Sildenafil or tadalafil: what’s the difference?

Sildenafil and tadalafil treat erectile dysfunction in a similar way. They relax blood vessels and make it easier for blood to reach the penis when you are sexually aroused. They do not create desire and they do not cause an automatic or continuous erection.

The practical difference is the treatment window. Sildenafil is commonly taken before sex and has a shorter duration. Tadalafil can be taken when needed and may remain effective for up to 36 hours; some people may instead be prescribed a lower daily dose. A longer window does not mean a 36-hour erection — it means the medicine may help when sexual stimulation happens during that time.

The safest option depends on your heart health, blood pressure, other medicines and the pattern of your symptoms. Nitrates such as glyceryl trinitrate (GTN), and recreational nitrites known as poppers, can combine with these medicines to cause a dangerous fall in blood pressure. You should also disclose alpha-blockers, blood-pressure medicines and any recent heart or circulation problem.

Erection problems can sometimes be linked with diabetes, cardiovascular disease, medicines, stress or relationship factors. That is why a useful assessment asks about more than the erection itself.

• Choose a regulated service and answer every safety question honestly.
• Follow the prescribed dose; do not combine erectile-dysfunction medicines.
• Seek urgent help for chest pain, sudden sight loss or an erection lasting longer than four hours.

One unsuccessful attempt does not always mean the medicine is unsuitable. Timing, a heavy meal, alcohol, anxiety and insufficient stimulation can all affect the result. Do not increase the dose yourself. Read the patient leaflet and ask the prescriber how to use the medicine correctly.

If erection problems keep happening, arrange a health review rather than repeatedly changing medicines. Blood pressure, blood glucose, cholesterol and sometimes hormones may need checking, depending on your history.