Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat. Stop using dextromethorphan and call your doctor at once if you have any of these serious side effects:
severe dizziness, anxiety, restless feeling, or nervousness;
seizures or convulsions;
confusion, hallucinations; or
slow, shallow breathing.
Less serious side effects are more likely, such as stomach upset.
This is not a complete list of dextromethorphan 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.
 Dextromethorphan side effects (more detail)
