The chemical formula of Dantrium (dantrolene sodium) is hydrated 1-[[[5-(4- nitrophenyl)-2-furanyl]methylene]amino]-2, 4-imidazolidinedione sodium salt. It is an orange powder, slightly soluble in water, but due to its slightly acidic nature the solubility increases somewhat in alkaline solution. The anhydrous salt has a molecular weight of 336. The hydrated salt contains approximately 15% water (3-½ moles) and has a molecular weight of 399. The structural formula for the hydrated salt is:

Dantrium is supplied in capsules of 25 mg, 50 mg, and 100 mg.

Inactive Ingredients: Each capsule contains edible black ink, FD&C Yellow No. 6, gelatin, lactose, magnesium stearate, starch, synthetic iron oxide red, synthetic iron oxide yellow, talc, and titanium dioxide.

In Chronic Spasticity: Dantrium is indicated in controlling the manifestations of clinical spasticity resulting from upper motor neuron disorders (e.g., spinal cord injury, stroke, cerebral palsy, or multiple sclerosis). It is of particular benefit to the patient whose functional rehabilitation has been retarded by the sequelae of spasticity. Such patients must have presumably reversible spasticity where relief of spasticity will aid in restoring residual function. Dantrium is not indicated in the treatment of skeletal muscle spasm resulting from rheumatic disorders.

If improvement occurs, it will ordinarily occur within the dosage titration (See DOSAGE AND ADMINISTRATION), and will be manifested by a decrease in the severity of spasticity and the ability to resume a daily function not quite attainable without Dantrium.

Occasionally, subtle but meaningful improvement in spasticity may occur with Dantrium therapy. In such instances, information regarding improvement should be solicited from the patient and those who are in constant daily contact and attendance with him. Brief withdrawal of Dantrium for a period of 2 to 4 days will frequently demonstrate exacerbation of the manifestations of spasticity and may serve to confirm a clinical impression.

A decision to continue the administration of Dantrium on a long-term basis is justified if introduction of the drug into the patient's regimen:

produces a significant reduction in painful and/or disabling spasticity such as clonus, or

permits a significant reduction in the intensity and/or degree of nursing care required, or

rids the patient of any annoying manifestation of spasticity considered important by the patient himself.

In Malignant Hyperthermia: Oral Dantrium is also indicated preoperatively to prevent or attenuate the development of signs of malignant hyperthermia in known, or strongly suspect, malignant hyperthermia susceptible patients who require anesthesia and/or surgery. Currently accepted clinical practices in the management of such patients must still be adhered to (careful monitoring for early signs of malignant hyperthermia, minimizing exposure to triggering mechanisms and prompt use of intravenous dantrolene sodium and indicated supportive measures should signs of malignant hyperthermia appear); see also the package insert for Dantrium® (dantrolene sodium) Intravenous.

Oral Dantrium should be administered following a malignant hyperthermic crisis to prevent recurrence of the signs of malignant hyperthermia.

For Use in Chronic Spasticity: Prior to the administration of Dantrium, consideration should be given to the potential response to treatment. A decrease in spasticity sufficient to allow a daily function not otherwise attainable should be the therapeutic goal of treatment with Dantrium. Refer to INDICATIONS AND USAGE section for description of response to be anticipated.

It is important to establish a therapeutic goal (regain and maintain a specific function such as therapeutic exercise program, utilization of braces, transfer maneuvers, etc.) before beginning Dantrium therapy. Dosage should be increased until the maximum performance compatible with the dysfunction due to underlying disease is achieved. No further increase in dosage is then indicated.

Usual Dosage: It is important that the dosage be titrated and individualized for maximum effect. The lowest dose compatible with optimal response is recommended.

In view of the potential for liver damage in long-term Dantrium use, therapy should be stopped if benefits are not evident within 45 days.

Adults: The following gradual titration schedule is suggested. Some patients will not respond until higher daily dosage is achieved. Each dosage level should be maintained for seven days to determine the patient's response. If no further benefit is observed at the next higher dose, dosage should be decreased to the previous lower dose.

25 mg once daily for seven days, then
25 mg t.i.d. for seven days
50 mg t.i.d. for seven days
100 mg t.i.d.

Therapy with a dose four times daily may be necessary for some individuals. Doses higher than 100 mg four times daily should not be used. (See Box Warning.)

Pediatric Patients: The following gradual titration schedule is suggested. Some patients will not respond until higher daily dosage is achieved. Each dosage level should be maintained for seven days to determine the patient's response. If no further benefit is observed at the next higher dose, dosage should be decreased to the previous lower dose.

0.5 mg/kg once daily for seven days, then
0.5 mg/kg t.i.d. for seven days
1 mg/kg t.i.d. for seven days
2 mg/kg t.i.d.

Therapy with a dose four times daily may be necessary for some individuals. Doses higher than 100 mg four times daily should not be used. (See Box Warning.)

For Malignant Hyperthermia:

Preoperatively: Administer 4 to 8 mg/kg/day of oral Dantrium in 3 or 4 divided doses for one or two days prior to surgery, with the last dose being given approximately 3 to 4 hours before scheduled surgery with a minimum of water.

This dosage will usually be associated with skeletal muscle weakness and sedation (sleepiness or drowsiness); adjustment can usually be made within the recommended dosage range to avoid incapacitation or excessive gastrointestinal irritation (including nausea and/or vomiting).

Post Crisis Follow-up: Oral Dantrium should also be administered following a malignant hyperthermia crisis, in doses of 4 to 8 mg/kg per day in four divided doses, for a one to three day period to prevent recurrence of the manifestations of malignant hyperthermia.

Dantrium (dantrolene sodium) is available in:

25-mg opaque, orange and tan capsules:

NDC 0149-0030-05 bottle of 100
NDC 0149-0030-66 bottle of 500

50-mg opaque, orange and tan capsules:

NDC 0149-0031-05 bottle of 100

100-mg opaque, orange and tan capsules:

NDC 0149-0033-05 bottle of 100

Avoid excessive heat (over 104°F or 40°C).

Address medical inquiries to Procter & Gamble Pharmaceuticals, Medical Communications Department, PO Box 8006, Mason, Ohio 45040-8006. REVISED SEPTEMBER 2002. FDA rev date: 10/31/1997

The most frequently occurring side effects of Dantrium have been drowsiness, dizziness, weakness, general malaise, fatigue, and diarrhea. These are generally transient, occurring early in treatment, and can often be obviated by beginning with a low dose and increasing dosage gradually until an optimal regimen is established. Diarrhea may be severe and may necessitate temporary withdrawal of Dantrium therapy. If diarrhea recurs upon readministration of Dantrium, therapy should probably be withdrawn permanently.

Other less frequent side effects, listed according to system, are:

Gastrointestinal: Constipation, rarely progressing to signs of intestinal obstruction, GI bleeding, anorexia, swallowing difficulty, gastric irritation, abdominal cramps, nausea and/or vomiting.

Hepatobiliary: Hepatitis (see WARNINGS).

Neurologic: Speech disturbance, seizure, headache, light-headedness, visual disturbance, diplopia, alteration of taste, insomnia, drooling.

Cardiovascular: Tachycardia, erratic blood pressure, phlebitis, heart failure.

Hematologic: Aplastic anemia, anemia, leukopenia, lymphocytic lymphoma, thrombocytopenia.

Psychiatric: Mental depression, mental confusion, increased nervousness.

Urogenital: Increased urinary frequency, crystalluria, hematuria, difficult erection, urinary incontinence and/or nocturia, difficult urination and/or urinary retention.

Integumentary: Abnormal hair growth, acne-like rash, pruritus, urticaria, eczematoid eruption, sweating.

Musculoskeletal: Myalgia, backache.

Respiratory: Feeling of suffocation, respiratory depression.

Special Senses: Excessive tearing.

Hypersensitivity: Pleural effusion with pericarditis, anaphylaxis.

Other: Chills and fever.

The published literature has included some reports of Dantrium use in patients with Neuroleptic Malignant Syndrome (NMS). Dantrium capsules are not indicated for the treatment of NMS and patients may expire despite treatment with Dantrium capsules.

Drug Abuse and Dependence

Drug abuse and dependency potential has not been evaluated in human or animal studies.

Drowsiness may occur with Dantrium therapy, and the concomitant administration of CNS depressants such as sedatives and tranquilizing agents may result in further drowsiness.

While a definite drug interaction with estrogen therapy has not yet been established, caution should be observed if the two drugs are to be given concomitantly. Hepatotoxicity has occurred more often in women over 35 years of age receiving concomitant estrogen therapy.

Cardiovascular collapse in patients treated simultaneously with verapamil and dantrolene sodium is rare. The combination of therapeutic doses of intravenous dantrolene sodium and verapamil in halothane/α-chloralose anesthetized swine has resulted in ventricular fibrillation and cardiovascular collapse in association with marked hyperkalemia. Until the relevance of these findings to humans is established, the combination of dantrolene sodium and calcium channel blockers is not recommended during the management of malignant hyperthermia.

Administration of Dantrium may potentiate vecuronium-induced neuromuscular block.

It is important to recognize that fatal and non-fatal liver disorders of an idiosyncratic or hypersensitivity type may occur with Dantrium therapy.

At the start of Dantrium therapy, it is desirable to do liver function studies (SGOT, SGPT, alkaline phosphatase, total bilirubin) for a baseline or to establish whether there is pre-existing liver disease. If baseline liver abnormalities exist and are confirmed, there is a clear possibility that the potential for Dantrium hepatotoxicity could be enhanced, although such a possibility has not yet been established.

Liver function studies (e.g., SGOT or SGPT) should be performed at appropriate intervals during Dantrium therapy. If such studies reveal abnormal values, therapy should generally be discontinued. Only where benefits of the drug have been of major importance to the patient, should reinitiation or continuation of therapy be considered. Some patients have revealed a return to normal laboratory values in the face of continued therapy while others have not.

If symptoms compatible with hepatitis, accompanied by abnormalities in liver function tests or jaundice appear, Dantrium should be discontinued. If caused by Dantrium and detected early, the abnormalities in liver function characteristically have reverted to normal when the drug was discontinued. Dantrium therapy has been reinstituted in a few patients who have developed clinical and/or laboratory evidence of hepatocellular injury. If such reinstitution of therapy is done, it should be attempted only in patients who clearly need Dantrium and only after previous symptoms and laboratory abnormalities have cleared. The patient should be hospitalized and the drug should be restarted in very small and gradually increasing doses. Laboratory monitoring should be frequent and the drug should be withdrawn immediately if there is any indication of recurrent liver involvement. Some patients have reacted with unmistakable signs of liver abnormality upon administration of a challenge dose, while others have not.

Dantrium should be used with particular caution in females and in patients over 35 years of age in view of apparent greater likelihood of drug-induced, potentially fatal, hepatocellular disease in these groups.

Carcinogenesis, Mutagenesis, Impairment of Fertility: Long-term safety of Dantrium in humans has not been established. Chronic studies in rats, dogs, and monkeys at dosages greater than 30 mg/kg/day showed growth or weight depression and signs of hepatopathy and possible occlusion nephropathy, all of which were reversible upon cessation of treatment. Sprague-Dawley female rats fed dantrolene sodium for 18 months at dosage levels of 15, 30, and 60 mg/kg/day showed an increased incidence of benign and malignant mammary tumors compared with concurrent controls. At the highest dose level, there was an increase in the incidence of benign hepatic lymphatic neoplasms. In a 30- month study at the same dose levels also in Sprague-Dawley rats, dantrolene sodium produced a decrease in the time of onset of mammary neoplasms. Female rats at the highest dose level showed an increased incidence of hepatic lymphangiomas and hepatic angiosarcomas.

The only drug-related effect seen in a 30-month study in Fischer-344 rats was a dose-related reduction in the time of onset of mammary and testicular tumors. A 24-month study in HaM/ICR mice revealed no evidence of carcinogenic activity. Carcinogenicity in humans cannot be fully excluded, so that this possible risk of chronic administration must be weighed against the benefits of the drug (i.e., after a brief trial) for the individual patient.

Dantrolene sodium has produced positive results in the Ames S. Typhimurium bacterial mutagenesis assay in the presence and absence of a liver activating system.

Pregnancy: Pregnancy Category C: Dantrium has been shown to be embryocidal in the rabbit and has been shown to decrease pup survival in the rat when given at doses seven times the human oral dose. There are no adequate and well-controlled studies in pregnant women (see Labor and Delivery subheading for information regarding placental transfer of the drug). Dantrium capsules should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Labor and Delivery: In one non-randomized open-label study, 21 term pregnant patients received prophylactic oral Dantrium 100 mg per day for 2 to 10 days prior to delivery. Dantrolene readily crossed the placenta with maternal and fetal whole blood levels approximately equal at delivery; neonatal levels then fell approximately 50% per day for 2 days before declining sharply. No neonatal respiratory and neuromuscular side effects were detected at low dose. More data, at higher doses, are needed before more definitive conclusions can be made.

Nursing Mothers: Dantrium should not be used in nursing mothers.

Usage in Pediatric Patients: The long-term safety of Dantrium in pediatric patients under the age of 5 years has not been established. Because of the possibility that adverse effects of the drug could become apparent only after many years, a benefit-risk consideration of the long-term use of Dantrium is particularly important in pediatric patients.

Dantrium should be used with caution in patients with impaired pulmonary function, particularly those with obstructive pulmonary disease, and in patients with severely impaired cardiac function due to myocardial disease. It should be used with caution in patients with a history of previous liver disease or dysfunction (see WARNINGS).

Symptoms which may occur in case of overdose include, but are not limited to, muscular weakness and alterations in the state of consciousness (e.g. lethargy, coma), vomiting, diarrhea, and crystalluria. For acute overdose, general supportive measures should be employed along with immediate gastric lavage.

Intravenous fluids should be administered in fairly large quantities to avert the possibility of crystalluria. An adequate airway should be maintained and artificial resuscitation equipment should be at hand. Electrocardiographic monitoring should be instituted, and the patient carefully observed. To date, no experience has been reported with dialysis and its value in Dantrium overdose is not known.

Active hepatic disease, such as hepatitis and cirrhosis, is a contraindication for use of Dantrium. Dantrium is contraindicated where spasticity is utilized to sustain upright posture and balance in locomotion or whenever spasticity is utilized to obtain or maintain increased function.

In isolated nerve-muscle preparation, Dantrium has been shown to produce relaxation by affecting the contractile response of the skeletal muscle at a site beyond the myoneural junction, directly on the muscle itself. In skeletal muscle, Dantrium dissociates the excitation-contraction coupling, probably by interfering with the release of Ca++ from the sarcoplasmic reticulum. This effect appears to be more pronounced in fast muscle fibers as compared to slow ones, but generally affects both. A central nervous system effect occurs, with drowsiness, dizziness, and generalized weakness occasionally present. Although Dantrium does not appear to directly affect the CNS, the extent of its indirect effect is unknown. The absorption of Dantrium after oral administration in humans is incomplete and slow but consistent, and dose-related blood levels are obtained. The duration and intensity of skeletal muscle relaxation is related to the dosage and blood levels. The mean biologic half-life of Dantrium in adults is 8.7 hours after a 100-mg dose. Specific metabolic pathways in the degradation and elimination of Dantrium in human subjects have been established. Metabolic patterns are similar in adults and pediatric patients. In addition to the parent compound, dantrolene, which is found in measurable amounts in blood and urine, the major metabolites noted in body fluids are the 5-hydroxy analog and the acetamido analog. Since Dantrium is probably metabolized by hepatic microsomal enzymes, enhancement of its metabolism by other drugs is possible. However, neither phenobarbital nor diazepam appears to affect Dantrium metabolism.

Clinical experience in the management of fulminant human malignant hyperthermia, as well as experiments conducted in malignant hyperthermia susceptible swine, have revealed that the administration of intravenous dantrolene, combined with indicated supportive measures, is effective in reversing the hypermetabolic process of malignant hyperthermia. Known differences between human and swine malignant hyperthermia are minor. The prophylactic administration of oral or intravenous dantrolene to malignant hyperthermia susceptible swine will attenuate or prevent the development of signs of malignant hyperthermia in a manner dependent upon the dosage of dantrolene administered and the intensity of the malignant hyperthermia triggering stimulus. Limited clinical experience with the administration of oral dantrolene to patients judged malignant hyperthermia susceptible, when combined with clinical experience in the use of intravenous dantrolene for the treatment of malignant hyperthermia and data derived from the above cited animal model experiments, suggests that oral dantrolene will also attenuate or prevent the development of signs of human malignant hyperthermia, provided that currently accepted practices in the management of such patients are adhered to (see INDICATIONS AND USAGE); intravenous dantrolene should also be available for use should the signs of malignant hyperthermia appear.

Patients should be cautioned against driving a motor vehicle or participating in hazardous occupations while taking Dantrium. Caution should be exercised in the concomitant administration of tranquilizing agents.

Dantrium might possibly evoke a photosensitivity reaction; patients should be cautioned about exposure to sunlight while taking it.

IMPORTANT NOTE: This is a summary and does not contain all possible information about this product. For complete information about this product or your specific health needs, ask your health care professional. Always seek the advice of your health care professional if you have any questions about this product or your medical condition. This information is not intended as individual medical advice and does not substitute for the knowledge and judgment of your health care professional. This information does not contain any assurances that this product is safe, effective, or appropriate for you.

DANTROLENE - ORAL

(DAN-trow-leen)

COMMON BRAND NAME(S): Dantrium

WARNING: Infrequently, dantrolene may cause very serious (possibly fatal) liver problems. The risk is greater if you use high doses of dantrolene (over 400-800 milligrams per day), or are female, older than 35 years, or taking other medications. Signs of liver problems usually appear between 3-12 months of treatment. To reduce your risk of this side effect, you should have regular liver tests checked by your doctor. Tell your doctor immediately if you develop any of the following symptoms of liver disease: persistent nausea/vomiting, stomach/abdominal pain, dark urine, yellowing eyes/skin, unusual tiredness.

To further reduce your risk of side effects, do not increase your dose or take it more often or for longer than prescribed. The lowest effective dose should be used. The manufacturer recommends that if your condition does not improve after 45 days of treatment, your doctor must be notified and dantrolene should be stopped.

USES: 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.

OTHER USES: This section contains uses of this drug that are not listed in the approved professional labeling for the drug but that may be prescribed by your health care professional. Use this drug for a condition that is listed in this section only if it has been so prescribed by your health care professional.

This drug may also be used to treat a certain uncommon condition (neuroleptic malignant syndrome) involving muscle stiffness, fever, and fast heartbeat caused by psychiatric medications.

HOW TO USE: See also Warning section.

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.

SIDE EFFECTS: See also Warning section.

Drowsiness, dizziness, weakness, tiredness, nausea, and diarrhea may occur as your body adjusts to this medication and usually lessen after several days. Headache, constipation, slurred speech, and drooling may also occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor immediately if any of these unlikely but serious side effects occur: sunburn (sun sensitivity), vision changes, black/tarry stools, vomit that looks like coffee grounds, mental/mood changes, trouble swallowing, problems with urination, severe/persistent constipation, seizures, fast heartbeat.

Tell your doctor immediately if any of these rare but very serious side effects occur: easy bruising/bleeding, signs of infection (e.g., fever, chills, persistent sore throat), chest pain, swelling of the ankles/feet, trouble breathing.

A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any symptoms of a serious allergic reaction, including: rash, itching, swelling, severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

Contact your doctor for medical advice about side effects. The following numbers do not provide medical advice, but in the US you may report side effects to the Food and Drug Administration (FDA) at 1-800-FDA-1088. In Canada, you may call Health Canada at 1-866-234-2345.

PRECAUTIONS: Before taking dantrolene, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies.

This medication should not be used if you have certain medical conditions. Before using this medicine, consult your doctor or pharmacist if you have: liver problems (e.g., hepatitis, cirrhosis).

Before using this medication, tell your doctor or pharmacist your medical history, especially of: breathing problems (e.g., chronic obstructive pulmonary disease-COPD), heart problems.

This drug may make you dizzy or drowsy. Use caution while driving, using machinery, or doing any activity that requires alertness. Limit alcoholic beverages.

This medication may make you more sensitive to the sun. Avoid prolonged sun exposure, tanning booths, and sunlamps. Use a sunscreen and wear protective clothing when outdoors.

Before having surgery, tell your doctor or dentist that you are using this medication.

During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.

This drug passes into breast milk and could have undesirable effects on a nursing infant. Therefore, breast-feeding is not recommended while using this drug. Consult your doctor before breast-feeding.

DRUG INTERACTIONS: Your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor or pharmacist first.

Before using this medication, tell your doctor or pharmacist of all prescription and nonprescription/herbal products you may use, especially of: estrogen.

Tell your doctor or pharmacist if you also take drugs that cause drowsiness such as: certain antihistamines (e.g., diphenhydramine), anti-seizure drugs (e.g., carbamazepine), medicine for sleep or anxiety (e.g., alprazolam, diazepam, zolpidem), other muscle relaxants, narcotic pain relievers (e.g., codeine), psychiatric medicines (e.g., chlorpromazine, risperidone, amitriptyline, trazodone).

Check the labels on all your medicines (e.g., cough-and-cold products) because they may contain drowsiness-causing ingredients. Ask your pharmacist about using those products safely.

This document does not contain all possible interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist.

OVERDOSE: If overdose is suspected, contact your local poison control center or emergency room immediately. US residents should call the US National Poison Hotline at 1-800-222-1222. Canada residents should call a provincial poison control center. Symptoms of overdose may include: severe muscle weakness, severe tiredness, severe drowsiness.

NOTES: Do not share this medication with others.

Laboratory and/or medical tests (e.g., liver function tests) should be performed periodically to check for side effects. Consult your doctor for more details.

MISSED DOSE: If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose and resume your usual dosing schedule. Do not double the dose to catch up.

STORAGE: Store at room temperature between 59-86 degrees F (15-30 degrees C) away from light, moisture, and heat. Do not store in the bathroom. Keep all medicines away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company for more details about how to safely discard your product.

MEDICAL ALERT: Your condition can cause complications in a medical emergency. For information about enrolling in MedicAlert, call 1-800-854-1166 (USA) or 1-800-668-1507 (Canada).

Information last revised July 2008 Copyright(c) 2008 First DataBank, Inc.