Dantrolene

What it is used for

In Chronic Spasticity: Dantrolene sodium 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. Dantrolene sodium 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 dantrolene sodium.

Occasionally, subtle but meaningful improvement in spasticity may occur with dantrolene sodium 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 dantrolene sodium 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 dantrolene sodium 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 dantrolene sodium 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 dantrolene sodium should be administered following a malignant hyperthermic crisis to prevent recurrence of the signs of malignant hyperthermia.

Side effects, and when to stop

The most frequently occurring side effects of dantrolene sodium 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 dantrolene sodium therapy. If diarrhea recurs upon re-administration of dantrolene sodium, 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, pleural effusion with associated eosinophilia, anaphylaxis.

Other: Chills and fever.

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

For medical advice about adverse reactions contact your medical professional.

To report SUSPECTED ADVERSE REACTIONS, contact Amneal Pharmaceuticals at 1-877-835-5472 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

Who should not take it

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

Warnings

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

At the start of dantrolene sodium 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 dantrolene sodium 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 dantrolene sodium 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, dantrolene sodium should be discontinued. If caused by dantrolene sodium and detected early, the abnormalities in liver function characteristically have reverted to normal when the drug was discontinued.

Dantrolene sodium 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 dantrolene sodium 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.

Dantrolene sodium 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. Spontaneous reports suggest a higher proportion of hepatic events with fatal outcome in elderly patients receiving dantrolene sodium. However, the majority of these cases were complicated with confounding factors such as intercurrent illnesses and/or concomitant potentially hepatotoxic medications (see Geriatric Use subsection ).

Dantrolene sodium 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. Dantrolene sodium is associated with pleural effusion with associated eosinophilia. It should be used with caution in patients with a history of previous liver disease or dysfunction (see WARNINGS ).

Other medicines and interactions

Drowsiness may occur with dantrolene sodium 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 dantrolene sodium may potentiate vecuronium-induced neuromuscular block.

Storing it

Store at 20° to 25°C (68° to 77°F). Protect from moisture and humidity.

Dispense in a tightly-closed, light-resistant container (USP).