Viagra (Sildenafil)

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Medically reviewed by
Dr Daniel Atkinson
GP Clinical Lead
on August 02, 2022.
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What is Viagra (sildenafil)?

It’s seen as the “first” ED treatment to appear on the market, and it’s been used by millions of men. The pharmaceutical company Pfizer launched the Viagra brand name as well as the distinctive, diamond-shaped pill design.

All of this has helped the Viagra pill become the biggest player in the ED field. But let’s put its status to one side for a moment. How does it work? The main ingredient in Viagra is called sildenafil citrate, and it helps with erections by relaxing the blood vessels of the penis.

An erection from relaxed blood vessels?

It may sound counterintuitive, but it’s not — when your blood vessels are too tight, blood can’t get to the penis quite as well. Sildenafil citrate improves your circulation, and this allows you to get firmer erections that last long enough for sex.

While it’s the brand-name treatment, there are other names for Viagra too. The product Sildenafil (with a capital S) is generic Viagra. Sildenafil works in exactly the same way as Viagra but is made by different companies. While it contains the same active ingredient, a Sildenafil pill can have a unique design and packaging depending on who makes it. And because it doesn’t come with that brand-name price tag, Sildenafil is usually cheaper.

Viagra and Sildenafil are taken as-needed, meaning you’ll take your tablet around an hour before sex. It’ll work for around five hours, and you shouldn’t take more than one in a 24-hour period. Don’t worry, though — that doesn’t mean you’re going to have an erection for five whole hours. ED treatments, like Viagra and Sildenafil, help you get an erection but you still have to be aroused for them to work.

Some quick Viagra history

Although Viagra has been approved to treat erectile dysfunction for over two decades, it was originally developed in 1989 by two Pfizer scientists — Peter Dunn and Albert Wood — to treat high blood pressure and angina.

Trials for Viagra as a treatment for heart disease got underway in the early 90s, but showed little promise. However, participants in the trials did notice an increase in the number of erections they were getting. This led to pilot studies of its use as an ED treatment. The American FDA approved Viagra as an ED medication in 1998.

Pfizer retained the Viagra patent for 15 years, until it expired in the UK in 2013. This allowed other companies to start making their own versions of Viagra with the same active ingredient (sildenafil citrate). Even Pfizer started producing a generic Viagra.

Sildenafil citrate (the main ingredient in Sildenafil and Viagra) is also sold as Revatio, a medication for pulmonary arterial hypertension, or PAH.

What does a Viagra pill look like?

Blue Viagra tablet

The Viagra pill or tablet is blue in color, and shaped like a diamond. Viagra pills have “Pfizer” written on one side and the dosage on the other (so either VGR25, VGR50 or VGR100 to indicate 25mg, 50mg or 100mg doses). 

If you’re taking Viagra Connect, which is a form of the drug that you can buy without a prescription, these pills will look the same as Viagra. Viagra Connect is only available as a 50mg though, so the tablets have ‘V50’ written on one side.

What are the benefits of Viagra?

In terms of the benefits of Viagra for men, you’re getting a tried-and-tested ED treatment with a household name. Most men find that Viagra works the first or second time they try it, and it offers some flexibility with the available doses: 25mg, 50mg and 100mg. Another benefit of its status as a well-known and popular drug for ED is its availability. Because it’s so widespread, you can get it from a range of places (even without a prescription if you get the 50mg Viagra Connect). So you won’t have to look for long to find the best place to buy Viagra for you.

You’re likely to start on the 50mg dosage but if you notice side effects this can be adjusted to 25mg, but if the 50mg dose doesn’t work as well as you’d like it to, the 100mg option is there for you.

Another string to Viagra’s bow is that it’s easy to use. You take one tablet one hour before sex and it should remain active in the body for up to five hours. So plenty of time to enjoy intimacy with your partner.

Can you only get Viagra for men?

Yes. Viagra pills are for men only. In the US, there’s a medication for women called Addyi, which is sometimes known as “female Viagra,” but it’s used to treat a completely different issue and works in an entirely different way. Addyi is prescribed to help increase female arousal rather than impact the physical mechanics of sex, so it shouldn’t be confused with male Viagra.

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What is Generic Viagra?

Sildenafil is the generic version of the ED treatment Viagra. It has the same active ingredient (sildenafil citrate) but it might have a couple of differences. These differences can include its specific look, branding, formulation and price.

Sildenafil can be manufactured by other companies and can have a different appearance, price and inactive ingredient list depending on the manufacturer. However, all Sildenafil products must prove their bioequivalence before they are approved, which means it has the same amount of active ingredient and produces the same result.

Think of it like ibuprofen, the medication you might take for headaches. You can go to a supermarket and pick up Nurofen, which is a brand-name version of ibuprofen and probably a bit more expensive. The shop might also have several other types of ibuprofen, including their own line (likely the cheapest). These medications will all help you with your headache, but the size and color of the pill, the branding on the box and the inactive ingredients can all be a little bit different.

Sildenafil was released in 2013, after the Viagra patent expired and it tends to cost a lot less. So if you’re looking for a cheaper product, you may want to choose Sildenafil.

Sildenafil vs sildenafil citrate: what’s the difference?

The difference between Sildenafil and sildenafil citrate comes down to semantics, really. Sildenafil citrate is the name of the active ingredient in Viagra (and Sildenafil) whereas Sildenafil (with a capital ‘S’) is the generic version of Viagra — a medication containing sildenafil citrate. However, sometimes “sildenafil” is used as shorthand for sildenafil citrate. Depending on the sentence you see it in, you can usually grasp whether it’s referring to the medication or the ingredient.

Although dosage can differ, all sildenafil citrate tablets should work just about the same, no matter what company makes them. The main differences between them will be the packaging, price and inactive ingredients.

What about Viagra Connect?

Viagra Connect is a 50mg dose of sildenafil that’s only available in the UK.

Pfizer launched Viagra Connect in the UK in 2018, it’s a rebranded version of Viagra 50. It works in the same way as Viagra, and it’s got the same active ingredient in it.

The one big difference is that you don’t need a prescription to buy it, although it’s still not an “over the counter” medication as such. Yes, it can be purchased at pharmacies but you’ll still need to speak with a pharmacist to make sure it’s safe for you to take.

How to take Viagra

Taking Viagra is simple. Just take your pill with a glass of water. It doesn’t matter if you take Viagra with food or not, and it doesn’t interact with alcohol. However, a heavy or fatty meal can slow it down and alcohol can make ED worse, so you should consume it in moderation.

Your medication will come with a patient information leaflet containing detailed instructions. Always read the leaflet before taking Viagra for the first time.

How long does it take for Viagra to work?

Viagra starts to work within 30-60 minutes of taking it and is active in the body for up to five hours. Although your age, diet and health can all impact how long Viagra takes to work.

A five-hour window means you shouldn’t have to worry too much about timing your Viagra dose.

How much Viagra should I take?

You shouldn’t take more than one Viagra tablet over a 24 hour period. If you use Viagra and find that it doesn’t work as effectively as it should, or if you get any side effects, let your doctor know. They may decide to change your dose.

Viagra comes in multiple dosages, from 25mg up to 100mg. This is a broader range than some other ED drugs, so it may be easier to find the dose that’s right for you. The “typical” dose is 50mg, which is what you’ll normally start with when taking the drug for the first time.

The lower dosage can be better for people who experience side effects with 50mg, or who have risk factors (like diabetes) that make them prone to side effects. On the other hand, a doctor may prescribe the 100mg tablet if you’ve tried 50mg and it wasn’t strong enough.

How often can you take Viagra?

The daily Viagra dosage depends on what you’ve been prescribed by your doctor, but you shouldn’t use Viagra more than once a day. However, there are other medications that can last longer (a whole weekend), or that you take every day (so that you’re ready to go whenever).

Blister strip of Sildenafil tablets
The (other) blue pill

Like Viagra, but cheaper.

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Does Viagra work?

Viagra is highly effective, working for approximately 3 in 4 men. Throughout clinical trials, 62% of men found that the 25mg dose gave them better erections, while 74% of men taking the 50mg dose reported improved erections. The 100mg dose also produced strong results, with 82% of men experiencing greater erectile potency.

How long does Viagra last?

The effects of Viagra normally last for up to 5 hours, but this can vary from one person to the next, so the best way to know how long it’s active for you is to try it.

Viagra duration also depends on a number of factors. If you’re over 65, you may find that it can last for longer than 5 hours as your body doesn’t remove it from your system as quickly as it once may have. Drinking alcohol reduces blood flow to the penis, which can make it more difficult to get an erection. And your Viagra pill might need some extra time to kick in if you eat a big meal that’s high in fat versus taking it on an empty stomach.

If you feel that the effects of Viagra are not lasting long enough, you should discuss your dose with your doctor.

Does Viagra work the first time?

Viagra works the first time (or the second) for most men who start on the 50mg dose.

Sometimes the 50mg dose can cause side effects such as a headache or feeling sick, and in these instances your doctor may recommend reducing your dose to 25mg.

On the other hand, if you find that the 50mg dose isn’t giving you a sustained erection for long enough, it’s worth speaking to your prescriber about increasing your dose to 100mg provided you haven’t had any side effects on the 50mg tablet.

Does Viagra make you bigger?

No, Viagra will not make your penis any bigger, and there aren’t any other tablets that can do this either.

However, Viagra does help you reach “peak size.” So while it doesn’t give you any extra length or girth, Viagra can make your erections as firm as possible.

It’s worth mentioning that any pills claiming to make your penis larger should be looked at with a lot of caution. It’s likely that they’re not licensed medications, and so could be dangerous.

What should I do if Viagra isn’t working?

If you find that Viagra doesn’t work, talk to your doctor about switching to a higher dose. But if you’ve already had your dose adjusted and that hasn’t improved things, it’s worth exploring different ED medications.

There are lots of ED products available with proven efficacy, and you may have to try a few different options before determining the right medication for you when Viagra doesn’t work.

Remember to only take Viagra or Viagra Connect as your clinician advises. If you have any questions while you're taking it, just log into your account and send us a message.

How does Viagra work?

Viagra and several other ED treatments are PDE5 inhibitors. PDE5 stands for Phosphodiesterase Type 5 and it’s an enzyme in the walls of your blood vessels. What happens when you take Viagra (and similar medications with the active ingredient sildenafil citrate) is that your blood vessels relax, so blood can get to where you need it most. Put simply, Viagra helps you get and maintain an erection. 

Is Viagra safe?

Viagra is quite safe and has undergone rigorous scientific testing before being approved to treat erectile dysfunction. That said, some men have reported side effects when taking Viagra. It’s important to know what these are before you start treatment, so make sure you read the leaflet that comes with the medicine.

It’s rare, but there are other medications that can interact with Viagra, including other ED treatments. You should provide the prescriber with a detailed medical history and information on any other medications you take, including vitamins and recreational drugs, so they can make sure Viagra is safe for you.

Like all medications, Viagra can eventually expire. The usual shelf life for sildenafil is around two years. So, if you come across any old medication, it’s probably best to get a new prescription. Old medication is likely to be less effective, and it’s even possible that it can grow mould or bacteria.

Store your Viagra out of direct sunlight and under 30°C so it stays safe and effective for as long as possible.

Does Viagra make you last longer?

There’s some evidence to suggest that Viagra can help with premature ejaculation. However, the evidence isn’t conclusive and Viagra isn’t prescribed to treat premature ejaculation.

Although most studies of Viagra and its main ingredient, sildenafil, have focused on its treatment of erectile dysfunction, there are two that looked at whether Viagra can delay ejaculation. The first study found that sildenafil is “very effective and safe to treat PE” and the second that sildenafil increased confidence, the perception of ejaculatory control and overall sexual satisfaction.

So while you won’t currently get a sildenafil prescription for premature ejaculation, it’s possible that the medication will help you if you experience PE as well as erectile dysfunction. If you’re interested in this potential effect, talk to the prescriber during your consultation and they can give you more information and advice.

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This page was medically reviewed by Dr Daniel Atkinson, GP Clinical Lead on August 02, 2022. Next review due on August 01, 2024.

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