This medication is used to treat muscle tightness and cramping (spasms) caused by certain nerve disorders such as spinal cord injury, stroke, cerebral palsy, and multiple sclerosis. It works by relaxing the muscles. Dantrolene helps reduce muscle pain and stiffness, improves your ability to move around, and lets you do more of your daily activities.

Dantrolene is also used with other treatments to prevent or treat special cases of high fever (malignant hyperthermia) related to anesthesia and surgery.

Take this medication by mouth as directed by your doctor. For the treatment of long-term muscle tightness/spasms, your doctor may slowly increase your dose to lower your chance of side effects until the right dose for you is determined. The manufacturer recommends that you do not take more than 400 milligrams per day.

Dosage is based on your medical condition, response to therapy, and in some cases weight. For the prevention and treatment of malignant hyperthermia, treatment lasts for several days.

Take this medication regularly to get the most benefit from it. To help you remember, take it at the same times each day.

Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

• Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
• Signs of liver problems like dark urine, feeling tired, not hungry, upset stomach or stomach pain, light-colored stools, throwing up, or yellow skin or eyes.
• Choking.
• Trouble swallowing.
• Chest pain or pressure.
• Shortness of breath.

Tell all of your health care providers that you take Dantrium (dantrolene capsules). This includes your doctors, nurses, pharmacists, and dentists.

Avoid driving and doing other tasks or actions that call for you to be alert until you see how Dantrium (dantrolene capsules) affects you.

This medicine may make you sunburn more easily. Use care if you will be in the sun. Tell your doctor if you sunburn easily while taking this drug.

Talk with your doctor before you drink alcohol or use other drugs and natural products that slow your actions.

Very bad and sometimes deadly allergic side effects have rarely happened. Talk with your doctor.

If you are 65 or older, use Dantrium (dantrolene capsules) with care. You could have more side effects.

Tell your doctor if you are pregnant or plan on getting pregnant. You will need to talk about the benefits and risks of using Dantrium (dantrolene capsules) while you are pregnant.

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:

• Feeling sleepy.
• Dizziness.
• Feeling tired or weak.
• Diarrhea.

These are not all of the side effects that may occur. If you have questions about side effects, call your doctor. Call your doctor for medical advice about side effects.

What should I tell my health care provider before I take this medicine?

They need to know if you have any of these conditions:

• heart disease
• liver disease
• lung or breathing disease, like asthma
• an unusual or allergic reaction to dantrolene, other medicines, foods, dyes, or preservatives
• pregnant or trying to get pregnant
• breast-feeding

How should I use this medicine?

Take this medicine by mouth with a glass of water. Follow the directions on the prescription label. Take your doses at regular intervals. Do not take your medicine more often than directed.

Talk to your pediatrician regarding the use of this medicine in children. While this drug may be prescribed for selected conditions, precautions do apply.

What if I miss a dose?

If you miss a dose, take it as soon as you can. If it is almost time for your next dose, take only that dose. Do not take double or extra doses.

What may interact with this medicine?

Do not take this medication with any of the following medicines:

• narcotic medicines for cough

This medicine may also interact with the following medications:

• alcohol
• antihistamines for allergy, cough and cold
• certain medicines for anxiety or sleep
• certain medicines for blood pressure, heart disease, irregular heart beat
• certain medicines for depression like amitriptyline, fluoxetine, sertraline
• certain medicines for seizures like phenobarbital, primidone
• female hormones, like estrogens or progestins and birth control pills, patches, rings, or injections
• general anesthetics like halothane, isoflurane, methoxyflurane, propofol
• local anesthetics like lidocaine, pramoxine, tetracaine
• medicines that relax muscles for surgery
• narcotic medicines for pain
• phenothiazines like chlorpromazine, mesoridazine, prochlorperazine, thioridazine