Effects of tolvaptan on systemic and renal hemodynamic function in dogs with congestive heart failure

We investigated the effects of tolvaptan, a vasopressin V(2)-receptor antagonist, on diuretic response and systemic and renal hemodynamic characteristics in conscious dogs with congestive heart failure (CHF). We also compared these effects with those of furosemide, a loop diuretic.

CHF was induced by rapid right-ventricular pacing at 260 beats/min for at least 3 weeks, and maintained with a pacing rate of 220-240 beats/min. CHF dogs were orally given tolvaptan (10 mg/kg), furosemide (10 mg/kg) and vehicle in random order during the stable CHF state. Urine excretion, systemic and renal hemodynamic parameters, and plasma hormone levels were measured over 6-hour periods after drug administration.

Tolvaptan induced aquaresis with an increase in free water clearance, resulting in a significant increase in serum sodium concentrations and a decrease in cumulative water balance. Tolvaptan also decreased pulmonary capillary wedge pressure without affecting systemic vascular resistance, glomerular filtration rate or renal blood flow. Tolvaptan tended to increase plasma arginine vasopressin concentrations but did not affect plasma renin activity. In contrast, furosemide induced clear saluresis with increased electrolyte excretion, resulting in decreased pulmonary capillary wedge pressure. However, furosemide also decreased serum potassium concentration and increased plasma arginine vasopressin concentrations and plasma renin activity.

Tolvaptan elicited a potent aquaretic response and reduced the cardiac preload without unfavorable effects on systemic or renal hemodynamics, the renin-angiotensin-aldosterone system, or the sympathetic nervous system in CHF dogs. Thus, tolvaptan may offer a novel approach to remove excess water congestion from patients with CHF.