RESUMO
Lithium salts (lithium) is a psychotropic drug widely used as a pharmacological option in managing bipolar disorder. Regular monitoring of serum levels is necessary due to the narrow therapeutic range of lithium. Typically, the diagnosis of lithium intoxication is based on the presence of elevated plasma levels. Nevertheless, poisoning can ensue from either acute ingestion or chronic use, even in patients with normal plasma levels. The utilization of lithium has been decreasing due to its potential for multiorgan toxicity. Lithium accumulation in renal distal tubular cells is a prevalent cause of acquired arginine vasopressin resistance (AVP-R), previously known as nephrogenic diabetes insipidus (DI). Some patients might also experience neurologic persistent symptoms after plasma level normalization, a condition known as the syndrome of irreversible lithium-effectuated neurotoxicity (SILENT). We present a case report of acquired AVP-R following prolonged lithium use. This case report aims to increase awareness, particularly among those who may be unfamiliar with the use of lithium and its associated adverse reactions. In addition, it seeks to highlight the dissociation between clinical manifestations and lithium plasma levels, emphasizing the need for careful evaluation in patients receiving lithium treatment.