The Effects of Diuresis on the Pharmacokinetics of the Loop Diuretics Furosemide and Torsemide in Patients with Heart Failure

Purpose: To evaluate the pharmacokinetics of furosemide and torsemide before and after diuresis in patients presenting with marked fluid overload. Subjects and Methods: We studied 44 patients with New York Heart Association class III or IV heart failure, ejection fraction ≤40%, and an estimated excess fluid body weight ≥6.8 kg. Oral furosemide or torsemide was administered before and after diuresis. Pharmacokinetic parameters were assessed before and after diuresis. Results: Following diuresis, maximum plasma concentration increased from 11.0 ± 5.0 μg/mL to 13.9 ± 6.8 with torsemide ( P 30% in only 1 torsemide and 2 furosemide patients. The time to maximum concentration decreased from 1.40 ± .82 h to 0.81 ± 0.36 with torsemide ( P