Irbesartan monotherapy in systemic hypertension: An open-label, uncontrolled trial

Background: Irbesartan is an orally active, specific blocker of the AT₁ receptor of angiotensin II that produces insurmountable antagonism. Irbesartan's plasma half-life of 11 to 15 hours and higher affinity for the AT₁ receptor versus other angiotensin II receptor subtypes may make it a suitable choice for once-daily treatment of hypertension. Few studies have examined the efficacy of this agent in Asian patients.Objective: The purpose of this open-label, uncontrolled study was to assess the 24-hour efficacy of irbesartan once-daily monotherapy in Chinese outpatients with mild to moderate hypertension.Methods: Patients with stage I or stage II hypertension (as defined by the Sixth Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure) were treated with irbesartan once daily for 6 to 8 weeks. The dose of irbesartan was titrated from an initial dose of 150 mg to 275 mg or 300 mg if adequate blood pressure (BP) control was not achieved by week 3 or 4; doses were taken once daily between 8 am and 9 am. For each patient, 24-hour ambulatory BP monitoring was performed twice, once before and once after 6 to 8 weeks of treatment.Results: A total of 25 patients (mean age, 54 years) were enrolled; 24 completed the study. Mean 24-hour systolic/diastolic BP after irbesartan treatment was significantly decreased compared with baseline values (128 ± 14 mm Hg/82 ± 8 mm Hg vs 143 ± 12 mm Hg/91 ± 7 mm Hg, P < 0.05 for both). The mean final dose of irbesartan was 243.8 ± 63.5 mg daily after a 7-week titration period. Mean daytime (6 am to 6 pm) BP decreased from 146 ± 11 mm Hg/94 ± 7 mm Hg to 130 ± 14 mm Hg/84 ± 8 mm Hg (P < 0.05), and nighttime (6 pm to 6 am) BP decreased from 139 ± 14 mm Hg/88 ± 7 mm Hg to 127 ± 15 mm Hg/81 ± 9 mm Hg (P < 0.05). The BP decrease was more pronounced during the day. Before treatment, the circadian variation showed a peak BP at 11 am and a nadir at 4 am. After treatment, significant BP reductions versus baseline (P < 0.05 for both diastolic and systolic BP) were observed for 23 of the 24 hourly mean points. The circadian rhythm of BP cycles was preserved. Mean heart rate did not change after treatment. Two patients reported dizziness and 1 reported heartburn.Conclusions: Irbesartan administered as once-daily monotherapy provided effective BP control during 23 of the 24 hourly mean points while preserving the circadian rhythm of BP cycles, and was well tolerated.