By the Medsmingle Team · Updated 13 November 2026
This is a prescription medicine. Only take it if it has been prescribed for you after a medical assessment, and follow your doctor’s and pharmacist’s instructions.
Sildenafil and tadalafil are the two most prescribed medicines for erectile dysfunction. Both are PDE5 inhibitors, but response and tolerability vary. The main differences are timing, flexibility and side effects.
At a glance
| Sildenafil (Viagra) | Tadalafil (Cialis) | |
|---|---|---|
| Starts working | 30–60 minutes | 30 minutes–2 hours |
| Lasts | About 4–6 hours | Up to 36 hours |
| Effect of a heavy meal | Can delay it | Little effect |
| Daily low-dose option | No | Yes (2.5–5 mg) |
| Also treats BPH | No | Yes (5 mg daily) |
| Typical starting dose (as needed) | 50 mg | 10 mg |
| More common side effects | Headache, flushing, vision tinge | Headache, back and muscle pain |
Which suits whom?
Sildenafil may suit men who have sex less often, prefer a shorter-acting medicine, or prefer as-needed treatment.
Tadalafil may suit men who want more spontaneity, are sexually active several times a week (daily dosing), or also have urinary symptoms from an enlarged prostate.
Neither is “stronger” overall. If one doesn’t suit you after reviewing the prescribed dose and correct use, your doctor may suggest switching.
Important safety points for both
- Never take either with nitrates, “poppers” or riociguat
- Get emergency help for chest pain, an erection lasting over 4 hours, or sudden vision or hearing loss
- Do not combine them or switch without a prescriber’s plan; tadalafil can remain active beyond the day it is taken
- Tell your doctor about all medicines, especially alpha-blockers, antifungals, HIV medicines and some antibiotics
Read the full guides: sildenafil and tadalafil.
Frequently asked questions
Can I switch from sildenafil to tadalafil?
Only with a prescriber’s advice. The waiting period depends on the medicines, doses, interactions and your kidney or liver function; there is no switching rule suitable for everyone.
Which has fewer side effects?
They’re similar overall. Sildenafil more often causes flushing and vision tinge; tadalafil more often causes back pain.
For questions about a prescription or symptoms, speak with your own doctor or pharmacist. For website enquiries, contact our team.
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General information only. It isn’t a substitute for advice from your doctor or pharmacist.
Sources
MedlinePlus: sildenafil and tadalafil.
