Context: Lithium (Li) is a first-line treatment for bipolar disorder but has a narrow therapeutic index. Treatment of Li toxicity includes supportive measures and hemodialysis in severe cases, but this modality is not always immediately available. Sodium polystyrene sulfonate (SPS, Kayexalate), a cation exchanger, has been promising in animal models and human reports to reduce absorption and enhance elimination of Li.
Material and methods: A retrospective cohort study was conducted. All cases of chronic Li intoxication were reviewed in two adult-care hospitals from 2000 to 2009. A group comparison and a within-patient comparison were performed to compare the effect of SPS on the median Li half-life (T(1/2)). For this study, at least three serum Li levels were required for T(1/2) calculations.
Results: Forty-eight patients met inclusion requirements, 12 of whom had taken SPS. Median Li T(1/2) in the treated and control groups was 20.5 and 43.2 hours, respectively (p = 0.0006). In the 12 treated patients, Li T(1/2) during SPS was on average 48.9% shorter than without SPS. Furthermore, in one subject in whom urinary Li data were available, Li clearance with SPS was superior to Li renal clearance. Prolonged constipation was noted in one patient whereas mild hypokalemia was noted in six patients treated with SPS.
Conclusion: This study shows that SPS reduced Li T(1/2) and suggests that SPS is capable of promoting Li elimination in chronic intoxications. These results warrant a prospective trial looking at the use of SPS in the treatment of Li overdose as an adjunct to supportive measures and hemodialysis.