The four PDE5 inhibitors approved in the United States, as one table taken from their prescribing information: usual doses, time to onset, half-life and the useful window that follows from it. The point the table makes is the one the article: Viagra, Cialis and the Rest: You Are Choosing a Duration, Not a Strength makes: you are choosing a duration, not a strength.
0.03 points
difference between tadalafil and sildenafil on a 30-point erectile function scale (95% CI −0.32 to 0.39) across 16 randomised trials in 5,189 men. What differs is half-life: 2.6–3.7 h for sildenafil, 17.5 h for tadalafil.
| Most common tadalafil complaint | Muscle ache and back pain |
|---|---|
| Most common sildenafil complaint | Facial flushing |
| Men reporting failure who were taking it incorrectly | Between 56% and 81% |
| Absolute contraindication | Nitrates, nitric oxide donors, amyl nitrite, nicorandil |
| Formats | CSV, JSON |
| License | CC BY 4.0, attribute Big Dick Pills |
| Checked | 24 September 2026 |
The four drugs, side by side
| Drug | Usual doses | Onset | Half-life | Useful window |
|---|---|---|---|---|
| Sildenafil (Viagra) | 25 to 100 mg | 30 to 60 min | 2.6 to 3.7 h | Up to 12 h |
| Tadalafil (Cialis) | 5 to 20 mg on demand; 2.5 to 5 mg daily | About 30 min, peak near 2 h | 17.5 h | Up to 36 h |
| Vardenafil (Levitra) | 5 to 20 mg | About 30 min | 3.9 h | Similar to sildenafil |
| Avanafil (Stendra) | 50 to 200 mg | 15 to 30 min | 6 to 17 h | Shorter than tadalafil |
How we built this
Doses, onset and half-life are taken from each product’s FDA prescribing information; the useful window is the label’s own guidance on timing. The head-to-head result is from the Chen et al. systematic review and meta-analysis of tadalafil versus sildenafil. The AUA and EAU guidelines, which recommend the class without ranking the drugs, are linked below.
What this cannot tell you
Which one suits you: that depends on your other medicines (nitrates are an absolute contraindication for all four), your kidneys and liver, and which side effect you would rather have. Not medical advice.
Use this data
The facts in this table (what a guideline says, what a label says, what a trial found) are not ours to own; repeat them anywhere. Our wording, table and layout are free to reuse, including commercially, under CC BY 4.0. Credit Big Dick Pills and link back; that is all we ask.
Sources
- Burnett AL, et al. Erectile Dysfunction: AUA Guideline. American Urological Association. AUA
- EAU Guidelines on Sexual and Reproductive Health: Management of Erectile Dysfunction. European Association of Urology. Uroweb
- Chen L, et al. Direct comparison of tadalafil with sildenafil for the treatment of erectile dysfunction: a systematic review and meta-analysis. International Urology and Nephrology, 2017. PubMed
- STENDRA (avanafil) prescribing information. US Food and Drug Administration. FDA