Viagra (sildenafil)

Viagra (sildenafil)
Viagra tablets contain the active ingredient sildenafil, which is a medicine used in the treatment of erectile dysfunction (impotence). Sildenafil is also available without a brand name, ie as the generic medicine.
What is Viagra used for?
How does Viagra work?
Viagra tablets contain the active ingredient sildenafil, which is a medicine used in the treatment of erectile dysfunction (impotence). Sildenafil is also available without a brand name, ie as the generic medicine.
Sildenafil is called a phosphodiesterase type 5 inhibitor, and works by preventing the action of a chemical in the body called phosphodiesterase type 5.
An erection is produced via a complex chain of events, involving signals from the nervous system and the release of chemical messengers within the tissues of the penis. One of these chemical messengers is called cyclic GMP.
Cyclic GMP causes the blood vessels in the penis to widen by relaxing a thin layer of muscle found in the blood vessel walls. This allows more blood to enter the penis, which ultimately results in the penis becoming rigid and erect.
Cyclic GMP is normally broken down by another chemical in the body called phosphodiesterase type 5. Sildenafil works by preventing the action of phosphodiesterase type 5, thus stopping the breakdown of cyclic GMP. This means that the blood vessels are kept dilated for longer, improving blood flow to the penis and maintaining an erection.
As sildenafil enhances the actions of the chemical messengers responsible for producing an erection, it will only work once these messengers are present. This means that sexual stimulation is required for it to produce and maintain an erection. The dose should be taken approximately one hour before you intend to have sex.
How do I take Viagra?
Viagra tablets should preferably be taken on an empty stomach. If they are taken with food they may take longer to start working. Your tablet should be swallowed whole with a drink of water. Your Viagra tablet should be taken about one hour before sexual activity. With sexual stimulation you may achieve an erection after about 30 to 60 minutes. You should avoid drinking grapefruit juice while taking this medicine, as it may increase the level of this medicine in your blood and hence increase the risk of side effects. You should not take Viagra more than once a day.
This medicine may cause dizziness and visual disturbances. You should make sure you are aware of your reactions to this medicine before driving or operating machinery. If you do feel dizzy or lightheaded after taking this medicine you should lie down until the symptoms pass. If your erection lasts longer than four hours (priapism), consult a doctor immediately. Treatment of this condition should not be delayed more than six hours, as this can cause damage to the erectile tissue in the penis and irreversible erectile dysfunction. If you experience a sudden decrease or loss of vision, stop taking this medicine and contact your doctor immediately.
Use with caution in.
Elderly people. Decreased kidney function. Decreased liver function. Disease involving the heart and blood vessels (cardiovascular disease). People with any obstruction of blood flow out of the heart, eg due to narrowing of the aorta (aortic stenosis). Bleeding disorders, eg haemophilia. People with an active peptic ulcer. Conditions such as sickle cell disease, bone cancer or leukaemia in which there is an increased risk of prolonged erections (priapism). Men with a physical abnormality of the penis, such as severe curvature, scarring or Peyronie’s disease.
Who shouldn’t take Viagra?
Women. Children or adolescents under 18 years of age. People who have conditions in which sexual activity is not advisable, for example severe heart disorders such as unstable angina or severe heart failure. People who have recently had a heart attack. People who have recently had a stroke. People with low blood pressure (hypotension). People taking any form of nitrate medications, eg glyceryl trinitrate or amyl nitrite “poppers” (see end of factsheet for more examples). People with severely decreased liver function. People with hereditary degeneration of the back of the eyeball (retina), such as retinitis pigmentosa. People who have ever experienced an eye condition called non-arteritic anterior ischemic optic neuropathy (NAION). This condition causes a sudden, partial decrease or loss of vision in one or both eyes due to damage to the optic nerve. It can be temporary or permanent. Tell your doctor if you have ever experienced this. People who are allergic to any ingredients of the medicine. Check the ingredients listed in the leaflet that comes with the medicine if you know you have specific allergies or intolerances.
What are the possible side effects of Viagra?
Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects associated with sildenafil. Just because a side effect is stated here doesn’t mean that all people taking Viagra will experience that or any side effect.
Very common (affect more than 1 in 10 people)
Common (affect between 1 in 10 and 1 in 100 people)
Dizziness. Visual disturbances, such as blurred vision, blue tinge to vision. Flushing. Nasal congestion. Indigestion.
Uncommon (affect between 1 in 100 and 1 in 1000 people)
Awareness of your heart beat (palpitations). Increased heart rate (tachycardia). Chest pain. Muscle pain. Sleepiness or fatigue. Decreased sensation of the body to normal stimulation such as touch or pain. Sensation of spinning. Sensation of ringing or other noise in the ears (tinnitus). Feeling sick or vomiting. Dry mouth. Rash. Eye disorders such as bleeding at the back of the eye, bloodshot eyes/red eyes, eye pain, double vision, abnormal sensation in the eye.
Rare (affect between 1 in 1000 and 1 in 10,000 people)
Increased or decreased blood pressure. Sudden decrease or loss of hearing. Nosebleeds. Fainting. Stroke (cerebrovascular accident).
Frequency not known.
Prolonged erection, or persistent painful erection of the penis (priapism). Seizure. Mini-stroke (transient ischaemic attack). Unstable angina. Abnormal heart beats (arrhythmias). Severe allergic blistering skin reaction (Stevens-Johnson syndrome). Severe flaking of the surface layer of the skin (toxic epidermal necrolysis). Sudden death due to heart attack.
Read the leaflet that comes with the medicine or talk to your doctor, nurse or pharmacist if you want any more information about the possible side effects of Viagra. If you think you have experienced a side effect, did you know you can report this using the yellow card website ?
Can I take Viagra with other medicines?
It is important to tell your doctor or pharmacist what medicines you are already taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Similarly, check with your doctor or pharmacist before taking any new medicines while taking this one, to make sure that the combination is safe.
Sildenafil must not be taken with any form of nitrate medication, as this combination can produce a severe drop in blood pressure that can cause dizziness, fainting, or even a heart attack. Nitrate medications include the following:
glyceryl trinitrate , isosorbide mononitrate and isosorbide dinitrate (used for angina or heart failure – if you experience chest pain after taking this medicine DO NOT use nitrates to treat it) nicorandil amyl nitrate (also known as ‘poppers’).
Sildenafil should be used with caution in people who are taking alpha-blocker medicines, as the combination may increase the risk of a drop in blood pressure, which may cause dizziness or fainting. This is most likely to occur within four hours of taking the sildenafil. Alpha-blockers include the following:
If you are taking an alpha-blocker medicine your doctor will probably start you on a 25mg dose of sildenafil. If you feel dizzy or light-headed after taking the sildenafil you should lie down until the symptoms pass.
Sildenafil should not be taken with other treatments for erectile dysfunction, as the safety of such combinations have not been established.
The following medicines may increase the blood level of sildenafil and you may need a lower sildenafil dose if you are taking any of these:
The HIV protease inhibitor ritonavir can cause a large increase in the blood level of sildenafil. Sildenafil is not recommended for people taking ritonavir , however, if it is used, the maximum dose of sildenafil should under no circumstances exceed 25mg within 48 hours.
What other medicines contain sildenafil?
Nipatra chewable tablets. Vizarsin tablets.
Sildenafil tablets are also available without a brand name, ie as the generic medicine.
Last updated 26.06.2013.
B e in f o r m ed. L i v e w e ll.
The materials in this web site are in no way intended to replace the professional medical care, advice, diagnosis or treatment of a doctor. The web site does not have answers to all problems. Answers to specific problems may not apply to everyone. If you notice medical symptoms or feel ill, you should consult your doctor – for further information see our Terms and conditions.
NetDoctor is a publication of Hearst Magazines UK which is the trading name of The National Magazine Company Ltd, 72 Broadwick Street, London, W1F 9EP. Registered in England 112955. All rights reserved. NetDoctor, part of the Hearst UK wellbeing network. Copyright © 2017.