You should avoid Viagra and contact your doctor if you:
Are allergic to sildenafil or any ingredient in the product.
Take nitrates (medicines for chest pain/angina) or guanylate cyclase stimulators like riociguat – can cause dangerously low blood pressure.
Have severe heart problems, recent heart attack, or stroke (discuss with your doctor).
Experience an erection lasting more than 4 hours (priapism) — this is a medical emergency and can cause permanent damage.
Experience sudden vision loss in one or both eyes – stop using immediately and seek medical help.
VIAGRA can cause serious side effects. Rarely reported side effects include:
an erection that will not go away (priapism).
If you have an erection that lasts more than 4 hours, get medical help right away.
If it is not treated right away, priapism can permanently damage your penis.
sudden vision loss in one or both eyes.
Sudden vision loss can be a sign of a serious eye problem called non-arteritic anterior ischemic optic neuropathy (NAION).
Stop taking VIAGRA and call your healthcare provider right away if you have any sudden vision loss.
sudden hearing decrease or hearing loss.
Some people may also have ringing in their ears (tinnitus) or dizziness.
If you have these symptoms, stop taking VIAGRA and contact a doctor right away.
Things to Know Before Use
Viagra does not protect against STDs or HIV.
It should only be used under medical supervision and typically once per day.
It may interact with other medicines – especially nitrates, blood pressure medicines, and certain antifungals/antibiotics – so tell your doctor all medicines you take.