Chronopharmacological study of furosemide; (IV). Examination in aged rats

We have previously reported that a time-dependent variability is observed in the diuretic effects of furosemide in young Wistar rats. The present study was undertaken to examine the influence of ageing on chronopharmacological profiles of furosemide in rats. Furosemide (5 mg/kg) was injected intra-arterially in young (10-11 week old) and aged (21-22 month old) Wistar rats at 1000 hrs or at 2200 hrs. Urine was collected for 60 min after the drug and urinary excretion of sodium and furosemide were determined respectively. Urine volume and urinary excretion of sodium and furosemide following the drug injection were significantly greater at 1000 hrs than at 2200 hrs in the young rats as observed in the previous study. However these administration time-dependent changes in the effects of furosemide and its urinary amount disappeared in the aged rats. These findings indicate that the mode of the time-dependent changes in the effects of furosemide is altered in aged Wistar rats.