Key facts
- Usually taken about an hour before sex, and needs sexual arousal to work.
- Do not take more than 1 tablet a day.
- Not usually prescribed with nitrates or riociguat.
- Avoid grapefruit and grapefruit juice while taking it.
What it is
Sildenafil is a PDE5 inhibitor used to treat erection problems. Viagra is one brand. Generic versions contain the same active ingredient.
How it's taken
It's usually taken about an hour before sexual activity. How long it takes to work varies from person to person. Don't take more than 1 tablet a day. Your prescriber will tell you which strength to take.
Common side effects
Common side effects include headaches, dizziness, a stuffy nose, an upset stomach and temporary changes in vision, such as blurred vision. Tell your prescriber if they bother you or don't go away.
Things to avoid
- It's not usually prescribed together with nitrates (often used for chest pain) or riociguat.
- Don't eat grapefruit or drink grapefruit juice, as it can make side effects more likely.
- Drinking too much alcohol can make it harder to get an erection.
Get urgent help if
Call 999 or go to A&E if you have an erection lasting more than 3 to 4 hours, chest pain, or signs of a serious allergic reaction. See urgent warning signs.