(996) Carisoprodol-Induced Status Epilepticus in a Young Adult With End-Stage Renal Disease

Introduction: This is a case of carisoprodol (Soma, MusFlex) toxicity, a muscle relaxant, that can be obtained without prescription outside the US. The exact mechanism is unknown, but it is thought to have both NMDA and GABA receptor activity. It undergoes hepatic metabolism, renal excretion, and not identified by most urine drug screens. Approximately 25% is metabolized into meprobamate, which has a 5x longer half-life and is 3x more potent. Severe toxicity, with large quantities or impaired clearance, leads to respiratory depression, seizures, and even death. Given global availability, improved awareness of the side effect profile may be lifesaving.

Description: A 29 year-old female with a history of hypertension and congenital renal hypoplasia requiring intermittent hemodialysis presented with lethargy and aphasia for 24 hours. She arrived from Honduras in her usual state of health two days prior with last dialysis the day before. She takes amlodipine, candesartan and family reported recent MusFlex (carisoprodol) use for lower back pain. On exam, she was obtunded but without focal deficits. CT and MRI Brain were unremarkable. She was admitted for undifferentiated encephalopathy, shortly after developed seizure like activity and was intubated for airway protection. EEG confirmed the presence of bilateral parieto-occipital epileptiform discharges and status epilepticus was diagnosed. She was loaded with levetiracetam and continued scheduled dosing. Empiric treatment for meningoencephalitis was initiated as well as emergent renal replacement therapy for drug clearance. Bloodwork, urine toxicology and lumbar puncture were unrevealing. With supportive treatment, her mentation gradually improved. She was extubated on day 6 and later discharged with full neurologic recovery.

Discussion: Carisoprodol is available under various formulations depending on location and packaging lacks safety information. It should be avoided in liver or kidney disease due to active metabolites. It is listed as a Schedule IV Substance by the DEA, defined as low potential for abuse. However, Norwegian and European medical authorities withdrew this medication due to the side effect profile. Medical providers must be aware of carisoprodol in new onset seizure or altered mental status differential.