When This Medicine Should Not Be Used:
This medicine is not right for everyone. You should not use it if you had an allergic reaction to dantrolene, or if you have active liver disease (such as hepatitis or cirrhosis).

How to Use This Medicine:
Capsule

• Take your medicine as directed. Your dose may need to be changed several times to find what works best for you.
• Missed dose: Take a dose as soon as you remember. If it is almost time for your next dose, wait until then and take a regular dose. Do not take extra medicine to make up for a missed dose.
• Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light.

Drugs and Foods to Avoid:
Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

• Some medicines can affect how dantrolene works. Tell your doctor if you are also using any of the following:
  
  • Estrogen
  • Heart or blood pressure medicine
• Tell your doctor if you use anything else that makes you sleepy. Some examples are allergy medicine, narcotic pain medicine, and alcohol.

Warnings While Using This Medicine:

• Tell your doctor if you are pregnant or breastfeeding, or if you have a history of liver disease, heart disease, or lung disease.
• This medicine can cause the following problems:
  
  • Liver problems
• Your doctor will do lab tests at regular visits to check on the effects of this medicine. Keep all appointments.
• This medicine may make you dizzy or drowsy. Do not drive or do anything else that could be dangerous if you are not alert.
• This medicine may make your skin more sensitive to sunlight. Wear sunscreen. Do not use sunlamps or tanning beds.
• Keep all medicine out of the reach of children. Never share your medicine with anyone.

Possible Side Effects While Using This Medicine:
Call your doctor right away if you notice any of these side effects:

• Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
• Dark urine or pale stools, nausea, vomiting, loss of appetite, stomach pain, yellow skin or eyes
• Fast, pounding, or uneven heartbeat, chest pain, trouble breathing
• Severe diarrhea

If you notice these less serious side effects, talk with your doctor:

• Dizziness, drowsiness, lightheadedness
• Mild diarrhea
• Muscle weakness, tiredness

If you notice other side effects that you think are caused by this medicine, tell your doctor.
Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088