Water diuresis from clonidine (catapres).

The renal hemodynamic and excretory effects of clonidine were tested in two groups of dogs. In one group, the drug was given directly into the renal artery at a rate of 1.2 mug/min and resulted in a significant decrease of the effective renal plasma flow (ERPF) in both kidneys, an increase in filtration fraction (FF), urine volume (UV), and free water clearance (CH2O) and had no effect upon the glomerular filtration rate (GFR), osmolar clearance (Cosm) and the excretion of sodium (UNaV), chloride (UC1V), potassium (UKV), calcium (UCaV) and phosphorous (UPO4V). No unilateral effect was appreciated. In the second group of animals it was given intravenously at a rate of 12.0 mug/min and resulted in a significant decrease of ERPF, UNaV, UC1V, and increase in FF, UV, and CH2O) but had no effect upon GFR, Cosm, UKV, UCaV and UPO4V. Systemically it decreased heart rate (H.R.) and respiratory rate (R.R.) in both groups of animals; it increased blood pressure (BP) in Group 1 and had no effect on BP in Group 2.