Lithium has been the first line drug in treating bipolar disorder. It has a low therapeutic index and toxic levels are frequently seen in clinical practice. Chronic lithium intoxication due to progressive accumulation of lithium was found to be more common. Symptoms are primarily neurologic; mental status is often altered and can progress to coma. The aim of the study is to evaluate the neurotoxicity among lithium intoxicated patients and its association with serum lithium levels through a cross sectional hospital based study over four years in the Poison Control Center, Ain Shams University Hospitals (PCC-ASUH). Factors affecting the outcome of lithium intoxicated patients were deduced.
Subjects and methods: Lithium intoxicated patients presented to the PCC-ASUH during the period from January 2011 to January 2015 were prospectively evaluated. For every patient we recorded the duration of lithium intake, comorbidities and concomitant use of medications. Clinical manifestations, serum lithium level, renal function (serum urea and creatinine) and serum electrolytes (sodium and potassium) in addition to the treatment characteristics were also recorded. Patients were divided according to their outcome into two groups: (Survivors and Non survivors).
Results: Twenty five lithium intoxicated patients were enrolled in our study; the mean duration of lithium therapy was similar in both groups (more than 12 years). The main clinical presenting sign of lithium intoxicated patients was coma with its different grades. Glasgow Coma Score (GCS) was significantly lower among non survivors.  Relevant history of diabetes mellitus and hypertension was found in 15 patients and 13 patients respectively. Non psychotropic medications (including angiotensin converting enzyme inhibitors and diuretics) that interact with lithium clearance were more prevalent among non survivors. Neuroleptics were used by 22 patients and this was of no significant difference between survivors and non survivors. There was no significant difference between serum lithium levels in survivors and non survivors. Rehydration therapy with intravenous fluids was significantly more prevalent among the survivors. While no significant difference was found between both groups as regards the use of hemodialysis.
Conclusion: The serious morbidity suffered by lithium intoxicated patients might be reduced by careful monitoring and awareness of factors that might predict their outcomes including altered conscious level or drug interactions (diuretics or angiotensin converting enzyme inhibitors). Clinicians should seriously maintain a high level of suspicion in treating patients maintained on lithium noting that serum lithium levels do not accurately predict toxicity and they should not solely rely on it.