Saluretic effect of the loop diuretic torasemide in chronic renal failure. Interdependence of electrolyte excretion

The effects of torasemide have been studied in 7 healthy controls and 9 patients with stable chronic renal failure of various degrees. After a control period of 3 days torasemide 20 mg i.v. caused a dramatic increase in diuresis and electrolyte excretion without affecting the glomerular filtration rate. The duration of action of torasemide, tau, averaged 6 h and was independent of the creatinine clearance, CLCR. When related to tau the drug-induced excretion of Cl-, Na+, K+, Ca2+ and Mg2+ showed strong linear dependence on CLCR. Both the kaliuresis and the calciuresis during tau were tightly correlated with the natriuresis over the broad range of CLCR. Similarly, the excretion of Mg2+ was dependent on the kaliuresis. The torasemide-induced kaliuresis amounted to 12% of natriuresis, as after furosemide. The kaliuretic effect of loop diuretics is smaller than that of the thiazides. After tau, e.g. over a 24 h period, kaliuresis was not correlated with natriuresis. The magnitude of the rebound effect was diminished with increasing renal impairment.