Hepatotoxicity

• This drug has the potential for hepatotoxicity, and should not be used in conditions other than those recommended.
• Symptomatic hepatitis (fatal and nonfatal) has been reported at various dose levels of the drug. The incidence reported in patients taking up to 400 mg daily is much lower than in those taking doses of 800 mg or more daily. Even sporadic short courses of these higher dose levels markedly increase the risk of serious hepatic injury.
• Liver dysfunction may be evidenced by chemical blood abnormalities alone (liver enzyme elevations) in patients taking dantrolene 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 12th month of therapy.
• The risk of hepatic injury is increased in females, patients over 35 yrs of age, and in patients on concurrent pharmacotherapy.
• This drug should be used only with appropriate monitoring of hepatic function, including frequent determination of AGOT or AGPT. If no observable benefit is derived from the administration of this drug after 45 days, therapy should be discontinued, 
• The lowest possible effective dose should be used.