What are these drugs?
Sildenafil, and the newer agents avanafil, tadalafil and vardenafil, work by using the body’s natural mechanism to control erection. They inhibit the naturally-occurring enzyme, phosphodiesterase, which ‘turns off’ an erection, thereby allowing an erection to be achieved and maintained more easily. Consult the patient information leaflet with your medicine for further information.
What are they used for?
- These drugs are only licensed for use in men with erectile dysfunction (impotence).
- They are not recommended for men with normal erections who simply wish to improve their sexual performance.
- They are not licensed for use in female sexual dysfunction.
- The drugs have no effect on sexual desire (libido), ejaculation or fertility.
What do they do?
These drugs augment an existing erection that has to be achieved by normal sexual stimulation. The drugs do not produce erections in their own right. Sexual stimulation, therefore, is an essential part of the process when these drugs are taken.
How should they be taken?
These drugs should be taken by mouth approximately one hour before anticipated sexual intercourse. The maximum recommended frequency is once per day but treatment can be continued for long periods (in excess of 12 months).
Sildenafil, however, can be taken as a regular daily prescription to provide background sexual stimulation. The newer agents avanafil, tadalafil and vardenafil are longer lasting and may be taken as a regular prescription on alternate days to provide background stimulation for erections. If these drugs are taken as a regular prescription, treatment should be continued for a minimum period of six weeks before their effectiveness can be adequately assessed.
| Parameter | Sildenafil | Tadalafil | Vardenafil |
|---|---|---|---|
| Parameter Time to maximum effect (hr) | Sildenafil 0.8 – 1 | Tadalafil 2 | Vardenafil 0.9 |
| Parameter Half-life (hr) | Sildenafil 2.6 – 3.7 | Tadalafil 17.5 | Vardenafil 3.9 |
Your consultant, GP or specialist nurse will advise you on the starting dose and will also monitor the effect to determine whether an increase in dosage is necessary.
When should they not be taken and what are the side effects?
These drugs should not be taken by patients currently receiving treatment for angina with organic nitrates (eg GTN, isosorbide or amyl nitrate). Interaction with these drugs can result in a dangerous fall in blood pressure. A similar fall in blood pressure may occur if the drugs are taken in association with alcohol and caution should be exercised under these circumstances.
Treatment should not be used in men for whom sexual activity is inadvisable, such as those with unstable angina or severe heart failure, and should not be used with any other forms of treatment for erectile dysfunction.
The drugs can be taken with food but the onset of activity may be delayed by a large meal, especially one containing exceptionally fatty foods.
The three most common side effects are headache (in 12%), flushing (in 10%) and indigestion (in 7%). Altered vision, usually a blue tinge, with dizziness, can occur in 3% and some patients experience aching in muscles. Higher doses are more likely to produce side effects, especially muscle pain. If dizziness occurs, it is advisable not to drive or to operate machinery.
Approximately 12% of men experience significant side effects overall, although only 3% need to stop the treatment as a result of these side effects.
| Side-effect | Sildenafil | Tadalafil | Vardenafil |
|---|---|---|---|
| Side-effect Headache | Sildenafil 12.8% | Tadalafil 14.5% | Vardenafil 16% |
| Side-effect Flushing | Sildenafil 10.4% | Tadalafil 4.1% | Vardenafil 12% |
| Side-effect Indigestion | Sildenafil 4.6% | Tadalafil 12.3% | Vardenafil 4% |
| Side-effect Nasal congestion | Sildenafil 1.1% | Tadalafil 4.3% | Vardenafil 10% |
| Side-effect Dizziness | Sildenafil 1.2% | Tadalafil 2.3% | Vardenafil 2% |
| Side-effect Abnormal vision | Sildenafil 1.9% | Tadalafil - | Vardenafil <2% |
| Side-effect Back pain | Sildenafil - | Tadalafil 6.55% | Vardenafil - |
| Side-effect Muscle aching | Sildenafil - | Tadalafil 5.7% | Vardenafil - |
There have been reports of sudden deaths in the USA, especially after the use of sildenafil. Some of these deaths have been linked to the use of organic nitrates but most have been attributed to the fact that physical exertion of any kind, including sexual activity, is associated with a degree of risk to the heart. Many of these deaths were due to unaccustomed exertion resulting in a heart attack or acute heart failure. If you are in any doubt about whether it is safe to take these drugs, consult your GP for further advice.
Other information
This leaflet contains guidelines and advice from professional bodies, together with information about the prescription of drugs. Treatment of patients will be planned with the consultant responsible for care, taking into account those drugs which are or are not available at the local hospital and what is appropriate for optimum patient care.
Who can I contact for more help or information?
We are smoke-free
Smoking is not allowed anywhere on the hospital campus. For advice and support in quitting, contact your GP or the free NHS stop smoking helpline on 0800 169 0 169.
Other formats
Help accessing this information in other formats is available. To find out more about the services we provide, please visit our patient information help page (see link below) or telephone 01223 256998. www.cuh.nhs.uk/contact-us/accessible-information/
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Cambridge University Hospitals
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Telephone +44 (0)1223 245151
https://www.cuh.nhs.uk/contact-us/contact-enquiries/