The pharmacokinetics and pharmacodynamics of azosemide were evaluated after intravenous (IV) administration of the same total dose of azosemide, 1 mg kg 71 , in dierent infusion times, 1 min (treatment I) and 4 h (treatment II) to rabbits (n=5, each). The loss of water and electrolytes in urine induced by azosemide was immediately replaced with infusion of equal volume of lactated Ringer's solution. Some pharmacokinetic parameters of azosemide were dierent between treatments I and II. For example, the mean value of terminal half-life (70ยด5 versus 107 min), total body clearance (5ยด88 versus 8ยด32 mL min 71 kg 71 ), renal clearance (3ยด45 versus 6ยด51 mL min 71 kg 71 ), and mean residence time (18ยด5 versus 31ยด7 min) increased signiยฎcantly in treatment II. The 8 h urine output (236 versus 733 mL) and 8 h urinary excretion of sodium (29ยด2 versus 76ยด4 mmol) and chloride (27ยด5 versus 78ยด9 mmol) increased signiยฎcantly in treatment II although the total amount of 8 h urinary excretion of unchanged azosemide increased by only 15% in treatment II. This could be due to the fact that the urinary excretion rates of azosemide in treatment II remained for a longer period of time close to the maximally ecient urinary excretion rates of azosemide for both urine output and urinary excretion rates of sodium than in treatment I. Plasma concentrations of azosemide and hourly urine output and hourly urinary excretion of azosemide, sodium, potassium, and chloride during the apparent steady state (between 2 and 4 h) in treatment II were fairly constant.