Sildenafil – all you need to know

What is Sildenafil? And what is it used for?

Sildenafil is a treatment for adult men with erectile dysfunction – sometimes known as impotence. It belongs to a group of medicines called phosphodiesterase type 5 (PDE 5) inhibitors.
It works by helping to relax the blood vessels in your penis, allowing blood to flow into your penis when you get sexually excited. Sildenafil will only help you to get an erection if you are sexually stimulated. 

What you need to know before you take Sildenafil

Do not take Sildenafil if:

  • You are allergic to Sildenafil or any of the other ingredients of this medicine.
  • You are taking medicines called nitrates, as the combination may lead to a dangerous fall in your blood pressure. Indicate in your online questionnaire if you are taking any of these medicines which are often given for relief of angina pectoris (or “chest pain”). If you are not certain, ask a doctor or pharmacist.
  • You are using any of the medicines known as nitric oxide donors such as amyl nitrite (“poppers”) as the combination may also lead to a dangerous fall in your blood pressure.
  • You have a severe heart or liver problem.
  • You have recently had a stroke or a heart attack, or if you have low blood pressure.
  • You have certain rare inherited eye diseases (such as retinitis pigmentosa).
  • You have ever had loss of vision due to non-arteritic anterior ischaemic optic neuropathy (NAION).
Warnings and precautions

State on your consultation if:

  • You have sickle cell anaemia (an abnormality of red blood cells).
  • Leukaemia (cancer of blood cells).
  • Multiple myeloma (cancer of bone marrow).
  • If you have a deformity of your penis or Peyronie’s Disease.
  • You have problems with your heart. Your doctor should in that case carefully check whether your heart can take the additional strain of having sex.
  • You currently have a stomach ulcer, or a bleeding problem (such as haemophilia).
  • You experience sudden decrease or loss of vision – stop taking Sildenafil and contact your doctor immediately.
    You should not use Sildenafil:
  • With any other oral or local treatments for erectile dysfunction.
  • With treatments for pulmonary arterial hypertension (PAH) containing Sildenafil or any other PDE5 inhibitors.
  • If you do not have erectile dysfunction.
  • If you are a woman.

Children and adolescents

Sildenafil should not be given to individuals under the age of 18.


Special considerations for patients with kidney or liver problems

You should mention in your consultation if you have kidney or liver problems. Your doctor may decide on a lower dose for you.


Sildenafil with food, drink and alcohol

Sildenafil can be taken with or without food. However, you may find that Sildenafil takes longer to start working if you take it with a heavy meal.
Drinking alcohol can temporarily impair your ability to get an erection. To get the maximum benefit from your medicine, you are advised NOT to drink excessive amounts of alcohol before taking Sildenafil.

Pregnancy, breast-feeding and fertility

Sildenafil is not indicated for use by women.

Driving and using machines

Sildenafil can cause dizziness and can affect vision. You should be aware of how you react to Sildenafil before you drive or use machinery.

Sildenafil contains lactose

Sildenafil film-coated tablets contain lactose monohydrate. If you have been told by your doctor that you have an intolerance to some sugars, such as lactose, state in your online consultation before placing an order.

How to take Sildenafil

Always take this medicine exactly as it has been prescribed to you. You should not take Sildenafil more than once a day.

Do not take Sildenafil film-coated tablets in combination with Sildenafil orodispersible tablets. You should take Sildenafil about one hour before you plan to have sex. Swallow the tablet whole with a glass of water.

Sildenafil will only help you to get an erection if you are sexually stimulated.

The amount of time Sildenafil takes to work varies from person to person, but it normally takes between half an hour and one hour. You may find that Sildenafil takes longer to work if you take it with a heavy meal. If Sildenafil does not help you to get an erection, or if your erection does not last long enough for you to complete sexual intercourse, you should tell your doctor.

If you take more Sildenafil than you should

You may experience an increase in side effects and their severity. Doses above 100 mg do not increase the efficacy. You should not take more tablets than has been prescribed for you.

Possible side effects

Like all medicines, Sildenafil can cause side effects – although not everybody gets them. The side effects reported in association with the use of Sildenafil are usually mild-to-moderate and of a short duration.
However, if you experience any of the following serious side effects, stop taking Sildenafil and seek medical help immediately:

  • An allergic reaction – this occurs uncommonly (may affect up to 1 in 100 people). Symptoms include sudden wheeziness, difficulty in breathing or dizziness, swelling of the eyelids, face, lips or throat.
  • Chest pains (this occurs uncommonly). If this occurs during or after intercourse: get in a semi-sitting position and try to relax; do not use nitrates to treat your chest pain.
  • Prolonged and sometimes painful erections – this occurs rarely (may affect up to 1 in 1,000 people). If you have an erection that lasts for more than four hours, you should contact a doctor immediately.
  • A sudden decrease or loss of vision – this occurs rarely.
  • Serious skin reactions – this occurs rarely. Symptoms may include: severe peeling and swelling of the skin; blistering of the mouth, genitals and around the eyes; fever.
  • Seizures or fits – this is a rare occurrence.

Other side effects

Very common (may affect more than 1 in 10 people)
Common (may affect up to 1 in 10 people)
Nausea, facial flushing, hot flush (symptoms include a sudden feeling of heat in your upper body), indigestion, colour tinge to vision, blurred vision, visual disturbance, stuffy nose and dizziness.
Uncommon (may affect up to 1 in 100 people)
Vomiting, skin rash, eye irritation, bloodshot eyes/red eyes, eye pain, seeing flashes of light, visual brightness, light sensitivity, watery eyes, pounding heartbeat, rapid heartbeat, high blood pressure, low blood pressure, muscle pain, feeling sleepy, reduced sense of touch, vertigo, ringing in the ears, dry mouth, blocked or stuffy sinuses, inflammation of the lining of the nose (symptoms include runny nose, sneezing and stuffy nose), upper abdominal pain, gastro-oesophageal reflux disease (symptoms include heartburn), presence of blood in urine, pain in the arms or legs, nosebleed, feeling hot and feeling tired.
Rare (may affect up to 1 in 1000 people)
Fainting, stroke, heart attack, irregular heartbeat, temporary decreased blood flow to parts of the brain, feeling of tightening of the throat, numb mouth, bleeding at the back of the eye, double vision, reduced sharpness of vision, abnormal sensation in the eye, swelling of the eye or eyelid, small particles or spots in your vision, seeing halos around lights, dilation of the pupil of the eye, discolouration of the white of the eye, penile bleeding, presence of blood in semen, dry nose, swelling of the inside of the nose, feeling irritable and sudden decrease or loss of hearing.

Join the club.

Enter your email address. We’ll make sure you’re the first to know when we go live! We’ll also send you discounts and occasional advice.

By submitting your email address, you agree to be contacted by Betterman and to be added to our database as per our terms & conditions.