vessels widened, naturally, the blood flow will also be increased. And sufficient blood flow is the most important condition for gaining and maintaining an erection.
This means that while Viagra isn’t “a magic medicine” and you still need sexual arousal to gain an erection, it will contribute to the removal of all physiological and biochemical obstacles to this process.
Are the effects of Viagra localized to the penis?
One of the most notable drawbacks of Viagra is that it isn’t 100% localized. This is why, in rare cases, it can also be used for the treatment of pulmonary arterial hypertension. 4
Like all other PDE-5 inhibitors, Viagra affects cGMP molecules within smooth muscle cells throughout the body, leading to an overall widening of the blood vessels. For healthy men, this effect is negligible and poses no threat whatsoever. But, for others, especially those who are more susceptible to its effects, or those who have been diagnosed with cardiovascular diseases, Viagra can cause problems by lowering the blood pressure and subsequently increasing the heart rate. This is why it’s very important to talk to your doctor about any potential contraindications that could influence the outcome of your treatment.
Conclusion
Ever since it became accessible to the general public back in 1998, Viagra stormed the markets and achieved amazing success among its customers. What’s more, it was the first PDE-5 inhibitor to be discovered and patented, revolutionizing ED treatment and making a giant leap from the previous medications that were uncomfortable to use, rather inefficient and bordering pseudoscience.
The mechanism of action introduced by Viagra proved to be the opposite – effective, reliable, easy to use. Its discovery changed everything for the men affected with impotence, allowing them to get their sex life back on track – something that was unthinkable in the 1970s or 80s.
With Viagra, PDE-5 inhibitors and their common mechanism of action became the norm for ED treatment worldwide that shaped the way we view this issue today.
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