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Manufactured by various MHRA-approved generic manufacturers


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What to do if you missed your sildenafil dose

Report suspected side effects or adverse reactions to the Medicines and Healthcare Products Regulatory Agency (MHRA) using the Yellow Card Reporting system that covers medicines, vaccines, e-cigarettes and medical device incidents.

Learn more about reporting side effects

Other known brand names

Viagra, Aronix, Liberize, Nipatra, Revatio, Grandipam

About sildenafil

Sildenafil citrate is commonly prescribed to treat the condition erectile dysfunction. Sildenafil belongs to a group of medicines called phosphodiesterase type 5 (PDE5) inhibitors. It works by temporarily increasing the blood flow to the penis, during periods of sexual stimulation. It is available with a prescription as generic sildenafil or under brand names Viagra, Liverize, Nipatra and Aronix. It is also available as the brand Viagra Connect, over the counter.

Sildenafil in certain doses is also used to treat pulmonary arterial hypertension (high blood pressure affecting blood vessels supplying the lungs) by relaxing blood vessels in the chest. It is available with a prescription under the brand names Revatio or Grandipam.

NowPatient offers sildenafil or the brand Viagra as treatments for erectile dysfunction only, following an online consultation with a prescribing clinician.

Key facts of sildenafil

  • For the treatment of erectile dysfunction, sildenafil usually takes 30 to 60 minutes to work
  • Sildenafil can be taken up to 4 hours before you want to have sex
  • Sildenafil does not result in an erection if taken alone. You would need to be sexually excited for it to work
  • Sildenafil has some common side effects which include headaches, feeling sick, indigestion and dizziness. Many people display no side effects or if they do the side effects can be mild
  • It can be dangerous if you take sildenafil with certain medications like alpha blockers or nitrates (nitroglycerin, isosorbide). The combination of use can lead to a dangerous fall in your blood pressure. If you’re not sure if you’re taking a nitrate, you can discuss this with the prescribing clinician
  • You should avoid drinking grapefruit juice if you’re taking sildenafil (Revatio) prescribed for pulmonary hypertension because It affects the way the medicine works

Who is sildenafil suitable for?

Sildenafil is suitable for most men aged 18 and over for erectile dysfunction.

Who is sildenafil not suitable for?

Sildenafil may not be suitable for some people. To make sure it’s safe for you, speak to the prescribing clinician before taking sildenafil if you:

  • Have low blood pressure (hypotension)
  • Have a rare inherited eye disease, such as retinitis pigmentosa
  • Have sickle cell anaemia (an abnormality of red blood cells), leukaemia (cancer of blood cells) or multiple myeloma (cancer of bone marrow)
  • Have a deformity of your penis or Peyronie’s disease (curved penis)
  • Have a stomach ulcer
  • Have a bleeding problem like haemophilia
  • Have ever had an allergic reaction to sildenafil or any other medicine
  • Are taking medicines called nitrates for chest pain (angina)
  • Have a serious heart or liver problem
  • Have recently had a stroke, heart attack or a heart problem – your healthcare professional should carefully check whether your heart can take the additional strain of having sex

How and where to get sildenafil?

Sildenafil tablets are available from a number of sources. It is available on prescription or over the counter at a pharmacy.

NowPatient does not allow customers to buy sildenafil directly. Our service is certified, safe and effective, and we only ever treat conditions. If you book a consultation with a prescribing clinician for the treatment of erectile dysfunction, you can discuss if sildenafil is a suitable treatment option for you.

At the end of the consultation, the clinician will decide if a treatment plan is suitable for you. If it is, the clinician will issue you with a prescription which can then be ordered, paid for and delivered directly to your chosen address by NowPatient.

Dosage and strength for sildenafil when used for erectile dysfunction

Sildenafil is available in tablet form and when used for erectile dysfunction, it is available in strengths ranging from 25mg to 100mg. The typical dose of sildenafil is 50mg, taken up to 4 hours before sexual activity. Do not take it more than once a day. This dose can be adjusted up to 100mg or decreased to 25mg depending on the effects.

Remember, for sildenafil to work properly, you will need to be sexually excited.

Information about how to take sildenafil for erectile dysfunction

Tablets should be swallowed whole with a drink of water or juice (avoid grapefruit juice). For erectile dysfunction, it is best to take sildenafil on an empty stomach. Sildenafil may take longer to work if you take it with a high-fat meal. Read the patient information leaflet provided to you with your medication.

What happens if you take too much sildenafil?

If you take more than prescribed, then it can lead to some unpleasant side effects.

You should talk to your doctor or reach out to one of our prescribing clinicians, if you have taken too much sildenafil and you experience any of the following side effects:

  • Headaches
  • Lightheadedness and dizziness
  • Indigestion
  • Nasal congestion
  • Hearing loss
  • Blurred vision

What are the side effects of sildenafil?

Side effects of sildenafil are split into common and serious.

If you are prescribed sildenafil for the treatment of erectile dysfunction, you’re unlikely to get side effects, since you are only taking it short term.

Common side effects include:

  • Headaches
  • Feeling sick (nausea)
  • Flushing including hot flushes
  • Indigestion
  • Stuffy nose
  • Feeling dizzy

Serious side effects include:

  • Sudden decrease or loss of vision
  • Serious allergic reaction
  • Priapism (long-lasting and potentially painful erection)
  • Heart attack, stroke, or irregular heartbeat, which mainly occur in people with heart disease

If you experience any serious side effects, you should contact NHS 111.

If you experience a serious allergic reaction with the signs shown below you should contact emergency services on 999.

  • Your lips, mouth, throat or tongue suddenly become swollen
  • You’re breathing very fast or struggling to breathe (you may become very wheezy or feel like you’re choking or gasping for air)
  • Your throat feels tight or you’re struggling to swallow
  • Your skin, tongue or lips turn blue, grey or pale (if you have black or brown skin, this may be easier to see on the palms of your hands or soles of your feet)
  • You suddenly become very confused, drowsy or dizzy
  • Someone faints and cannot be woken up

Always report adverse effects to the MHRA yellow card reporting system. You can read more about this here: How do i report side effects of my medicaidon – NowPatient 

Information about taking sildenafil at the same time as other medications or herbal supplements

You should inform your doctor or prescribing clinician if you are currently taking any medications called nitrates.

There is not enough evidence to suggest there are any drug interactions between herbal supplements and sildenafil. In any event, you should let your prescribing clinician know if you are taking any herbal supplements.

Why might sildenafil not work for erection problems?

Sildenafil may not work for you and common reasons may be:

  • You have not waited long enough after taking it before trying to have sex
  • You have waited too long after taking it to have sex
  • The dose is not high enough
  • You’re not sexually aroused

Can sildenafil taken for erectile dysfunction be taken long term?

Sildenafil is safe to take for a long time. There do not seem to be any lasting harmful effects from taking it for many months and years.

Is there a herbal sildenafil?

No. Herbal sildenafil does not exist. If you have been marketed such a formulation, it may be fake.

Can women use sildenafil?

Women can only take sildenafil for the treatment of pulmonary hypertension. Sildenafil is not licensed for use by women.

Should I avoid any particular food or drink when taking sildenafil?

You can eat and drink normally when taking sildenafil to get an erection.

What lifestyle changes can I make to help me with erectile dysfunction?

You modify your lifestyle in a number of ways, and this may have a positive impact on your erectile dysfunction.

  • Maintaining a healthy weight
  • Quitting smoking
  • Cutting down on the amount of alcohol you drink
  • Not taking recreational drugs
  • Exercising regularly
  • Reducing stress

Alternatives to sildenafil

Alternative PDE5 inhibitors for the treatment of erectile dysfunction include tadalafil (Cialis), and vardenafil (Levitra).


Medical Disclaimer

NowPatient has taken all reasonable steps to ensure that all material is factually accurate, complete, and current. However, the knowledge and experience of a qualified healthcare professional should always be sought after instead of using the information on this page. Before taking any drug, you should always speak to your doctor or another qualified healthcare provider.

The information provided here about medications is subject to change and is not meant to include all uses, precautions, warnings, directions, drug interactions, allergic reactions, or negative effects. The absence of warnings or other information for a particular medication does not imply that the medication or medication combination is appropriate for all patients or for all possible purposes.

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