In-vitro study of lithium binding by sodium zirconium cyclosilicate (Lokelma®) or patiromer (Veltassa®)

Lithium poisoning remains common. Symptomatic lithium poisonings often require hemodialysis, especially when the patient has impaired renal function. An effective and non-invasive treatment to remove excess lithium would be desirable. We tested two recently approved, orally administered potassium binders in an in-vitro model. We used lithium-heparin tubes as both the source of lithium based prior studies showing the different volumes of serum in lithium-heparin tubes will produce apparent lithium concentrations in the range of toxicity (2.5 mmol/L and 5 mmol/L). We added three different volumes (0.5 mL, 0.75 mL, or 1.0 mL) of normal saline (NS) to the tubes. We calculated concentrations of sodium zirconium cyclosilicate (SZC, Lokelma®) and patiromer (Veltassa®) to simulate the ratio of drug to total body water for a 70 kg human. We prepared stock suspensions with different concentrations above and below the estimated ratios. We added varying concentrations of SZC or patiromer to tubes containing of NS. We measured sodium and lithium concentrations in duplicate for each concentration. Neither SZC nor patiromer reduced the lithium concentration across the range of concentrations in this in-vitro study.