Tadalafil vs Sildenafil: Which is better?

Dr Kathryn Basford

Medically reviewed by

Dr Kathryn Basford

Last reviewed: 10 Nov 2021

Tadalafil and sildenafil are both medicines you can use to help treat erectile dysfunction, but which is better? Choosing between tadalafil and sildenafil will depend on how often you need to use them. There are other factors to consider too, such as side effects or interactions with other medicines. You can try sildenafil or tadalafil on separate occasions and decide which one you prefer after your experiences with them.

Somebody sat down comparing two medications

What’s the difference between tadalafil and sildenafil?

The main differences between tadalafil and sildenafil are how quickly they work and how long they last. Tadalafil helps you get an erection within 30 minutes, whereas sildenafil can take up to an hour. Sildenafil can be effective for up to 4 hours. With tadalafil, the effects can last 24 to 36 hours, which is much longer than sildenafil.

Tadalafil is available in 4 strengths (2.5mg, 5mg, 10mg and 20mg) and sildenafil is available in 3 strengths (25mg, 50mg and 100mg). The lower dose strengths (2.5mg and 5mg) of tadalafil are used daily for men who have sex more than 2 times a week. The higher doses of tadalafil and the sildenafil doses are for use as needed, not more than once a day.

Tadalafil and sildenafil are each made by different medicines companies as they are both generic or ‘off patent’. You may have heard of the brand name Viagra and its active ingredient is sildenafil. Tadalafil is also known by the brand name Cialis. Brand name medicines tend to be more expensive, so it’s cheaper to get either tadalafil or sildenafil as generic medicines. Generic medications work in the same way as brand name medications.

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Side effects

Side effects of tadalafil

When you take tadalafil you may start to get a headache or find that your face looks red. It’s also possible that your nose will feel blocked. There may be some changes to your blood pressure that make you feel dizzy or affect how well you can see, so you should not drive straight after taking a tadalafil tablet. If you take a small dose of tadalafil daily, you’re less likely to get these side effects.

Side effects of sildenafil

Sildenafil can make your body feel hot and like tadalafil, you may get a headache. You might get a stuffy nose or a bit of a stomach upset. Less common side effects of sildenafil include vomiting, dry mouth, a skin rash and bloodshot or red eyes. To prevent side effects, you may want to start with a small dose of sildenafil like 25mg or 50mg.

If you feel chest pain or have an erection that lasts longer than 4 hours after you take tadalafil or sildenafil, call 999 for emergency medical attention.


Your dosage of tadalafil will depend on the amount you need to take to get an erection and how often you want to have sex. You can take either a 2.5mg or 5mg tablet of tadalafil once a day if you want to have sex more than twice a week. You should take your 2.5mg or 5mg tablet every day and at the same time each day.

If you plan on having sex less often, you can take 1 tablet of either 10mg or 20mg tadalafil once or twice a week. You should take one at least 30 to 60 minutes before you have sex. The effects of tadalafil can last for up to 36 hours. You should not take more than 1 tadalafil tablet in 24 hours. If tadalafil is not right for you, sildenafil is a good alternative as its effects come on more gradually.

Similarly, you should only take 1 tablet of sildenafil in 24 hours, even if you take the lowest dose of 25mg. Your doctor may suggest you start with the 50mg dose of sildenafil. If 50mg is too much for you, your doctor may recommend you take the lower dose of 25mg sildenafil.

You may need to take a higher dose of 100mg sildenafil if the 50mg tablets do not work for you.

Interactions with other medicines

You might be taking other medicines that could interact with sildenafil or tadalafil. These other medicines can affect how tadalafil or sildenafil work. So it’s a good idea to speak to a doctor first before you take tadalafil or sildenafil.

You should not take tadalafil and sildenafil at the same time.


Before you take tadalafil, let your doctor know if you take other medicines like:

  • other erectile dysfunction treatments, including Viagra (sildenafil)
  • nitrates, such as isosorbide mononitrate for chest pain (angina)
  • tamsulosin or another benign prostatic hyperplasia (BPH) treatment
  • high blood pressure medicines
  • bosentan or riociguat
  • ritonavir for HIV treatment
  • phenytoin, phenobarbital or carbamazepine for epilepsy
  • antibiotics, such as erythromycin, clarithromycin, or rifampicin
  • antifungal medicines, such as ketoconazole or itraconazole
  • any over-the-counter products you have bought from a pharmacy


Sildenafil can interact with other medicines you take, like these:

  • other erectile dysfunction treatments, including Cialis (tadalafil)
  • nitrates for chest pain, such as or glyceryl trinitrate (GTN) or isosorbide mononitrate
  • protease inhibitors or other HIV treatments
  • alpha-blockers for high blood pressure (doxazosin or alfuzosin)
  • recreational drugs that affect your blood pressure, such as ‘poppers’
  • antibiotics (erythromycin)


Whether you take tadalafil or sildenafil, they’re both effective treatments for erectile dysfunction. Although they work in a similar way, the amount you need for them to work is different. Tadalafil and sildenafil can both cause headaches or make you feel dizzy as side effects. And if you take any other medicines, your doctor can help you choose between tadalafil and sildenafil.

Medically reviewed by:
Dr Kathryn Basford

Dr Kathryn Basford is a qualified GP who works as a GP in London, as well as with ZAVA. She graduated from the University of Manchester and completed her GP training through Whipps Cross Hospital in London.

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Article created: 10 Nov 2021

Last reviewed: 10 Nov 2021

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