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:
headache with chest pain and severe dizziness, fainting, fast or pounding heartbeats;
increased blood pressure--severe headache, buzzing in your ears, anxiety, confusion, shortness of breath; or
high levels of serotonin in the body--agitation, hallucinations, fever, fast heart rate, overactive reflexes, nausea, vomiting, diarrhea, loss of coordination, fainting.
Common side effects may include:
headache, weakness;
diarrhea, constipation;
stomach pain, indigestion, loss of appetite;
sleep problems (insomnia); or
fever, flu symptoms.
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.
 Granisetron side effects (more detail)
