Educational information only. This article has not yet been independently medically reviewed. It is not a diagnosis, a prescription, or a substitute for advice from a qualified healthcare professional.
What are sildenafil and Viagra?
Sildenafil is the active ingredient in Viagra. Viagra is a brand name; licensed generic sildenafil contains the same active medicine. Packaging and inactive ingredients may differ, but authorised generic medicines must meet regulatory standards for quality and equivalence. Neither the brand name nor the price makes a medicine suitable for everyone.
Sildenafil is commonly used to treat erectile dysfunction (ED): difficulty getting or keeping an erection firm enough for sexual activity. Sildenafil is also used for pulmonary arterial hypertension under different treatment arrangements. These uses have different prescribing requirements and should not be confused.
How does it work?
During sexual arousal, the body releases signals that relax blood vessels in the penis, allowing more blood to enter. Sildenafil blocks an enzyme called phosphodiesterase type 5 (PDE5), helping this normal response last long enough to support an erection.
Sexual stimulation is still needed. Sildenafil does not cause an automatic erection, and it is not an aphrodisiac. It does not directly increase testosterone, create sexual desire, enlarge the penis, or cure every cause of erectile difficulties.
For ED, it commonly starts working within 30 to 60 minutes. A heavy meal can delay its effect. It can help the erectile response for several hours, often around four hours, but this varies. That does not mean an erection should last for four hours. An erection should normally subside after sexual activity.
How can it affect men's health?
For someone with ED who can safely take it, sildenafil may improve the ability to achieve and maintain an erection. This can support sexual satisfaction and reduce some of the worry surrounding sexual activity. Results differ between people, and relationship concerns or performance anxiety may also need attention.
Sildenafil treats a symptom; it does not necessarily treat its underlying cause. Repeated erectile difficulties can be associated with diabetes, high blood pressure, cardiovascular disease, medication effects, stress, anxiety, or hormonal problems. They sometimes provide an early reason to check general health.
If difficulties keep happening, speak with a healthcare professional rather than simply increasing medicine use. A review may include blood pressure, blood sugar, cholesterol, current medicines, and emotional wellbeing. Exercise, stopping smoking, adequate sleep, and addressing harmful alcohol use can support overall and sexual health alongside appropriate treatment.
Common side effects
Possible side effects include:
- Headache and facial flushing.
- Indigestion or nausea.
- A blocked nose.
- Dizziness.
- Temporary visual changes, such as blurred vision or a colour tint.
Not everyone experiences these effects. If you feel dizzy or your vision is affected, do not drive or operate machinery. Discuss troublesome or persistent symptoms with a pharmacist or doctor.
Important interactions and who needs extra care
Sildenafil can lower blood pressure. Never combine it with nitrate medicines used for chest pain, such as glyceryl trinitrate (GTN) or isosorbide, or with recreational nitrites known as “poppers”. These combinations can cause a dangerous fall in blood pressure. It must also not be combined with riociguat.
Tell a healthcare professional about all medicines and supplements you take. Alpha blockers used for prostate symptoms or blood pressure, other blood-pressure medicines, and medicines that alter sildenafil breakdown can change the risk of side effects. Do not combine it with another ED medicine unless a specialist specifically directs you to do so.
A clinician needs to assess suitability if you have heart disease, very low blood pressure, a recent heart attack or stroke, serious liver or kidney problems, certain eye disorders, or a condition that increases the risk of a prolonged erection. Some of these conditions rule out use. If you have been advised to avoid sexual activity because of your heart health, do not use sildenafil without medical assessment.
Use only a regulated pharmacy or authorised healthcare service. Products from unverified websites may contain the wrong ingredient or dose. Follow the directions for the product prescribed or supplied to you; do not take extra doses to force a response.
When to get urgent help
- Chest pain during or after sex: stop sexual activity and seek emergency help. Do not take a nitrate medicine yourself. Tell emergency staff that you took sildenafil and when you took it.
- A prolonged or painful erection: seek urgent medical help immediately; do not wait for it to reach four hours. An erection lasting four hours or longer is a medical emergency because it can damage penile tissue.
- Sudden loss of vision or sudden hearing loss: stop taking sildenafil and get urgent medical help.
- Trouble breathing or swelling of the lips, tongue, or throat: call emergency services immediately because these may indicate a severe allergic reaction.
Does Viagra protect against pregnancy or infections?
No. Sildenafil is not contraception and does not protect against sexually transmitted infections. Safer-sex precautions are still needed. It is also not a standard treatment for premature ejaculation or a general “men's energy” supplement.
The bottom line
Viagra and sildenafil are not two different active medicines: Viagra contains sildenafil. For appropriately assessed men with ED, it can help the natural erectile response. Its benefits must be balanced against side effects, health conditions, and medicine interactions. Persistent erectile difficulties deserve a health assessment, not just a performance-focused solution.