Vaptans: a novel class of drugs causing free water diuresis

We read with interest the recent review on diuretics. ¹ The author comprehensively discussed types of diuretics, their physiological basis and their clinical use as well as side-effects associated with them. We would also wish to mention vaptans, which have recently been incorporated in the management of hyponatremia. Vaptans are competitive antagonists of vasopressin receptors without detectable agonist activity. The various types of vaptans are mozavaptan, conivaptan, tolvaptan, satavaptan and lixivaptan. Their specificity for the various vasopressin receptors (V_1A, V_1B and V₂) differs between the various types. ²

The vaptans result in a water diuresis (aquaresis) that, if not offset by increased fluid intake, reduces body water content and raises plasma sodium concentration. These drugs are helpful in the treatment of hypervolaemic hyponatraemia associated with severe congestive heart failure or chronic liver failure, where the only other treatments currently available (i.e. fluid restriction and conventional diuretics) are slow-acting and less effective. Vaptans have also been successfully used in the management of the syndrome of inappropriate antidiuretic hormone (SIADH) secretion, a common cause of euvolaemic hyponatraemia. The most important contraindication to vaptan use is hypovolaemic hyponatraemia. Thus, before vaptans are used hypovolaemia needs to be ruled out clinically as well as with other laboratory investigations. ³

Declaration of conflicting interest

None.