What side effects may I notice from receiving Dantrolene?

Side effects that you should report to your doctor or health care professional as soon as possible:

-allergic reactions like skin rash, itching or hives, swelling of the face, lips, or tongue
-breathing problems
-seizures
-signs and symptoms of liver injury like dark yellow or brown urine; general ill feeling or flu-like symptoms; light-colored stools; loss of appetite; nausea; right upper belly pain; unusually weak or tired; yellowing of the eyes or skin
-unusually weak or tired

Side effects that usually do not require medical attention (report to your doctor or health care professional if they continue or are bothersome):

-constipation
-dizziness
-nausea, vomiting
-pain, redness, or irritation at site where injected
-trouble speaking

This list may not describe all possible side effects for Dantrolene. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.