Sodium zirconium cyclosilicate to increase lithium elimination

Abstract

Lithium is considered a mood stabilizer for bipolar affective disorders, but it has a narrow therapeutic index of 0.6-1.2 mEq/L. This can easily result in toxic levels after minimal changes in renal function or individual patient's pharmacokinetics. Lithium toxicity can arise with levels as low as 1.5 mEq, and there are limited therapeutic options to treat these patients presenting to the emergency department (ED). At therapeutic levels 95% of lithium is eliminated unchanged by the kidneys. However, previous literature has examined sodium polystyrene sulfonate (SPS) as an option to reduce lithium levels by binding the lithium cation and enhancing its excretion via the gastrointestinal tract. This suggests there may be an increased degree of non-renal clearance and altered toxicokinetics at supratherapeutic levels. However, SPS has been associated with intestinal necrosis and may cause treatment limiting hypokalemia, and is therefore not commonly recommended in treatment algorithms for lithium toxicity. A newer cation exchange resin, sodium zirconium cyclosilicate (SZC), may provide a safer alternative to SPS while also aiding in the clearance of lithium. We present a patient case where a patient with symptomatic acute-on-chronic lithium toxicity had increased clearance of lithium after a dose of SZC.

Keywords: Sodium zirconium cyclosilicate; lithium elimination; lithium toxicity; lithium toxicity treatment.