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Dr Clare Morrison

Article by Dr Clare Morrison

How does Viagra work?


It’s quite possibly the most famous drug ever invented and has changed the sex lives of countless people the world over. While we all know what it is supposed to do, less of us know exactly why Viagra is so effective. Understanding this can really help you decide if it is the right drug for you or your partner. So, how does Viagra work? In this article, we’ll look at how Viagra works from a biological perspective. If you’ve ever experienced erectile dysfunction, having some practical knowledge of the ‘mechanics’ of an erection can be really helpful in understanding what is going on with your penis.

How does an erection work?

To understand how Viagra works, it’s first useful to have a working knowledge of what’s happening when a man gets aroused. The penis essentially has two functions:

● Urination – releasing urine from the bladder
● Ejaculation – when sperm is released from the prostate

For ejaculation to happen, the man needs to become sexually aroused. Next, the penis gets erect and stimulation of the gland results in ejaculation.

However, if the man cannot get an erection, or the erection disappears during sex (or cannot remain hard enough for penetration), ejaculation can’t happen. This might happen due to either physical problems (such as side-effects from medicine, high blood pressure, hormone problems, injury) or psychological problems (anxiety, guilt, stress). Viagra is the brand name for a drug called sildenafil, which is one of a range of drugs which help ensure the erection stays hard. Let’s look at what happens during a ‘normal’ erection, before seeing how viagra helps.

Step-by-step of a ‘normal’ erection

A man’s penis is a little like a balloon. On an anatomical level, the trunk of the penis has two spaces called corpus cavernosum, which fill with blood and this makes the penis erect. Blood enters the penis via arteries at the base and can fill these spaces and make the penis hard. Now, at the base of the penis there are muscles which are normally contracted and these prevent much blood entering the penis itself. However, when a man gets aroused, these muscles relax which opens up the arteries and allows blood to flow in.

When the man is not aroused, the muscles at the base of the penis constrict again and the blood flows out via veins.

Here’s a step by step of what happens on a biological level:

1. When the man feels sexually stimulated, the nervous system sends out a message to his erectile tissue and this releases nitric oxide.

2. The nitric oxide, in turn, stimulates another enzyme which produces messenger cyclic guanosine monophosphate (cGMP). In layman’s terms, this basically serves to relax the muscle tissues around the base of the penis, letting blood flow in.

3. After stimulation he will eventually ejaculate.

4. The body then sends another message to remove the cGMP, the muscles at the base of the penis relax again, and the penis becomes limp.

When erectile dysfunction occurs – something that almost all men will experience at some point – something will have gone wrong here. Either for physical or psychological reasons, somewhere along the line the cGMP stops being released, the muscles at the base of the penis constrict and the erection goes. This can be distressing and disappointing. The good news, however, is that Viagra can help most men in this situation.

What does Viagra do to help with erectile dysfunction?

Before answering this question, a little more biology. Another enzyme the body produces during the arousal process is PDE5. This enzyme plays a role in muscle contraction in the tissue around the base of the penis. If PDE5 is present, then the muscles at the base of the penis contract, less blood flows into the penis and the erection disappears.

So, how does Viagra work to counter this? Essentially, sildenafil, which is the active ingredient in Viagra, is one of a number of chemicals called PDE5-inhibitors. These drugs stop PDE5 from being released during an erection and therefore allow the penis to stay hard (there are various other PDE5 inhibitor drugs, which are the active ingredients in a range of other kinds of erectile dysfunction medication such as tadalafil). Viagra is one of the main PDE5 inhibitors and is the most well-known drug within this category.

So how does Viagra work exactly? Fundamentally, it’s the exact same process as described above. The difference, however, is that the sildenafil prevents PDE5 enzymes from being released, and this means that the muscles at the base of the penis stay ‘relaxed’ for longer allowing the user to stay hard.

Now, this doesn’t mean the man will stay hard the whole time the sildenafil is in the system! (If this does happen, it’s advised to contact a doctor). Rather, the sildenafil means that as the complex chemistry of the nervous system, enzymes and muscles tissue interact, the PDE5 will be suppressed when arousal occurs – and that means the penis will basically stay hard as long as the ‘excited’ feeling remains.

How long does it take for Viagra to work?

According to Pfizer, the company that makes Viagra, the drug will normally kick in within 30-60 minutes. That said, it can take as little as 12 minutes in some cases. Once taken the medication will remain in the system for about 24 hours, although over the course of the day it will gradually become less effective. Most men find that viagra works the first time they take it.

After about four hours, the sildenafil will be half removed, although it can still be expected to work effectively for up to ten hours. Thereafter, the effects may not be so strong – although this will vary between individuals for a variety of factors as well as the size of the dose.

How Viagra works if you have a physical issue?

Many men experience erectile dysfunction as a result of physical conditions, including high blood pressure, hormone changes, diabetes and the effects of other medication and drugs (including alcohol). Especially as men get older, it’s more likely they will experience some kind of physical erection troubles.

It’s always best to speak to a trained doctor before using Viagra, but in many cases it will make a big difference if a physical issue is present, because of the way it inhibits those PDE5 enzymes.

That said, erectile dysfunction is also linked to lifestyle factors too. So those who are overweight, and who smoke or drink a lot are most at risk – so it’s worth considering lifestyle changes to avoid erection problems.

How does Viagra work if your problem is mental?

Many men’s erection problems arise due to psychological factors, be that issues to do with guilt, shame, childhood trauma, or alternatively, a highly stressful and tiring lifestyle. It’s possible for some men to get into a negative thinking cycle whereby they experience erection problems once, and then become anxious it will happen again. Due to the anxiety they feel, they then cannot enjoy sex and fail to get aroused again – a real negative spiral.

In any of these cases, Viagra certainly can help. It can give the man confidence in the bedroom and, after a few positive experiences they may feel they no longer need to use the drug.

However, it is always worth considering talking about these issues – either with a GP, a trained sex therapist and, most importantly, partner. This can help get to the root of the issue.

How well does viagra work?

Viagra is one of the best-known medications on earth, is regularly referred to in pop culture and has been used by millions of men the world over to have harder, longer lasting erections.

While there are certainly some potential side effects with Viagra (speak to a medical expert about existing physical conditions and any medications used) the vast majority of users experience no serious problems with the drug.

So, now you know how Viagra works, talk about taking the drug with your partner and speak to a trained professional to order your next prescription.