Viagra (sildenafil) UK based online prescription tablets

An introduction to Viagra, by Dr Nitin Shori

Viagra (sildenafil) is a medicine used to help treat erectile dysfunction in men over 18 years old. It's classed as a "PDE5 inhibitor" and was the first erectile dysfunction treatment to be launched in the UK by Pfizer. Viagra comes as a blue pill and is available in three strengths - 25mg, 50mg and 100mg, in pack sizes of four or eight tablets. The active ingredient of Viagra is also available as a generic medicine, called sildenafil. This generic form of Viagra contains the same active ingredient and is a fully licensed UK medicine, used in the same way.

How long does Viagra take to work?

Viagra should be taken at least 30 to 60 minutes before you wish to have sex. You will still need sexual stimulation to achieve an erection when you have taken Viagra.

How long does Viagra last?

Viagra remains effective for around four to five hours after you take it.

How does Viagra work?

An erection occurs when the penis fills with blood. The blood vessels that bring blood to the penis dilate, increasing the blood supply. Blood accumulates in the penis, causing an erection. Taking Viagra tablets allows better blood flow to the penis by relaxing the blood vessels.

The science behind Viagra

During arousal, the body releases a chemical known as 'cGMP nucleotide'. It plays an important part in achieving an erection as the cGMP nucleotide causes the muscles in the walls of the penis to relax which allows more blood to flow. Men who are suffering with impotence have an imbalance between the cGMP nucleotide and the PDE-5 enzyme. This imbalance makes erections more difficult to achieve and maintain. Sildenafil is the active ingredient of Viagra. It works by inhibiting the effects of the PDE-5 enzyme which breaks down the cGMP nucleotide. With the PDE-5 enzyme inhibited, impotent men should be able to achieve and enjoy longer lasting erections.

Who is Viagra for?

Viagra (active ingredient sildenafil) is for men over the age of 18 who are experiencing erectile dysfunction.

Who should not take Viagra?

Do not take Viagra if you are allergic to sildenafil or any of the other ingredients of the tablet. Viagra is not suitable for use by those with serious heart or liver problems, those who have had recently had a stroke or a heart attack, those with low blood pressure, or those with some rare inherited eye diseases. Viagra is also not suitable for women, or men under 18.

How do I take Viagra?

Viagra should be swallowed with a glass of water. It's best to take Viagra on an empty stomach.

Can I take Viagra with other medication?

You must let your doctor know if you are taking any other medications, whether prescribed or purchased over the counter, especially if you take nitrates for chest pain, riociguat for pulmonary hypertension or any recreational drugs called 'poppers'. Some herbal remedies and supplements may interfere with Viagra. It is also important to let us know if you use, or have used, other erectile dysfunction medications.

Viagra dosage

The usual starting dose of Viagra is 50mg, with the option to reduce to 25mg or increase to 100mg, depending on effectiveness and side effects experienced. Up to one dose can be taken in 24 hours.

Effectiveness of Viagra

Viagra contains the active ingredient sildenafil. It works by relaxing the blood vessels to the penis, allowing better blood flow when sexually aroused. Viagra is effective for most men with erectile dysfunction.

Side effects of Viagra

As with all medicines, Viagra can cause side effects, but not everyone experiences them. If taken at the recommended dosage, the side effects of this drug are usually mild and will pass with time. The most common side effects are headaches and facial flushing. Less common effects include indigestion, dizziness, stuffy nose and visual effects (a blue coloured tinge to vision, increased brightness of light or blurring). If you experience any troublesome side effects, or a prolonged and painful erection, stop using the medicine and seek medical assistance immediately.

Nitrates and alpha blockers

You shouldn't take Viagra with medications known as nitrates. Both of these cause the muscles that control the size of blood vessels to relax, which could cause a drastic drop in blood pressure. Nitrates are found in drugs used to treat chest pain and angina, and in the recreational drugs (e.g. poppers). It is advised not to combine medicines called `alpha blockers' with Viagra without speaking to a doctor, as this can also lower your blood pressure too much. Always consult your doctor before combining medicines and make sure you tell our online doctors about any other medicines you take. Always read the leaflet carefully before taking any medicine.

If Viagra does not work for you, there are alternative medications available. You could try Cialis (tadalafil), Levitra (vardenafil) or Spedra (avanafil). Cialis is effective for up to 36 hours, and can be taken as a once daily tablet (2.5mg or 5mg), or just when required (10mg or 20mg). Levitra comes in strengths of 5mg, 10mg and 20mg. It has been shown to be effective in a wide range of age groups and for men with conditions such as high blood pressure, diabetes, depression and high cholesterol. Spedra comes in strengths of 50mg, 100mg and 200mg, and has been shown to work well for men with erectile dysfunction caused by type 1 and type 2 diabetes. Spedra can work within 15-30 minutes of taking the dose - this is faster than Viagra, Levitra or Cialis.