Lactulose-associated lithium toxicity: a case series.

BACKGROUND: Lactulose is commonly used for constipation and hepatic encephalopathy. Its adverse effects of dehydration and serum electrolyte imbalances are widely known. OBJECTIVE: This study aimed to describe a case series of 3 patients receiving lactulose who developed lithium toxicity. METHODS: The authors described a case series of 3 patients admitted to a large county psychiatric hospital who developed lithium toxicity while taking lactulose for constipation or hyperammonemia. RESULTS: In all 3 cases of lithium toxicity, the patients were prescribed with lithium for acute mania and lactulose for constipation or hyperammonemia. One case required the patient to be transferred to a local emergency department for further treatment. CONCLUSIONS: This case series shows the interaction between lithium and lactulose. It is postulated that lactulose's effects of volume depletion can lead to poor renal excretion of lithium.