Lithium chronic and acute-on-chronic poisoning: A retrospective case series

Objective: Lithium is a first line drug for treatment and prevention of bipolar disorder and it is effective in reducing relapse and the risk of suicide. Chronic lithium treatment is often associated with toxicity since the drug commonly induces nephrogenic diabetes insipidus or interstitial nephritis, due to its action on tubular renal function. This condition can lead to progressive lithium accumulation followed by lithium-induced adverse reactions.1 The aim of this study was to retrospectively evaluate the patients admitted to Florence Toxicology Unit in the last twenty years (1994-2014) for lithium intoxication. The age, dose ingested and plasma lithium concentration at admission were evaluated. Renal impairment, neurological symptoms, and average length of stay (days, ALOS) in hospital were also investigated. Case series: In total 71 patients were included in the study. Chronic progressive lithium accumulation due to renal or gastrointestinal dysfunction and to circulating volume decrease occurred in 29 out of 71 patients (41%). All cases (100%) presented with neurological symptoms (agitation, mental confusion, tremors, hyperreflexia), while renal impairment was present in 19 out of 29 (65%) patients. Furthermore, magnetic resonance imaging (MRI) or positron emission tomography (PET) documented brain neurodegeneration in 7 cases (24%) leading to an irreversible lithium-neurotoxic syndrome.2 In this group the ALOS was 8.5 days. In addition, suicide attempts in patients on chronic lithium therapy occurred in 42 out of 71 patients (59%) and neurological symptoms and renal impairment were present in 2 (4%) and 2 (4%) patients, respectively. In this group the ALOS was 3.5 days. Conclusion: Lithium toxicity is more severe in patients with chronic progressive lithium accumulation compared to acute lithium poisoning for suicide attempt in patients on chronic lithium therapy as documented by the ALOS. Indeed, intracellular lithium accumulation poses a substantial risk for neurological symptoms, renal impairment and brain neurodegeneration. Lithium plasma concentration and renal function should be closely monitored3 in order to obtain a prompt diagnosis and limit brain damage.