Sildenafil and tadalafil are the two most widely prescribed medicines for erectile dysfunction (ED). Both belong to the same drug class and work in a similar way, yet they feel quite different in everyday use. One acts for a few hours, the other for up to a day and a half. This guide compares sildenafil vs tadalafil side by side so you can have a better-informed conversation with your doctor about which one suits your lifestyle.
How Sildenafil and Tadalafil Work
Both medicines are PDE5 inhibitors. During sexual arousal, the body releases nitric oxide, which relaxes the smooth muscle in the penis and lets more blood flow in. An enzyme called phosphodiesterase type 5 (PDE5) normally switches this process off. By blocking PDE5, sildenafil and tadalafil help the body maintain the blood flow needed for an erection.
An important point that many men do not realise: neither medicine causes an erection on its own. Sexual stimulation is still needed. They make a natural response easier, rather than creating one.
Sildenafil vs Tadalafil at a Glance
| Sildenafil | Tadalafil | |
|---|---|---|
| Original brand | Viagra | Cialis |
| Starts working | About 30–60 minutes | About 30 minutes to 2 hours |
| How long it works | Around 4–6 hours | Up to 36 hours |
| Effect of food | A heavy, high-fat meal can delay it | Not significantly affected by food |
| Common strengths | 25 mg, 50 mg, 100 mg | 2.5 mg and 5 mg (daily); 10 mg and 20 mg (as needed) |
| Daily dosing option | No | Yes, low-dose daily tablets |
| Other approved uses | Pulmonary arterial hypertension (different dosing) | Enlarged prostate (BPH) symptoms, pulmonary arterial hypertension |
Sildenafil: Fast-Acting and Predictable
Sildenafil was the first PDE5 inhibitor and has more than 25 years of real-world use behind it. It is usually taken about an hour before sexual activity, and its effect lasts for several hours. Many men like that it has a clear, predictable window.
The main practical drawback is that a large or fatty meal can slow its absorption, so it tends to work best on a light stomach. Doctors commonly start at 50 mg and adjust up or down depending on response and side effects. The maximum is one dose in 24 hours.
Popular generic sildenafil brands include Fildena 100 mg, Cenforce 100 mg and Aurogra 100 mg. You can see all strengths in our sildenafil range.
Tadalafil: Long-Lasting and Flexible
Tadalafil’s biggest advantage is its long duration. A single as-needed dose can remain effective for up to 36 hours, which is why it earned the nickname “the weekend pill”. This removes much of the pressure of timing, and food has little effect on how well it works.
Tadalafil is also available as a low daily dose (2.5 mg or 5 mg) taken at the same time every day. This keeps a steady level in the body, so there is no need to plan around a tablet at all. The daily 5 mg dose is also used to relieve urinary symptoms caused by an enlarged prostate. This makes it a practical option for men who have both conditions.
Common generic tadalafil options include Vidalista 20 mg and Tadarise 20 mg for as-needed use, and Vidalista 5 mg for daily use. Browse our full tadalafil range.
What About Vardenafil and Avanafil?
Two other PDE5 inhibitors are also available:
- Vardenafil works much like sildenafil, lasting around 4–5 hours. Some men who don’t respond well to one medicine find another suits them better.
- Avanafil is the newest of the group and can start working in as little as 15–30 minutes, with fewer reported visual side effects.
Side Effects to Know About
Because both medicines widen blood vessels, they share similar common side effects. These are usually mild and short-lived:
- Headache
- Facial flushing
- Blocked or runny nose
- Indigestion or heartburn
- Dizziness
There are a few differences. Sildenafil is more likely to cause temporary visual changes, such as a blue tint or sensitivity to light. Tadalafil is more likely to cause back pain or muscle aches, which typically appear 12–24 hours after a dose.
Seek urgent medical help if you have an erection lasting more than 4 hours (priapism), sudden loss of vision or hearing, or chest pain during sexual activity.
Who Should Not Take Them
PDE5 inhibitors are not safe for everyone. Do not take sildenafil or tadalafil if you:
- Use nitrate medicines for chest pain (such as nitroglycerin/GTN spray or isosorbide) or recreational “poppers”. The combination can cause a dangerous drop in blood pressure.
- Take riociguat for pulmonary hypertension.
- Have been advised by a doctor to avoid sexual activity because of a heart condition.
- Have had a recent heart attack or stroke, or have very low blood pressure.
Extra caution is needed if you take alpha-blockers for blood pressure or prostate problems, certain antifungals or HIV medicines, or if you have liver or kidney disease. Never take two different ED medicines together. Limit alcohol, which can reduce effectiveness and increase dizziness. Grapefruit juice can raise drug levels in the blood.
Which One Should You Choose?
There is no single “best” ED medicine. Large studies show sildenafil and tadalafil are similarly effective, so the right choice mostly comes down to your routine and preferences:
- Choose sildenafil if you prefer a shorter-acting tablet taken shortly before planned activity, or you have used it successfully before.
- Choose tadalafil if you want more spontaneity, a longer window of effect, or also have enlarged-prostate symptoms.
- Consider daily tadalafil if you are sexually active several times a week and would rather not plan around a tablet.
Your doctor will consider your heart health, other medicines and any side effects you’ve had before recommending a medicine and dose.
Frequently Asked Questions
Can I take sildenafil and tadalafil together?
No. Combining PDE5 inhibitors increases the risk of low blood pressure and other side effects without improving results.
Is tadalafil stronger than sildenafil?
Not exactly. They are similarly effective at their recommended doses. Tadalafil simply lasts longer, which some men experience as “stronger”.
Do I need to take them every day?
Sildenafil and as-needed tadalafil (10–20 mg) are taken only before sexual activity. Low-dose tadalafil (2.5–5 mg) is the option designed for daily use.
Does ED always need medication?
Not always. ED can be an early sign of heart disease, diabetes or high blood pressure, and lifestyle changes such as exercise, weight loss, stopping smoking and drinking less can make a real difference. Read our guide to tips for managing erectile dysfunction for more.
This article is for general information only and is not a substitute for professional medical advice. Always speak to a doctor or pharmacist before starting, stopping or changing any medicine.
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