Chronopharmacology of trichlormethiazide in rats

Trichlormethiazide was given orally at 1200 hrs or 2400 hrs to rats. Its diuretic effects were greater at 1200 hrs than at 2400 hrs. There were significant correlations between urinary trichlormethiazide and its effects in both trials. The regression lines of two trials did differ. These findings indicate that the effects of trichlormethiazide vary with its administration time. Time-dependent variations in urinary trichlormethiazide and susceptibility to the agent might be involved in this phenomenon.