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Are sildenafil (Viagra) and tadalafil (Cialis) safe to use?

Any erectile dysfunction (ED) treatments that are available at a pharmacy or prescribed by your GP are generally safe for most people. However, like with most medications, there are some risks depending on other health issues you may have.  

The ED treatment products available at Well Pharmacy contain the active ingredients tadalafil or sildenafil. It is important that you don’t take ED medications if you [1,2]: 

  • have had an allergic reaction to tadalafil, sildenafil (Viagra), or any other medicines in the past 

  • are taking medicines called nitrates for chest pain 

  • have a serious heart condition 

  • Have a serious liver condition  

  • have recently had a stroke or a heart attack 

  • have low blood pressure or uncontrolled high blood pressure 

  • have ever lost your vision due to reduced blood flow to the eye 

As with any medication, there are potential side effects that you may experience when taking ED medications, such as [1,2]: 

  • headaches 

  • feeling sick 

  • hot flushes, including facial flushing 

  • indigestion 

  • a colour tinge to your vision or blurred vision 

  • stuffy nose 

  • dizziness 

If you get these side effects, you can keep taking the medicine, but it’s important that you tell a doctor or pharmacist if they bother you or do not go away. 

Serious side effects 

Serious side effects when taking ED medications are rare. If you experience any of the below side effects, stop taking the medication immediately and contact your GP [1,2]. 

  • Chest pains - if this happens during or after sex, sit up gently and try to relax. Don’t use nitrates to treat your chest pain. 

  • Prolonged and sometimes painful erections - if you have an erection that lasts for more than 4 hours, contact your GP.  

  • A sudden decrease or loss of vision. 

  • A serious skin reaction - symptoms may include fever (a high temperature), severe peeling and swelling of the skin, blistering of the mouth, genitals, and around the eyes. 

  • Seizures. 


Here are some of our most frequently asked questions around treatments for erectile dysfunction.


February 2022

Next review

February 2024

Reviewed by

Gill Stone MRPharmS

Further reading on erectile dysfunction

Sildenafil Vs tadalafil

Sildenafil and tadalafil are medicines used to treat erection problems, more commonly known as erectile dysfunction (ED). Find out how they differ here.

What erectile dysfunction treatments are there?

Find out about some of the common erectile dysfunction treatment options to see what might work best for you.

What causes erectile dysfunction?

Erectile dysfunction can have many causes. Learn more about some of the common causes of erectile dysfunction. Well Pharmacy is here to support you.


  1. 1.

    Tadalafil: a medicine to treat erection problems and symptoms of an enlarged prostate. Published September 10, 2019. Accessed December 21, 2021.
  2. 2.

    Sildenafil (Viagra): medicine for erection problems. Published August 29, 2018. Accessed December 21, 2021.
  3. 3.

    Tadalafil 10 mg film-coated tablets - Summary of Product Characteristics (SmPC) - (emc). Accessed December 21, 2021.
  4. 4.

    Sildenafil 50 mg film-coated tablets - Patient Information Leaflet (PIL) - (emc). Accessed December 29, 2021.