Sildenafil vs. Tadalafil
Viagra vs. Cialis — the two most widely prescribed erectile dysfunction medications compared on onset, duration, dosing flexibility, side effects, and lifestyle fit.
| Feature | Sildenafil (Viagra) | Tadalafil (Cialis) |
|---|---|---|
| Brand Name | Viagra | Cialis |
| Drug Class | PDE5 Inhibitor | PDE5 Inhibitor |
| Onset of Action | 30-60 minutes | 30 minutes to 2 hours |
| Duration of Effect | 4-6 hours | Up to 36 hours |
| Half-Life | 3-5 hours | 17.5 hours |
| As-Needed Dosing | 25 mg, 50 mg, 100 mg | 5 mg, 10 mg, 20 mg |
| Daily Dosing Option | No | Yes (2.5 mg or 5 mg daily) |
| Food Interaction | High-fat meals delay onset by ~1 hr | Not significantly affected by food |
| Also Treats BPH | No | Yes (5 mg daily) |
| Visual Side Effects | Yes — blue tint (PDE6 cross-reactivity) | Rare (higher PDE5/PDE6 selectivity) |
| Back Pain / Myalgia | Uncommon | Common (6%) — PDE11 effect |
| Headache Rate | 16% | 15% |
| Nitrate Washout | 24 hours | 48 hours (longer half-life) |
| Generic Available | Yes (since 2013) | Yes (since 2018) |
| First FDA Approval | March 1998 | November 2003 |
Key Differences
Duration of Action
The most significant difference. Sildenafil works for 4-6 hours, requiring timing around sexual activity. Tadalafil lasts up to 36 hours, allowing for more spontaneity — earning it the nickname “the weekend pill.”
Daily Dosing
Tadalafil is the only PDE5 inhibitor with an FDA-approved daily dosing option (2.5-5 mg). This provides continuous erectile readiness without planning. Sildenafil is taken only as needed.
Food Sensitivity
Sildenafil absorption is significantly delayed by high-fat meals. Tadalafil is not meaningfully affected by food, making it more convenient with meals or date nights.
Side Effect Profile
Sildenafil is more likely to cause visual disturbances (blue-tinted vision) due to PDE6 cross-reactivity. Tadalafil is more likely to cause back pain and myalgia due to PDE11 cross-reactivity.
BPH Treatment
Tadalafil 5 mg daily is FDA-approved for benign prostatic hyperplasia (BPH), making it a two-in-one solution for men with both ED and urinary symptoms. Sildenafil does not have this indication.
Nitrate Safety Window
Due to its longer half-life, tadalafil requires a 48-hour washout before nitrate use (vs. 24 hours for sildenafil). This is critical information for emergency cardiac care.
Which One Is Right for You?
Sildenafil may be better if you:
- Prefer a faster onset (30-60 min vs. up to 2 hrs)
- Want to use it only when needed (lower overall drug exposure)
- Are prone to back pain or muscle aches
- Need a shorter nitrate-safety washout window
Tadalafil may be better if you:
- Want spontaneity without timing a pill (36-hour window)
- Prefer daily dosing for continuous readiness
- Also have BPH / urinary symptoms
- Want to eat freely without worrying about food interactions
Talk to a doctor about ED treatment
Our physicians can help determine the right medication and dosing strategy for your needs.
Get startedThis comparison is for educational purposes only and is not medical advice. Both sildenafil and tadalafil are equally effective first-line treatments for erectile dysfunction. The best choice depends on your individual preferences, health profile, and other medications. Always consult your healthcare provider. Last reviewed: March 2026.