Viagra (sildenafil citrate) is a prescription-only medicine that is used to treat men with erectile dysfunction (ED).
Erectile dysfunction is a medical condition. So your doctor should be the first port of call for any questions you may have.
You can only get genuine Viagra by prescription through legitimate channels. Any other way means you may be putting your health at risk.
Pfizer is the maker of Viagra and has been providing medications for people in the United Kingdom for over 50 years.