Vasopressin-2-receptor antagonism augments water excretion without changes in renal hemodynamics or sodium and potassium excretion in human heart failure

Abstract

Diuretics are frequently required to treat fluid retention in patients with congestive heart failure (CHF). Unfortunately, they can lead to a decline in renal function, electrolyte depletion, and neurohumoral activation. Arginine vasopressin (AVP) promotes renal water reabsorption via the V2 receptor, and its levels are increased in CHF. This study was designed to assess the effects of a single oral dose of tolvaptan, a selective V2-receptor blocker, in the absence of other medications, on renal function in human CHF and to compare this to the effects of a single oral dose of furosemide. We hypothesized that V2-receptor antagonism would yield a diuresis comparable to furosemide but would not adversely affect renal hemodynamics, plasma electrolyte concentration, or neurohumoral activation in stable human CHF. Renal and neurohumoral effects of tolvaptan and furosemide were assessed in an open-label, randomized, placebo-controlled crossover study in 14 patients with NYHA II-III CHF. Patients received placebo or 30 mg of tolvaptan on day 1 and were crossed over to the other medication on day 3. On day 5, all subjects received 80 mg of furosemide. Tolvaptan and furosemide induced similar diuretic responses. Unlike tolvaptan, furosemide increased urinary sodium and potassium excretion and decreased renal blood flow. Tolvaptan, furosemide, and placebo did not differ with respect to mean arterial pressure, glomerular filtration rate, or serum sodium and potassium. We conclude that tolvaptan is an effective aquaretic with no adverse effects on renal hemodynamics or serum electrolytes in patients with mild to moderate heart failure.

Fig. 1

Chemical structure of tolvaptan. The chloride on the 7 position of the benzazepine and the methyl group on the 2 position of the aminobenzoyl moiety give tolvaptan good oral availability (14).

Fig. 2

Effect of tolvaptan, placebo, and furosemide on urine flow (U_VolR; A), urinary sodium excretion (U_NaV; B), urinary potassium excretion (U_KV; C), urine osmolality (U-Osm; D), renal blood flow (RBF; E), and glomerular filtration rate (GFR; F). Bars represent weighted averages ± SE over an observation period of 9 h. *P < 0.05.

Fig. 3

Changes in serum sodium concentration from baseline. Thick line, tolvaptan; dashed line, placebo; thin line, furosemide.

Fig. 4

Changes in serum potassium concentration from baseline. Thick line, tolvaptan; dashed line, placebo; thin line, furosemide.