If you experience any of the following serious side effects, stop taking Viagra and seek emergency medical attention or notify your doctor immediately:

• an allergic reaction (difficulty breathing; closing of the throat; swelling of the lips, tongue, or face; or hives);
• chest pain or an irregular heartbeat;
• swelling of the ankles or legs;
• shortness of breath;
• prolonged or severe dizziness;
• a prolonged (lasting longer than 4 hours) or painful erection;
• dizziness, nausea, or angina (pain, tightness, discomfort, numbness, or tingling in the chest, arms, neck, or jaw).

Other, less serious side effects may be more likely to occur. Continue to take Viagra and talk to your doctor if you experience

• flushing;
• mild dizziness;
• headache;
• nasal congestion;
• diarrhea;
• temporary blue tint in vision or other vision abnormalities;
• itching or a rash.

Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome.