Precautions
General: Care must be taken to prevent extravasation of Dantrium® solution into the surrounding tissues due to the high pH of the intravenous formulation and potential for tissue necrosis.
When mannitol is used for prevention or treatment of late renal complications of malignant hyperthermia, the 3 g of mannitol needed to dissolve each 20 mg vial of i.v. Dantrium® should be taken into consideration.
Information for Patients: Based upon data in human volunteers, perioperatively, it is appropriate to tell patients who receive Dantrium® Intravenous that symptoms of muscle weakness should be expected postoperatively (i.e. decrease in grip strength and weakness of leg muscles, especially walking down stairs). In addition, symptoms such as “lightheadedness” may be noted. Since some of these symptoms may persist for up to 48 hours, patients must not operate an automobile or engage in other hazardous activity during this time. Caution is also indicated at meals on the day of administration because difficulty swallowing and choking has been reported. Caution should be exercised in the concomitant administration of tranquilizing agents.
Hepatotoxicity seen with Dantrium® Capsules: Dantrium® (dantrolene sodium) has a potential for hepatotoxicity, and should not be used in conditions other than those recommended.
Symptomatic hepatitis (fatal and non-fatal) has been reported at various dose levels of the drug. The incidence reported in patients taking up to 400 mg/day is much lower than in those taking doses of 800 mg or more per day. Even sporadic short courses of these higher dose levels within a treatment regimen markedly increased the risk of serious hepatic injury. Liver dysfunction as evidenced by blood chemical abnormalities alone (liver enzyme elevations) has been observed in patients exposed to Dantrium® for varying periods of time. Overt hepatitis has occurred at varying intervals after initiation of therapy, but has been most frequently observed between the third and twelfth month of therapy. The risk of hepatic injury appears to be greater in females, in patients over 35 years of age, and in patients taking other medication(s) in addition to Dantrium® (dantrolene sodium). Dantrium® should be used only in conjunction with appropriate monitoring of hepatic function including frequent determination of SGOT or SGPT.
Fatal and non-fatal liver disorders of an idiosyncratic or hypersensitivity type may occur with Dantrium® therapy.
Drug Interactions: Dantrium® is metabolized by the liver, and it is theoretically possible that its metabolism may be enhanced by drugs known to induce hepatic microsomal enzymes. However, neither phenobarbital nor diazepam appears to affect Dantrium® metabolism. Binding to plasma protein is not significantly altered by diazepam, diphenylhydantoin, or phenylbutazone. Binding to plasma proteins is reduced by warfarin and clofibrate and increased by tolbutamide.
Cardiovascular collapse in association with marked hyperkalemia has been reported in patients receiving dantrolene in combination with calcium channel blockers. It is recommended that the combination of intravenous dantrolene sodium and calcium channel blockers, such as verapamil, not be used together during the management of malignant hyperthermia crisis.
Administration of dantrolene may potentiate vecuronium-induced neuromuscular block.
For additional information please see Full Prescribing Information.