What is sildenafil?
Sildenafil (also branded as Viagra) is a treatment for erectile dysfunction (ED). It’s a ‘phosphodiesterase‑5 (PDE‑5) inhibitor’ that temporarily relaxes the blood vessels that supply your penis. This helps you to get and keep an erection when you’re sexually aroused.
Often referred to as ‘generic viagra’, sildenafil must meet the same UK quality standards as Viagra, yet usually costs less.
Sildenafil uses include the treatment of pulmonary hypertension, where it can help lower blood pressure in the blood vessels that supply your lungs
How does sildenafil work?
Sildenafil is a ‘PDE‑5 inhibitor’. It works by stopping the action of a chemical in your body called phosphodiesterase type-5. This helps to relax blood vessels, widening them to improve blood flow to your penis when you get aroused and help maintain an erection.
How sildenafil works
| Releasing the relaxation chemical cGMP | Boosting blood flow by stopping the PDE-5 enzyme |
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While sildenafil pills are used for ED to help you get and maintain an erection, no sildenafil dosage can resolve the underlying physical cause of your erectile dysfunction or increase your sexual desire.
How long does it take for sildenafil to take effect?
Most men notice results within 30-60 minutes of taking a sildenafil tablet. You can take it with or without food but you may find it works more slowly if taken with a heavy or high‑fat meal. Don’t forget, you need to be aroused for sildenafil to work.
How long does Sildenafil last?
Sildenafil can take 60 minutes on average to reach maximum plasma concentration, but the patient should be able to still produce an erection 4-5 hours post after they have taken their dose. This doesn’t mean a continuous erection for that period, but rather it’s easier to get one within that window.
How effective is sildenafil?
In fixed dose studies, 74% of men reported improved erections on 50mg of sildenafil (compared to 25% on a placebo). If it’s your first-time taking sildenafil, there’s a chance it might not work. We recommend you try an ED medication up to 8 times on separate occasions before considering a higher dose or looking for an alternative.
If you’ve eaten a large meal you may find sildenafil is less effective. Similarly, with sildenafil and alcohol, too many drinks can reduce its effectiveness.
Whether you’re getting started with 25mg sildenafil pills, or you need sildenafil 50mg or 100mg tablets, our service makes ordering easy and discreet.
Who can take sildenafil tablets?
Most men over the age of 18 can take sildenafil. However, you can't take sildenafil if:
- You're a woman
- You're taking nicorandil or nitrates (for chest pain) such as GTN spray
- You're taking isosorbide mononitrate tablets to treat angina
- You have a serious liver or heart problem
- You've recently had a stroke, heart attack or other heart problem
- You have low blood sugar (hypotension)
If you’re taking alpha-blockers such as doxazosin or tamsulosin, you should wait at least 6 hours between having your dose of those and taking sildenafil.
It is important to let our clinicians know which prescription, over-the-counter medicines and recreational drugs you are taking so that we can prescribe Sildenafil safely.
Always get sildenafil online from a UK regulated and certified Online Doctor erectile dysfunction service like ours. Start a confidential consultation now, and if you’re medically suitable, our clinicians can prescribe sildenafil tablets for you.
How to take sildenafil tablets
You should only take sildenafil once a day. Take one tablet 30-60 minutes before sex. Never take more than one Sildenafil tablet in 24 hours. Sildenafil works best on an empty stomach.
Can I take sildenafil daily?
You take one sildenafil tablet about an hour before you plan to have sex, and it can remain effective for between 4 and 6 hours when you get aroused. It’s not intended for continuous daily use.
Can you take sildenafil alongside other ED medication?
Do not combine sildenafil alongside other ED medication.
As there are several options available for erectile dysfunction treatments available, it can be tempting to combine two (like sildenafil and tadalafil) together to increase your chances of a successful erection.
You must not do this.
Combining ED treatments can lead to side effects like dangerously low blood pressure and fainting. If you’re not getting the right results from your current erectile dysfunction treatment, speak to your GP or clinician before changing treatment.
Are sildenafil tablets and sildenafil suspension interchangeable?
An oral sildenafil suspension delivers the same active ingredient and is sometimes used for patients with swallowing difficulties. Four pumps of a suspension like Hezkue provides 50mg of sildenafil, the same you would find in a standard dose pill. Only switch to a sildenafil suspension if advised by your doctor, a clinician or a pharmacist and always check the medicine label
Sildenafil dosage
There are three dosages of sildenafil: 25mg, 50mg and 100mg. The treatment is currently available as:
| Dosage / Tablet amount | 4 tablets | 8 tablets | 16 tablets |
| 25mg | £16.00 | £24.00 | £45.00 |
| 50mg | £15.00 | £28.00 | £44.99 |
| 100mg | £25.00 | £35.00 | £60.00 |
| Dosage / Tablet amount | 4 tablets | 8 tablets | 16 tablets |
| 50mg | £12.75/month | £23.80/month | £38.24/month |
| 100mg | £21.25/month | £29.00/month | £51.00/month |
The standard sildenafil dose is 50mg. Depending on your age, height and weight, the cause and the severity of your ED, you may be prescribed a lower dose of 25mg, or a higher one of 100mg. It’s okay to take 100mg of sildenafil if your clinician prescribes it, but higher doses come with an increased chance of sildenafil side effects in males.
Sildenafil dosage does not affect how quickly or for how long the treatment works. You should take Sildenafil tablets in the dosage suggested by your clinician or as explained in the patient information leaflet.
“You may be tempted to choose the highest dosage of Sildenafil to guarantee an erection, but that doesn’t guarantee results. Consult your GP or take one of our online consultations to determine the correct dosage for you. It is recommended you try your current dosage eight times to determine its effectiveness. If there’s been little to no effect after that, talk to your GP about changing dosages.” - Dr Bhavini Shah
Sildenafil side effects
Like all medicines, sildenafil can cause side effects. However not everyone will experience these and they tend to be mild and last only a short time. Side effects of sildenafil can include:
- Nausea
- Vomiting
- Back pain
- Diarrhoea
- An allergic rash
- Facial flushing
- Headaches
- Light headedness
- Nasal congestion
- Indigestion
- Palpitations (racing heartbeat)
Find out more about sildenafil and blood pressure in the FAQs below. For full information on side effects and correct use, see the patient information leaflet.
Long-term side effects of sildenafil
According to NHS advice, there do not seem to be any lasting harmful effects from long term use.
Alternative treatments to sildenafil
If you’d like to know your alternatives to sildenafil because it hasn’t worked for you, contact us through your Account and we can talk you through more ED treatment options. Here’s a summary of our ED treatments:
| Name | Cialis | Levitra | Spedra | Vitaros |
| Active Ingredient | Tadalafil | Vardenafil | Avanafil | Alprostadil |
| How long to take effect | 30-60 minutes | Within an hour | 60 minutes | 5-30 minutes |
| How long does it last? | Up to 36 hours | Up to 5 hours | Up to 4 hours | Up to 2 hours |
| Effectiveness | Works for up to 80% of men | Works for up to 87% of men | Works for up to 58% of men | Works for up to 52% of men |
