Indapamide versus hydrochlorothiazide in essential hypertension: measurement of peripheral resistance using plethysmography

Abstract

Seventeen patients (11 males and 6 females), aged 34 to 66 years, with uncomplicated essential hypertension completed a randomized, placebo-controlled, double-blind crossover study comparing indapamide (2.5 mg per day) with hydrochlorothiazide (50 mg per day).

The lead-in placebo period of 2 months was followed by two active drug phases, each of 3-months’ duration separated by a 2-month placebo washout period. The mean (±S.D.) standing systolic/diastolic blood pressures during placebo were 150±18/96±6 mmHg. During indapamide treatment the blood pressures were 137±16/90±7 mmHg and during hydrochlorothiazide 137±17/91±7 mmHg. Both drugs, therefore, reduced the systolic, diastolic and mean arterial blood pressures equally. Orthostatic changes in mean blood pressure and heart rate were similar with the two drugs. Both drugs lowered serum potassium (-14.3% with indapamide, -13.7% with hydrochlorothiazide) and increased serum uric acid (+26.7% with indapamide, +25.7% with hydrochlorothiazide) and cholesterol (+11.7% with indapamide, +11.1% with hydrochlorothiazide) equally.

Forearm blood flow and venous compliance were measured by a plethysmographic technique in 6 of the patients. Forearm blood flow of 3.53±0.58 ml/min/ 100 ml forearm volume during placebo was increased to 4.01±074 ml/min/100 ml during indapamide treatment and reduced to 3.40±1.16 ml/min/100 ml during the hydrochlorothiazide period, but the sample size did not permit detection of any significant differences. Venous compliance was not altered from baseline by the drugs.

No side-effects attributable to either of the two drugs were reported. It is concluded that in this study indapamide did not differ from hydrochlorothiazide in its effects on blood pressure, heart rate, venous compliance or biochemistry. It is suggested that a possible peripheral arteriolar vasodilator effect of indapamide should be further investigated.