What are the side effects of viagra (sildenafil)?

Many: Common side effects of viagra (sildenafil) include headache, flushing, heartburn, nasal congestion uterine contractions (period cramps), abnormal vision, diarrhea, dizziness, rash, high or low sugar levels, high uric acid levels, high sodium blood level, abnormal liver function tests , and photosensitivity. Serious reactions can include heart attack, stroke, sudden death, prolonged painful erection.

See below: Viagra is generally both very safe and well tolerated. Most common side effects: headache; flushing; upset stomach; changes in color vision (blue tinge); stuffy/runny nose; and back or muscle pain all of which are generally mild and improve with repeated use or dose reduction. Erection lasting >4hrs or sudden hearing or vision loss very rare. Cannot use with nitrates or “severe” heart disease.