Sildenafil, Tadalafil, Vardenafil and Avanafil: A Plain-Language Comparison
Short answer: sildenafil, tadalafil, vardenafil and avanafil all belong to the same family of medicines (PDE5 inhibitors) and work in the same basic way. They differ mainly in how quickly they start, how long they last, how food affects them and which side effects are more common. Doctors choose between them based on your health, other medicines and what you want from treatment.
How all four work
During sexual arousal the body releases nitric oxide, which raises a messenger molecule called cGMP in the penile blood vessels. cGMP relaxes muscle in the artery walls and lets blood flow in, producing an erection. The enzyme PDE5 breaks cGMP down. All four medicines block PDE5, so the arousal signal lasts longer and works better.
Because the mechanism is shared, the key rules are shared too: they work only with sexual stimulation, they do not increase desire, they are not for use with nitrate medicines, and they should be used no more than once in 24 hours unless a doctor says otherwise. For the shared safety rules, read our guide to ED pills and nitrates.
At a glance: key differences
| Feature | Sildenafil | Tadalafil | Vardenafil | Avanafil |
|---|---|---|---|---|
| Typical onset | 30 to 60 minutes | About 30 minutes or more | 25 to 60 minutes | As early as 15 to 30 minutes |
| Typical duration | About 4 hours | Up to 36 hours | About 4 to 5 hours | Several hours; around 6 hours in studies |
| Usual strengths | 25, 50, 100 mg | 2.5 to 20 mg (daily and on-demand) | 5, 10, 20 mg | 50, 100, 200 mg |
| Effect of a heavy meal | Can delay onset | Not significant | High-fat meal can delay onset | Less affected than sildenafil |
| Daily low-dose option | No | Yes | No | No |
| Half-life (approx.) | 4 hours | 17 hours | 4 to 5 hours | About 5 hours |
These figures are typical values from product information and trials. Individual results vary.
Sildenafil
Sildenafil was the first widely used ED tablet and has the longest track record. It is usually taken about an hour before sex, and its effect lasts around four hours. A heavy or fatty meal can delay absorption. Common side effects include headache, flushing, indigestion and a blocked nose, and some men notice a bluish tint to their vision. Our article on how long sildenafil takes to work covers timing in detail, and you can see product labels in our sildenafil category.
Tadalafil
Tadalafil is known for its long window of effect, which can reach up to 36 hours. It is also the only one routinely offered as a low daily dose, which can suit men who want spontaneity or who also have urinary symptoms from an enlarged prostate. Meals do not significantly change how it works. Back pain and muscle aches are more typical side effects than with the others. Our article on daily vs on-demand tadalafil explains the two approaches, and the tadalafil category lists product information.
Vardenafil
Vardenafil acts in a similar way and over a similar time span to sildenafil, usually taking effect in 25 to 60 minutes and lasting four to five hours. A high-fat meal can delay it, and it is also available in dissolving tablet forms in some countries. It can affect heart rhythm in a small number of people, so it needs particular caution for men with certain heart rhythm conditions or those taking some heart rhythm medicines. See our vardenafil category for labels.
Avanafil
Avanafil is the newest of the four. It is absorbed quickly, and some men notice an effect within 15 to 30 minutes. It is less affected by food than sildenafil, and studies suggest relatively few visual side effects. Common side effects include headache, flushing, nasal congestion and back pain. Because it is newer and available in fewer countries, there is less long-term experience than with sildenafil or tadalafil. Our avanafil category lists product details.
How doctors choose between them
- How often you have sex. Occasional or planned sex may suit a short-acting option. Frequent sex or a wish for spontaneity may suit tadalafil.
- Food and routine. If you often eat a large dinner before intimacy, tadalafil or avanafil may be less affected than sildenafil or vardenafil.
- Other conditions. Prostate symptoms, heart rhythm problems, eye disease, liver or kidney impairment and blood pressure all influence the choice.
- Other medicines. Alpha-blockers, blood pressure medicines, some antifungals, antibiotics and HIV drugs can interact, and nitrates are never combined with these tablets.
- Side effect history. If one drug causes troublesome back pain or visual changes, another may be better tolerated.
- Cost and availability. Generic versions of the first three are widely available in many countries.
Switching between these medicines is common and not a sign of failure. If one does not work after several properly timed attempts, a clinician can adjust dose or try another option, rather than you taking extra tablets.
What none of them can do
- They do not cure the underlying cause of erectile dysfunction.
- They do not raise testosterone or sexual desire.
- They do not work without arousal.
- They do not protect against sexually transmitted infections or prevent pregnancy.
If erections have changed, it is worth looking for causes such as blood pressure, diabetes, heart disease, sleep problems, hormones, stress or medicines. Our articles on common causes of erectile dysfunction, blood pressure and erections and sleep, erections and testosterone explore these links.
Safety points that apply to all four
- Never use with nitrates (for chest pain), and avoid riociguat.
- Tell your doctor about all medicines, including alpha-blockers and other blood pressure drugs.
- Seek urgent help for an erection lasting longer than four hours, sudden loss of vision or hearing, chest pain or fainting.
- Have heart disease, a recent stroke or heart attack, or severe liver or kidney problems assessed before use.
- Obtain medicines only from legitimate, regulated sources; counterfeit tablets are a real risk.
- Store them as described in our guide to storing medicines safely at home, away from children.
Beyond tablets
Tablets are only one part of treatment. Lifestyle changes, counselling for anxiety, treating underlying conditions and, where appropriate, other medical treatments can all play a role. Our overview of the best medicines and treatments for erectile dysfunction describes the options, and our complete guide to erectile dysfunction is a good starting point for a wider picture. If PE is the main concern rather than ED, see our article on dapoxetine for premature ejaculation.
If you are unsure whether to see a doctor, read when to see a doctor for erectile dysfunction. You can also read our drug policy and FAQs to see how we handle medicine information.
Frequently asked questions
Which ED tablet is the strongest?
“Strongest” is not a helpful measure. All four are effective for many men, and the best choice depends on onset, duration, side effects and your health.
Which works fastest?
Avanafil is often reported to start working soonest, sometimes within 15 to 30 minutes, but individual response varies.
Which lasts longest?
Tadalafil, with an effect window of up to 36 hours.
Can I take two different ED tablets together?
No. Combining PDE5 inhibitors increases side effects and risk without a proven benefit.
Are generics as good as brand names?
Generic versions of regulated medicines contain the same active ingredient at the same strength. Make sure the product comes from a regulated source.
Can I switch if my first tablet does not work?
Yes, but speak to a doctor or pharmacist first so that dose, timing and safety checks are right for the new medicine.
Conclusion
Sildenafil, tadalafil, vardenafil and avanafil share one mechanism but differ in speed, duration, food effects and side effects. Tadalafil stands out for its long window and daily option, avanafil for quick onset, and sildenafil for the largest body of experience. A doctor or pharmacist can help you pick the one that fits your health and lifestyle, and check that it is safe alongside your other medicines.
References
- U.S. FDA prescribing information for Viagra, Cialis, Levitra and Stendra.
- NHS medicine information for sildenafil, tadalafil, vardenafil and avanafil.
- European Association of Urology guidelines on sexual and reproductive health.
This article is general education, not individual medical advice. It has not been written as a substitute for a consultation with a licensed healthcare professional.
