Sildenafil (Viagra)

Most people have heard of Viagra which is commonly used to treat erectile dysfunction. Viagra works by blocking the action of a chemical within the body called ‘ phosphodiesterase type 5’.

How does that relate to an erection?

An erection occurs due to a complex set of signals via the brain and nervous system, and the release of chemical agents within the tissues of the penis. One of these chemical agents is ‘ cyclic GMP’ which is responsible for widening the blood vessels within the penis.

It does this by opening and relaxing a slim layer of muscle within the walls of the blood vessels. This enables a greater flow of blood into the penis which causes it to become stiff and erect.

Cyclic GMP is normally broken down by phosphodiesterase type 5. But, Viagra prevents this from happening which enables the blood vessels to remain dilated for much longer, thereby increasing blood flow and sustaining an erection.

Viagra is effective at boosting these chemical messengers, such as cyclic GMP as long as they are present. So, sexual stimulation will still be required.

Viagra dosage

Viagra should be taken one hour before sexual intercourse, but, the effects will take longer to appear if it is taken with food. So, take it on an empty stomach. Do not take it with grapefruit juice as this can increase the risk of side effects.

Viagra effects

The effects of Viagra last for around 4 hours and tend to work ‘ on demand’: in other words, when you need them to work.

Viagra caution

Viagra is to be used with caution in the following cases:

• Cardiovascular disease
• Decreased liver/kidney function
• Obstructed blood flow away from the heart e.g. aortic stenosis
• Blood clotting disorders, e.g. haemophilia
• Active peptic ulcer
• Physical abnormality of the penis, e.g. Peyronie’s disease
• Bone cancer
• Leukaemia
• Sickle cell disease
• Elderly people

If you experience an erection which last for more than 4 hours then seek urgent medical advice as this may be a symptom of priapism. Plus there is the danger of permanent damage to the tissue within the penis.

Viagra can cause you to feel dizzy, light headed or nauseous. If you experience any of these symptoms then lie down until they ease. Avoid driving or operating any machinery if possible until they have eased.

Do not take Viagra more than once a day.

Viagra avoidance

Viagra must not be taken by any of the following:

• Women
• Teenagers under 18
• People with low blood pressure (hypotension)
• People who have suffered a stroke
• People who have suffered a heart attack
• Unstable angina or severe heart failure
• People with severely decreased liver function
• Degenerative eye conditions such as retinitis pigmentosa
• People who are taking any types of nitrate medications, such as amyl nitrate ( ‘ poppers’) or glyceryl trinitrate.
• People who have ever suffered from an eye condition called ‘ non-arteritic ischemic optic neuropathy (NAION).
• People with rare hereditary problems of lactose intolerance, e.g. galactose intolerance or Lapp lactase deficiency. Note: Viagra tablets contain lactose.

Plus if you experience an allergic reaction to Viagra or to any of its ingredients then stop taking this and speak to your GP as soon as possible.

Viagra side effects

Every form of medication can cause side effects but not everyone is affected to the same degree. Some people will experience mild effects whereas others have a severe reaction. All medicines affect people in different ways.

Viagra is no different.

Viagra can cause a variety of side effects which range from common through to very rare. These include:

• Headaches
• Flushes
• Nasal congestion
• Indigestion
• Dizziness
• Blurred vision etc

Headaches are a very common side effect whereas the other effects occur but less often.

Then there are uncommon or rare side effects which include:

• Nausea and/or vomiting
• Heart palpitations
• Chest pain
• Muscle pains
• Skin rash
• Fatigue
• Tinnitus (ringing in the ears)
• Dry mouth
• Arrhythmias (abnormal heart beats)
• High or low blood pressure
• Nose bleeds
• Fainting
• Stroke
• Heart attack

There have been a few cases of priapism “ prolonged erection of the penis but these are very rare.

If you are taking any other form of medication such as alpha-blockers (used to treat high blood pressure), nitrate medicines, over the counter medicines or herbal remedies then speak to your GP.

It is important that you check with your GP first to see if it is safe for you to take a combination of drugs.

Mention to him/her if you thinking of taking a new form of medication as well as your erectile dysfunction medication. Do this before you take any cocktail of drugs.