Get emergency medical help if you have signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.
Call your doctor at once if you have:
fast or pounding heartbeats;
fluttering in your chest, shortness of breath, and sudden dizziness (like you might pass out);
slow heart rate, weak pulse, slow breathing (breathing may stop);
feeling short of breath;
swelling, rapid weight gain;
pale skin, easy bruising or bleeding, unusual weakness;
fever, flu-like symptoms; or
jaundice (yellowing of the skin or eyes).
Common side effects may include:
dizziness;
vision problems;
trouble breathing;
headache;
nausea; or
feeling weak or tired.
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.
 Flecainide side effects (more detail)
