The Pharmaceutical Journal
Vol 277 No 7427 p600
18 November 2006

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Oral vasopressin receptor antagonist improves serum sodium in hyponatraemia

Tolvaptan, an orally active vasopressin V₂-receptor antagonist, is an effective treatment of hyponatraemia, new research shows. The drug promotes aquaresis — excretion of electrolyte-free water.

Researchers examined the effects of tolvaptan in two trials involving 448 patients with hyponatraemia (serum sodium <135mmol/L) from various causes (eg, chronic heart failure and cirrhosis).

They found that within eight hours of administering treatment, patients’ serum sodium concentrations were significantly higher in those given tolvaptan than in those given placebo. More patients assigned to tolvaptan had normal serum sodium concentration on day four and day 30 than did patients assigned to placebo (P<0.001 for both). And when treatment was discontinued serum sodium concentrations reverted to levels similar to those seen in patients given placebo (New England Journal of Medicine 2006;355:2099).

The author of an accompanying editorial (ibid, p2146) suggests that future studies examine the potential of V_1A/V₂-receptor antagonists.