CYCLOBENZAPRINE OVERDOSE PRESENTING WITH RHABDOMYOLYSIS, DISTRIBUTIVE SHOCK, AND MULTIORGAN FAILURE

Abstract

SESSION TITLE: Medical Student/Resident Critical Care Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: October 18-21, 2020 INTRODUCTION: Few cases of cyclobenzaprine (CBZ) overdose exist in the literature, and the range of toxicity is not well-defined. We report a case of CBZ overdose with life-threatening shock and multiorgan failure. CASE PRESENTATION: A 51-year-old woman with type 2 diabetes, hypertension, chronic back pain, and depression presented to the emergency department after being found unresponsive near an empty bottle of CBZ. She was hypotensive and mildly tachycardic with a Glasgow coma score of 8. She was intubated and admitted to the intensive care unit. She had multiorgan failure with acute kidney injury (blood urea nitrogen: 57 mg/dL, creatinine: 7.1 mg/dL), elevated liver enzymes, anion gap metabolic acidosis (arterial blood gas pH 7.1, pCO2: 34, pO2: 80, HCO3: 10), creatine kinase level of 39K IU/L, and myoglobin >3000 ng/mL. Her urine drug screen was positive for TCA; her serum qualitative screen was positive for CBZ. Her electrocardiogram (ECG) showed widened QRS with no acute ST changes. Given her hypotension refractory to intravenous (IV) fluid resuscitations, she received 2 inotropic agents for 2 days, maintenance IV fluids, and NaHCO3 infusion. Her QRS interval normalized after 6 hours. She was extubated on day 3 with subsequent normalization of both her kidney and liver functions (Graph 1, 2). Later she reported ingesting the CBZ as a suicide attempt. DISCUSSION: Cyclobenzaprine is a centrally acting muscle relaxant, that is structurally similar to amitriptyline (TCA), differing by only one double bond. CBZ and TCA cause reserpine antagonism, norepinephrine potentiation, potent peripheral and central anticholinergic effects, and sedation. Toxic effects can be mild (e.g., confusion, visual hallucination, agitation, drowsiness, dry mouth, dizziness) or severe (e.g., cardiac arrhythmias, hypotension, convulsions, stupor, coma). Spiller et al.'s analysis of 402 cases of CBZ toxicity found respiratory failure requiring mechanical ventilation in 12 cases (3%). Only 2 cases had refractory hypotension requiring inotropic support. Rhabdomyolysis is an uncommon complication, reported only in 2 independent case reports. The management of a CBZ overdose is like that of any TCA. Gastrointestinal decontamination by lavage and activated charcoal is time sensitive. QRS widening or intraventricular conduction abnormalities should be treated with NaHCO3. CONCLUSIONS: To our knowledge, this is the first case report of life-threatening shock resulting in concurrent multiorgan failure, including acute renal insufficiency, hepatic injury, rhabdomyolysis, metabolic encephalopathy, and respiratory failure from CBZ overdose. Health care professionals should realize that CBZ overdose can present as a spectrum of toxicities, including life-threatening complications. Early recognition and appropriate intervention can help reverse this otherwise possible fatal condition Reference #1: Spiller HA, Winter ML, Mann KV, Borys DJ, Muir S, Krenzelok EP. Five-year multicenter retrospective review of cyclobenzaprine toxicity. J Emerg Med. 1995;13(6):781–785. doi:10.1016/0736-4679(95)02019-5 Reference #2: Chabria SB. Rhabdomyolysis: a manifestation of cyclobenzaprine toxicity. J Occup Med Toxicol. 2006;1:16. doi:10.1186/1745-6673-1-16 DISCLOSURES: No relevant relationships by Meily Arevalo, source=Web Response No relevant relationships by Mohamed Elmassry, source=Web Response No relevant relationships by John Makram, source=Web Response No relevant relationships by Haneen Mallah, source=Web Response No relevant relationships by Arunee Motes, source=Web Response No relevant relationships by Kenneth Nugent, source=Web Response No relevant relationships by Pablo Paz, source=Web Response