Get emergency medical help if you have signs of an allergic reaction to sildenafil: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.
Stop taking sildenafil and get emergency medical help if you have:
heart attack symptoms - chest pain or pressure, pain spreading to your jaw or shoulder, nausea, sweating;
vision changes or sudden vision loss;
erection is painful or lasts longer than 4 hours (prolonged erection can damage the penis);
ringing in your ears, or sudden hearing loss;
irregular heartbeat;
swelling in your hands, ankles, or feet;
shortness of breath;
seizure (convulsions); or
a light-headed feeling, like you might pass out.
Common sildenafil side effects may include:
flushing (warmth, redness, or tingly feeling);
headache, dizziness;
heartburn, nausea, or upset stomach
abnormal vision (blurred vision, changes in color vision)
runny or stuffy nose, nosebleeds;
sleep problems (insomnia); or
muscle pain, back pain.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
 Sildenafil side effects (more detail)
