Commentary

Lithium toxicity in a patient with bipolar disorder: Lessons learned

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A detailed family history later confirmed a strong family history of renal disease: her mother had lupus nephritis with nephrotic syndrome, and her brother had died from complications of a rapidly progressive glomerulonephritis. Her renal function prior to lithium initiation was within normal limits (urea: 4.0 mmol/L; serum creatinine: 78 µmol/L).

In the ward, lithium and aripiprazole were discontinued, and she was hydrated. Combined care with the psychiatric and medical teams was established early to safeguard against potential CNS deterioration. She showed marked clinical improvement by Day 3, with the resolution of coarse tremor and rigidity as well as normalization of blood parameters. Her lithium level returned to a therapeutic level by Day 4 after lithium discontinuation, and her renal profile gradually normalized. She was restarted on aripiprazole 10 mg/d for her bipolar illness and responded well. She was discharged on Day 5 with a referral to the nephrology team for further intervention.

Lessons learned

This case highlights the issue of lithium safety in susceptible individuals and the importance of risk stratification in this group of patients. Lithium is an effective treatment for bipolar I disorder and has also been used as adjunctive treatment for major depressive disorder, schizoaffective disorder, treatment-resistant schizophrenia, anorexia nervosa and bulimia nervosa, and the control of chronic aggression.9 Lithium is completely absorbed by the gastrointestinal tract following ingestion, is not metabolized, and is eliminated almost entirely by the kidneys (though trace amounts may be found in feces and perspiration).

In our case, a detailed family history of renal disease was not adequately explored until our patient presented with signs suggestive of lithium toxicity. Our patient had been prescribed lithium 600 mg/d as a maintenance therapy. Upon starting lithium, her baseline biochemical parameters were within normal limits, and renal issues were not suspected. The hair thinning and hair loss she experienced could have been an adverse effect of valproate sodium or a manifestation of an underlying autoimmune disease. Coupled with the use of NSAIDs that could have precipitated acute kidney injury, her poor oral intake and dehydration during the acute illness further impaired lithium excretion, leading to a suprathreshold plasma level despite a low dose of lithium. Therefore, before prescribing lithium, a thorough medical and family history is needed, supplemented by an evaluation of renal function, serum electrolytes, and thyroid function to determine the starting dosage of lithium. Routine vital sign assessment and ECG should also be conducted, and concurrent medications and pregnancy status should be confirmed before prescribing lithium. Regular lithium level monitoring is essential.

Measuring a patient’s estimated glomerular filtration rate (eGFR) is recommended to validate renal status10 and classify and stage kidney disease.11 Combining eGFR with blood urea nitrogen, serum creatinine, and urine microscopic analysis further improves the prediction of renal disease in early stages. We recommend considering a blood test for autoimmune markers in patients with clinical suspicion of autoimmune disease, in the presence of suggestive signs and symptoms, and/or in patients with a positive family history (Table).

Initiating lithium: A checklist

Before starting lithium, in addition to conducting a detailed clinical evaluation, information about symptoms and the risk of lithium toxicity should be discussed with patients.12 Our case serves as a timely reminder that the lack of suggestive biochemical parameters of renal disease should not rule out an underlying renal disease, and a strong family history of renal disease should warrant suspicion of a possible autoimmune origin.

We suggest that future studies evaluate the risks of lithium toxicity in susceptible groups of patients, such as those with family history of renal disease.

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