Case Presentation:
A 27 year-old male called 911 after intentional ingestion of 3g of lamotrigine and 3g of hydroxyzine. Upon arrival to the ER, approximately one hour after ingestion, the patient had slurred speech and was lethargic, but was able to provide his own history. The patient subsequently began to speak incoherently and became increasingly somnolent. An emergency room nurse reported possible seizure activity. Three hours after ingestion he did not respond to sternal rub and was intubated for airway protection. Initial arterial blood gas revealed acidosis of 7.28.
Infusion of 20% lipid emulsion was initiated six hours after ingestion- a 150mL bolus was given over 30 minutes followed by a rate of 50mL/hr for eight hours. The patient was kept on a continuous telemetry and no cardiac abnormalities were recorded. EEG did not reveal seizure activity. He was successfully extubated 24 hours after intubation. Lamotrigine levels were drawn and results (available two days later) showed an initial level of 19.8mg/L. The patient’s triglyceride level peaked at 768mg/dL just before discontinuation of the lipid emulsion. He had no permanent neurologic deficits and was discharged to an inpatient psychiatric facility.
Discussion:
Lamotrigine is a phenyltriazine medication that inhibits voltage-gated sodium channels to act as an anticonvulsant and mood stabilizer. Neurologic manifestations of lamotrigine toxicity (>14mg/L) can be as mild as delirium or agitation, but can progress to decreased consciousness or seizure activity. Reported cardiotoxic effects include QT prolongation, QRS prolongation, and complete heart block causing death.
Animal studies and case reports have provided convincing evidence for the infusion of lipid emulsion to reverse cardiac and neurotoxicity attributed to misapplication or overdose of local anesthetics. More recently, the infusion of lipid emulsion has been used as antidotal therapy in the management of drug overdoses caused by lipophilic drugs including antidepressants, antiepileptics, beta-blockers, and calcium channel blockers. Although the mechanism of action is not clear, it is postulated that the lipid emulsion creates a separate lipid compartment in the plasma, which draws the lipophilic drug out of the tissue. Side effects of lipid emulsion infusion include hypertriglyceridemia with the possibility of acute pancreatitis and inability to process lab values because of the chylous consistency of blood.
This case was submitted to the LIPAEMIC Report: Results of Clinical Use of Intravenous Lipid Emulsion in Drug Toxicity Online Lipid Registry. If added to the most recently published list of 48 uses, this case will be the first in this registry to report the use of lipid emulsion for lamotrigine toxicity.
Conclusions:
Lipid emulsion may be used in the management of overdose of various lipophilic drugs, which include beta-blockers, calcium channel blockers, tricyclic antidepressants, and various antipsychotics. Hospitalists should be aware that the administration of lipid emulsion can be performed as a part of cardiac resuscitation in patients with cardiac arrest, or can be used before cardiac abnormalities are present as an attempt to prevent progression to cardiac toxicity.