Sildenafil Product Information
Sildenafil is used to help men who have trouble achieving or maintaining their erection. Its active ingredient sildenafil belongs to a group of medications known as phosphodiesterase type 5 inhibitors (PDE5). Sildenafil helps relax the blood vessels in the penis, which, in the presence of sexual stimulation, allows blood to flow into the penis and helps with achieving or maintaining an erection.
Sildenafil (Viagra) works by inhibiting the action of a chemical called Phosphodiesterase type-5 (PDE5). When released by the body, PDE5 contributes to the loss of an erection by causing a reduction in blood flow to the penis. Sildenafil (Viagra) works by blocking the effect of PDE5 to increase blood flow, helping the patient to achieve an erection and maintain it for longer.
The recommended starting dose is 50mg of the treatment once a day maximum (24 hours). For optimal effectiveness, consume Sildenafil whole with water on an empty stomach, one hour before engaging in sexual activity. Consuming food before taking the medication can delay absorption, resulting in it taking longer to work. Eating an hour after taking the pill will not affect its activity.
Sildenafil takes approximately 1 hour to work. It will not work without sexual stimulation.
Sildenafil works with sexual stimulation and its effects can last about four hours. This does not mean that you will have an erection for four hours, but rather that you have the potential for an improved erection as long as the drug lasts in your body.
You can buy Sildenafil from some UK pharmacies after a consultation with the pharmacist. However, not all pharmacists and pharmacies offer this service.
Watch our patient care expert explain everything you need to know about Sildenafil.
Sildenafil FAQs
Sildenafil Citrate is the active ingredient found in the erectile dysfunction medication Viagra. Since Pfizer’s patent on Sildenafil expired, other manufacturers have been able to produce a generic form of the medication which is generally available at a much lower cost. Sildenafil is available in three strengths: 25mg, 50mg and 100mg.
For most men, Sildenafil (Viagra) remains effective in the body for up to four hours. Sildenafil (Viagra) will reach peak effectiveness around thirty minutes after taking the tablet and usually last for up to four hours before the effectiveness starts to diminish.
Sildenafil (Viagra) is a medication primarily used to treat erectile dysfunction. Erectile dysfunction can be caused by a problem with one of the many complex biological or psychological processes responsible for achieving and maintaining an erection. Sildenafil (Viagra) is used to treat erectile dysfunction by increasing blood flow to the penis during sexual arousal.
Sildenafil (Viagra) starts to work in the body after just 30 minutes. Sildenafil (Viagra) can take longer to work if the tablet has been taken with food. For Sildenafil (Viagra) to work and cause the patient to get an erection, they will need to be sexually aroused.
Viagra contains the active ingredient Sildenafil Citrate. Viagra is produced by the pharmaceutical company Pfizer. The generic Sildenafil has been available for alternative manufacturers to produce since the Pfizer patent for Viagra expired. Medically, Sildenafil and Viagra are equivalent as they both contain Sildenafil Citrate, however, the excipients used to formulate the tablets may differ.
You should not take Sildenafil with any other PDE5 inhibitor unless specifically instructed by your doctor. If you would like to try different ED medications, you can do as long as only 1 tablet is taken in a 24 hour period. You can see our specially priced ED Trial Packs here
Originally, Sildenafil was manufactured under the brand name of Viagra by the company Pfizer. Sildenafil is now able to be manufactured by other companies as the original product patent by Pfizer has now expired. There are many manufacturers that currently produce Sildenafil to be sold in the UK market.
Sildenafil (Viagra) is used to treat erectile dysfunction (ED) and will not directly help with premature ejaculation (PE). An alternative medication that has been proven to help with premature ejaculation is Dapoxetine (Priligy), which can be found here.
Taking Sildenafil (Viagra) with alcohol is not recommended for a number of reasons. Taking Sildenafil (Viagra) with alcohol can increase your risk of experiencing side effects, it could also adversely affect your ability to achieve and maintain an erection.
Sildenafil (Viagra) is not intended for use as a daily medication. Sildenafil (Viagra) has an effective time frame of four hours and should be taken as and when required, at least thirty minutes before intercourse. For a longer lasting daily effect, Tadalafil (Cialis) is available in a daily dose and is equally as effective as Sildenafil (Viagra) or Sildenafil (Viagra Connect).
Sildenafil (Generic Viagra) Overview
| Sildenafil (Generic Viagra) |
|---|
| Strength
| 25 mg
50 mg
100 mg |
| How long it lasts
| Up to 4 hours |
| Dosage
| One tablet an hour before |
| How fast it works
| 30 - 60 minutes |
| Active Ingredient
| Sildenafil |
Common Side Effects
- pain in your back/muscles/head
- migraines
- getting flushed/going red
- indigestion
- feeling and or being sick
- getting a blocked or runny nose
- vision disturbances
Reporting side effects
This is not a complete list of side effects. Always read the Patient Information Leaflet supplied with your medication.
You can report suspected side effects directly through the MHRA Yellow Card Scheme. You can also tell our team, who can report on your behalf.
Information Leaflet
Always read the patient information leaflet before commencing treatment.
Important: We advise you to always read the patient information leaflet inside the medication box, as the generic medication may not always entirely match the patient information leaflet listed. Please contact us if you have any questions.
Written and reviewed by our qualified team
Content last updated:
13 Aug 2026