Rationale: Tolvaptan, an oral vasopressin V2 receptor antagonist, is a new approach for the treatment of adult patients with the syndrome of inappropriate antidiuresis (SIADH). However, dose-dependent side effect including rapid increase in serum sodium levels and liver injury, and the expensive price limit the long-term use of tolvaptan. We report a case of SIADH patient treated with intermittent lower dose of tolvaptan combined with fluid restriction.
Patient concerns: A 60-year-old woman presented of nausea and vomiting, dizzy and amaurosis, and transient disturbance, after a week of persistent diarrhea.
Diagnosis: Diagnosis of SIADH was based on severe persistent hyponatremia, decreased plasma osmolality, raised urinary sodium excretion, and the absence of other causes.
Interventions: She was given the treatment of tolvaptan 15 mg once daily, and experienced tolvaptan-related side effects including thirst and dry mouth, polyuria, and dizziness. Then, single dose of tolvaptan was reduced from 15 to 7.5 mg, and the interval between medication was gradually prolonged from 24 to 72 hours. Meanwhile, serum sodium was negatively correlated with the amount of daily water intake in interval days, so daily water intake of the patient was restricted to 1500 mL in interval days.
Outcomes: Serum sodium was maintained within the normal range, 137 to 141 mmol/L without liver damage.
Lessons: For patients with chronic SIADH, the tolvaptan dose should be individualized, and the regimen of intermittent lower dose of tolvaptan combined with fluid restriction maybe an effective choice.