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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 Laboratory monitoring should be frequent and the drug should be withdrawn immediately if there is any indication of recurrent liver involvement.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. Spontaneous reports suggest a higher proportion of hepatic events with fatal outcome in elderly patients receiving Dantrium. 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).
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 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 Category C: Pregnancy Category C: Adequate animal reproduction studies have not been conducted with Dantrium. It is also not known whether Dantrium can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. Dantrium should be given to a pregnant woman only if clearly needed.
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.
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.
Clinical studies of Dantrium did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience in the literature has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy. As with all patients receiving Dantrium, it is recommended that elderly patients receive the lowest dose compatible with the optimal response. Spontaneous reports suggest a higher proportion of hepatic events with fatal outcome in elderly patients receiving Dantrium. However, the majority of these cases were complicated with confounding factors such as intercurrent illnesses and/or concomitant potentially hepatotoxic medications (for hepatotoxicity details and its management see Black Box and WARNINGS Sections).
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. Dantrium 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).This monograph has been modified to include the generic and brand name in many instances.
Last reviewed on RxList: 7/25/2012
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