Generic sildenafil and Viagra contain the same active ingredient. Viagra is the branded version. The manufacturer, tablet appearance and inactive ingredients may differ, but UK-licensed products must meet the required standards for quality, safety and effectiveness.

Sildenafil is available in 25mg, 50mg and 100mg strengths. The appropriate strength depends on your health, current medicines and response to previous treatment. The usual starting dose for many men is 50mg, but the prescriber may recommend a different strength.

Take the prescribed tablet approximately one hour before sexual activity and swallow it whole with water. Do not take more than one dose within 24 hours.

Sildenafil usually starts working within 30 to 60 minutes, although this can vary. Taking it after a large or high-fat meal may delay its effect.

Sildenafil can remain effective for approximately four hours. This does not mean you will have a continuous erection. Sexual stimulation is still required for an erection to occur.

No. Sildenafil does not increase libido or sexual desire. It supports the physical erectile response when you are sexually stimulated.

Sildenafil can be taken with or without food. However, a large or high-fat meal may delay how quickly it begins working.

Drinking excessive alcohol can make it more difficult to achieve an erection and may increase side effects such as dizziness or low blood pressure. Keep alcohol intake low when using sildenafil.

No. Do not take sildenafil with nitrate medicines used for chest pain or with recreational drugs known as poppers. The combination can cause a dangerous fall in blood pressure.

Do not combine sildenafil with Viagra, tadalafil, Cialis or another erectile-dysfunction treatment unless a clinician has specifically instructed you to do so.

Common side effects may include headache, flushing, indigestion, nausea, nasal congestion, dizziness and temporary changes in vision. Speak to a healthcare professional if a side effect concerns you or does not improve.

Do not take an additional dose or exceed the prescribed strength. Sildenafil may be less effective after a heavy meal, excessive alcohol or without sufficient sexual stimulation. Speak to your prescriber if it repeatedly does not work.

Seek urgent medical help if you experience chest pain, a painful or prolonged erection lasting more than four hours, sudden vision or hearing loss, difficulty breathing or swelling of the face, lips, tongue or throat.

The manufacturer, packaging, tablet colour and appearance may vary depending on availability. You will receive a UK-licensed generic sildenafil product in the strength approved by the prescriber.

Yes. This product is supplied following a confidential online clinical assessment. A prescriber will review your answers and determine whether sildenafil and the selected strength are suitable for you.

Yes. This product is supplied following a confidential online clinical assessment. A prescriber will review your answers and determine whether sildenafil and the selected strength are suitable for you.