Absorption and Excretion of Furosemide-S35 in Human Subjects

Furosemide labeled with radioactive sulphur (S35) was given intravenously, intramuscularly or orally to adult subjects without any detectable cardiorenal disease. Peak plasma levels of radioactivity were found at 30 minutes and at 60 minutes after intramuscular and oral administration, respectively, of single doses. Approximately 80% of the dose given was recovered in the urine in 24 hours after intravenous or intramuscular injection of single doses. Following oral administration of single doses to 2 subjects, the 24-hour urinary recoveries were 26% and 54%, and fecal recovery was 2.1%. Comparison of rates of urinary excretion revealed that between 69% and 97% of the recovered activity was excreted in the first 4 hours after the drug was given, regardless of route of administration.