Because of its diuretic and antihypertensive actions, chlorothiazide has been recommended for use in edematous and hypertensive states,1-10 including renal disease.11-13 Although chlorothiazide is known to cause increased excretion of Na and K,14-21 only few untoward clinical reactions have been described during its use.22-26 However, since patients with renal insufficiency may have a diminished ability to conserve Na, K, and Cl ions, the administration of such a diuretic might accentuate the process of depletion. We present two cases of chronic glomerulonephritis to emphasize the dangers in the use of chlorothiazide in patients with renal insufficiency. In each case electrolyte balance studies were carried out, including the measurement of total exchangeable Na and K by the isotope dilution principle.
Serum and urine Na and K were determined by flame photometry. Osmolality of serum and urine was measured by the method of freezing point depression using the Fiske Osmometer. Na22 and K42