Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Call your doctor at once if you have:
wheezing, choking, or other breathing problems after using  Xopenex HFA;
pounding heartbeats or fluttering in your chest;
worsening asthma symptoms; or
low potassium--leg cramps, constipation, irregular heartbeats, fluttering in your chest, extreme thirst, increased urination, numbness or tingling, muscle weakness or limp feeling.
Common side effects may include:
dizziness, nervousness, tremors;
runny nose, sore throat;
chest pain or tightness, irregular heartbeats;
pain; or
vomiting.
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.
 Xopenex HFA side effects (more detail)
