Utilizzo di tolvaptan in un caso di iponatriemia grave da SIADH in corso di meningite

Vaptans, vasopressin V2 receptor antagonists, are new drugs indicated in the treatment of Inappropriate ADH Secretion Syndrome (SIADH). We report a case of SIADH in a patient affected by AIDS. During a hospitalization for an ongoing CMV meningitis she developed a severe hyponatremia (114 mEq/L), which was initially treated with restriction of free water. When the diagnosis of SIADH was done (plasma Osmolarity 240 mOsm/kg, urinary sodium >30 mEq/24 h, normal volemia, lack of hypocorticosurrenalism and hypothyroidism), tolvaptan was given at the dose of 15 mg/day. Important fluctuations of plasma Na were observed thereafter (119-143 mEq/L). The progressive reduction of the drug (to 2 mg/die) allowed a stable correction of natremia. Unconsciousness determined the impossibility of the patient to freely access to water, thus explaining the fluctuations of natremia and the difficult management of the drug. Only a posology reduction to doses lower than those available for sale allowed a stable correction of natremia.