Objective: Hypertension is the leading cause of morbidity and mortality, and blood pressure (BP) control is shown to reduce the risk of cardiovascular events. The present study aimed to investigate the efficacy and safety of chlorthalidone and hydrochlorothiazide for reducing systolic and diastolic BP in patients with mild-to-moderate hypertension.

Materials and Methods: The present study was a randomized clinical trial. Patients 18 years or older with mild-to-moderate hypertension with or without prior antihypertensive medications were enrolled. Patients were randomly assigned to the chlorthalidone or hydrochlorothiazide group. The dose of study medication could be up-titrated at the 6-week. The primary outcomes were the reduction in systolic and diastolic BP, the rate of office BP control at 12 weeks, and the rate of adverse events.

Results: Fifty-six patients (mean age of 49.8±11.1 years) and 42.9% male, were included. Forty-three patients (76.8%) had known hypertension. Mean sitting office systolic BP (SBP) and diastolic BP (DBP) at baseline was 153.2±9.6 and 91.8±9.2 mmHg, respectively. The average daily dose of chlorthalidone and hydrochlorothiazide was 16.1±5.8 and 32.4±11.6 mg. The mean reduction in SBP in the chlorthalidone and hydrochlorothiazide groups was 28.7±12.2 and 22.8±13.7 mmHg (p=0.118), and DBP was 14.4±7.5 and 9.1±6.6 mmHg (p=0.011), respectively. The rate of office BP control was significantly greater in the chlorthalidone group at 91.7% versus 61.5% (p=0.013). There was no significant difference in the rate of adverse events between the groups.

Conclusion: Chlorthalidone was shown to be more effective than hydrochlorothiazide for office BP control. There was no difference in adverse events.