Torasemide is an effective diuretic in the newborn rabbit

The effect of intravenous (i.v.) torasemide an diuresis and renal function was evaluated in three groups of normoxemic, 5- to 10-day-old, newborn New Zealand White rabbits. The animals of group 1 received 0.2 mg/kg of torasem ide i.v., whereas in group 2 an i.v. dose of 1.0 mg/kg was given. The third group of animals received a bolus i.v. dose of 1.0 mg/kg torasemide with c ontinuous i.v. replacement of estimated urinary fluid and electrolyte losse s. Torasemide proved to be an effective, potassium-sparing diuretic, withou t significant effect on glomerular filtration rate (GFR). Renal blood flow (RBF) fell and the renal vascular resistance (RVR) rose in all three groups of animals, although the rise in RVR in group 3 was not significant. These changes in renal hemodynamics were most pronounced in the animals of group 2 and are probably secondary to torasemide-induced hypovolemia (2.8% loss of body weight) and accompanying humoral reactions, such as an increase in angiotensin II (not measured). When the latter is pre vented by simultaneou s re-infusion of an electrolyte solution (group 3), replacing urinary losse s, GFR increases and the changes in RBF and RVR are blunted. We conclude th at torasemide is an effective, potassium-sparing diuretic in newborn rabbit s. No evidence was found for a vasodilatory action of the drug.