Although the median onset time of total antidepressant-induced hyponatremia/SIADH was shorter than that for antipsychotic-induced hyponatremia [53], despite normal levels of ADH, some psychotropic drugs (sertraline, haloperidol), antiepileptics (carbamazepine, lamotrigine), and chemotherapeutics (cyclophosphamide) increase vasopressin V2 receptor (V2R) mRNA and aquaporin-2 (AQP2) protein expression of the inner medullary collecting duct cells, increasing water absorption even at normal or low ADH levels and leading to nephrogenic syndrome of inappropriate antidiuresis (NSIAD) [54]. The gene discussed is AQP2; the disease is nephrogenic syndrome of inappropriate antidiuresis.