Effects of Chlorothiazide on Systemic Hemodynamics in Essential Hypertension

Nineteen observations were made in 12 patients with early essential hypertension. The comparative effects upon mean arterial blood pressure, cardiac index, and total peripheral resistance of the acute and long-term administration of chlorothiazide were studied. With acute administration of the drug, a 10 per cent drop in mean arterial blood pressure, a decrease of 18 per cent in cardiac index, and an increase of 7 per cent in peripheral resistance were observed. With long-term administration, a decrease of 21 per cent in mean arterial blood pressure, an increase of 4 per cent in cardiac index, and a drop of 26 per cent in peripheral resistance were found. The conclusion is drawn that reduction of mean arterial blood pressure with acute administration of chlorothiazide is due to decrease in cardiac output, whereas with long-term use it is due to reduction in total peripheral resistance.