Long Term Oral Dantrolene Improved Muscular Symptoms in a Malignant Hyperthermia Susceptible Individual

Butala, B. N., Kang, A., Guron, J., & Brandom, B. W. (2016). Long term oral Dantrolene Improved Muscular Symptoms in a Malignant Hyperthermia Susceptible Individual. Journal of Neuromuscular Diseases, 3(1), 115–119. http://doi.org/10.3233/JND-150130

A recent case report presented a patient with a significant family history of MH who had frequent symptoms consistent with the skeletal muscle response seen in MH events. The most common triggers of an MH event are volatile anesthetic gases and the depolarizing muscle relaxant succinylcholine. Uncommon triggers, though confirmed in the literature include vigorous exercise and heat exposure.

The patient in this report had a sibling die during a minor surgery with exposure to a volatile anesthetic, an uncle died unexpectedly during an operation and an aunt died during childbirth in warm weather. This concerning family history prompted this patient to have specific MH testing performed. Test results were consistent with MH susceptibility (this was done prior to the more accurate testing available today). During the exam, the patient mentioned leg and calf muscle cramps as well as back pain affecting her sleep. The testing results, coupled with the patient’s symptoms resulted in the recommendation to take 25mg dantrolene daily by mouth.

Twenty Five years of follow up ensued. The patient reported resolution of symptoms 1-2 weeks after starting therapy. Her muscle cramps subsided, and her back pain improved which allowed her to get better sleep. Twice over the two and a half decades of follow up the patient had interruptions in her dantrolene medication. Each time she reported a return cramps and back pain, and each time the medication was restarted, symptoms resolved.

No medication is without risk. The more common side effects of dantrolene include drowsiness, dizziness, nausea, vomiting and weakness. It has also been associated with hepatic injury at chronically high doses. The patient studied had no increase in lab values that would indicate liver injury, she did however complain of gait instability if dantrolene was taken in the morning, so she opted to schedule her dose for bedtime which solved the instability.

This exciting report highlights the potential benefits for MH susceptible patients who are suffering from chronic muscle pain and cramps.

Brett Teodoro
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