Assistant Clinical Professor Stanford University Medical Center
Introduction: Lamotrigine is a commonly used anticonvulsant in treating bipolar disorder. There is limited evidence on management of lamotrigine overdose, and this is the first case to describe the usage of continuous renal replacement therapy (CRRT) along with pharmacokinetics in a lamotrigine overdose.
Description: A 66-year-old male with chronic kidney disease stage 3 and bipolar disorder on lamotrigine was brought to hospital for unresponsiveness after a suspected ingestion of a 21g of lamotrigine in immediate release tablets. He was intubated and admitted to the intensive care unit. His first lamotrigine level was 42.3 ug/ml. Hemodialysis was started on hospital day 1; lamotrigine level decreased to 34.0 ug/ml immediately post-dialysis and his neurological exam improved. 2 hours after dialysis, the repeat lamotrigine level bounced back to 37.0 ug/ml. A second session of dialysis was performed on hospital day 2, and his post-dialysis level was 66.2 ug/ml. On hospital day 3, he developed an unstable wide-complex rhythm needing two vasopressors, and during that time, lamotrigine level was 66.9 ug/ml. 400 mEq sodium bicarbonate did not help with cardiac toxicity. 1.5 ml/kg of lipid emulsion bolus was given, followed by 0.25 ml/kg/min infusion for an hour. Shortly after lipid infusion was finished, the rhythm converted to a normal sinus rhythm. He was then started on CRRT, and 4.5 hours after CRRT initiation, his repeat lamotrigine level decreased to 52.5 ug/ml. On hospital day 4, intravenous rifampin 300mg every 8 hours was started to increase clearance of lamotrigine. His lamotrigine levels continued to downtrend and his neurological exam improved. On day 7, he was successfully extubated, and CRRT was discontinued. Lamotrigine was undetectable on day 9 and the patient was discharged to a psychiatric facility without neurological impairment on day 10.
Discussion: The rebound phenomenon of lamotrigine levels and its close correlation with symptom severity suggest the potential role of CRRT over intermittent hemodialysis in treating severe lamotrigine toxicity. CRRT could potentially avoid extreme level spikes, which are suspected to be due to delayed absorption from gut. Rifampin is another potential therapy, but its role remains undefined due to the concurrent use of CRRT.
