THE EFFECTS OF DIURESIS ON THE PHARMACOKINETICS OF THE LOOP DIURETICSFUROSEMIDE 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 ove rload. SUBJECTS AND METHODS: We studied 44 patients with New York Hear t Association class III or IV heart failure, ejection fraction less th an or equal to 40%, and an estimated excess fluid body weight greater than or equal to 6.8 kg. Oral furosemide or torsemide was administered before and after diuresis. Pharmacokinetic parameters were assessed b efore and after diuresis. RESULTS: Following diuresis, maximum plasma concentration increased from 11.0 +/- 5.0 mu g/mL to 13.9 +/- 6.8 with torsemide (P <0.05) and from 3.1 +/- 1.5 to 3.9 +/- 1.9 with furosemi de (P = 0.16). Maximum concentration increased by more than 30% in onl y one third of the patients. Total absorption (by area under the curve method) increased 6% among patients on torsemide (P = 0.38) and 7% am ong patients on furosemide (P = 0.63) and increased >30% in only 1 tor semide and 2 furosemide patients. The time to maximum concentration de creased from 1.40 +/- .82 h to 0.81 +/- 0.36 with torsemide (P <0.01). There were no differences between furosemide and torsemide in the eff ects of edema on absorption.CONCLUSION: Marked diuresis altered the ph armacokinetics of both furosemide and torsemide in only a small percen tage of patients. The use of adequate doses of oral diuretics in edema tous patients may be successful, thereby permitting home treatment wit h oral diuretics and avoiding the cost of hospitalizations or home int ravenous administration services. (C) 1998 by Excerpta Medica, Inc.