Differences in the duration of diuretic effects and impact on the renin-angiotensin-aldosterone system of furosemide in healthy dogs.

Our aim was to investigate the differences in the duration of diuretic effects and impact on the renin-angiotensin-aldosterone (RAA) system of furosemide as a model of short- and long-acting loop diuretics. Anesthetized dogs (n=6) were randomized into placebo, intravenous bolus administration (IB) and chronic rate infusion (CRI) groups. This study was conducted with a crossover study. Furosemide (4 mg/kg) was diluted to 18 mL in sterile saline. Furosemide was infused at 0.5 mg/kg/hr for 8 hr in the CRI group or was injected at 0 and 4 hr (both 2 mg/kg) in the IB group. Blood and urine samples were collected at baseline and at 1, 2, 4, 5, 6 and 8 hr. Compared with the baseline, the IB group had a significantly increased urine output at 1 and 5 hr. The CRI group had a significantly increased urine output persisting for 4 hr compared with the baseline. Compared with the placebo group, 8-hr urine output and 8-hr sodium excretion were significantly increased in the IB and CRI groups; the values in the CRI group were significantly higher than those in the IB group. Eight-hour potassium excretion was significantly increased in the IB and CRI groups. The plasma aldosterone concentration was significantly elevated in the IB group at 8 hr. Duration of action may be a predominant cause of loop diuretic-related differences. Persistent diuresis may cause greater diuretic effects than transient diuresis, with less elevation of the plasma aldosterone concentration.