Effect of Thiazide Diuretics on Plasma Volume, Body Electrolytes, and Excretion of Aldosterone in Hypertension

A study has been made at the Mayo Clinic of the results of treatment in 28 hypertensive patients receiving thiazide diuretics. The use of these agents produced a significant but very temporary reduction in plasma volume in most patients. The plasma volume reverted to or toward normal after the first week of treatment; therefore, hypovolemia could not explain the prolonged hypotensive effect of these drugs. Administration of thiazide diuretics did not deplete the body of its sodium stores, as measured by isotope studies in five patients on an unrestricted diet. Therapy with thiazides did not produce a persistent increase in urinary aldosterone excretion in the nine patients studied for this possibility.