Key facts
- Both are PDE5 inhibitors and need sexual arousal to work.
- Tadalafil's effect can last up to 36 hours.
- Tadalafil can also be taken as a daily lower-dose tablet.
- Neither is usually prescribed with nitrates.
General information only, not a recommendation. Your prescriber chooses the medicine and strength.
| Sildenafil | Tadalafil | |
|---|---|---|
| Brand example | Viagra | Cialis |
| How it's taken | About an hour before sex, when needed | Before sex when needed, or a daily tablet |
| How long it can last | Ask your prescriber (see leaflet) | Up to 36 hours |
| Maximum | Not more than 1 tablet a day | As prescribed |
| Common side effects | Headache, dizziness, stuffy nose, upset stomach, temporary vision changes | Indigestion, muscle aches, back pain, headache, stuffy nose |
| Grapefruit | Avoid | Avoid |
| Nitrates | Not usually prescribed together | Not usually prescribed together |
See sildenafil explained and tadalafil explained.