Kinetics of urinary furosemide elimination in infants.

Using a one-compartment model, the urinary elimination kinetics of a single intravenous 1 mg/kg dose of furosemide (F) was studied in 13 infants, 9 days to 12 months old (mean 3.7 +/- (SD) 3.48 months old), and 1, 23-month-old child, with bilateral multifocal pneumonia, recovering from respiratory and cardiac insufficiency accompanying pneumonia and/or other diseases. F elimination half-life was determined with the use of a noninvasive method based on the drug's urinary excretion data. The drug urinary elimination t1/2 in the infants ranged from 0.654 to 3.29 h. Cumulative excretion of F in the infants' urine was similar to the values in healthy adults. Since the furosemide urinary half-lives found in infants were similar to the data reported in older children and healthy adults it is suggested that immaturity of renal function during the 1st year of life, i.e. in older infants, has no evident on the elimination kinetics of a 1 mg/kg intravenous dose of F. Mean F urinary elimination t1/2 in infants with pneumonia and cardiac insufficiency was significantly longer compared with the Ft1/2 found in children with the pneumonia alone (2.15 vs. 1.01 h, respectively), suggesting slower elimination of the drug in these patients.