Comparative Efficacy of Irbesartan/

Objective: To compare blood pressure (BP) control in patients receiving irbesartan/hydrochlorothiazide (HCTZ) and valsartan/HCTZ at a tertiary care university hospital in Oman. Subjects and Methods: This was a retrospective observational study, where 232 patients’ medical records were reviewed during a 3-month period, July to September 2010, at Sultan Qaboos University Hospital in Oman. BP readings of the previous 6 months were also retrieved from the electronic medical records. Analyses were conducted using univariate statistical techniques. Results: The mean age of the cohort was 58 8 11 years (range: 21–88). Sixty-nine (30%) patients were on the irbesartan/HCTZ combination (150/12.5 mg) and 163 (70%) were on the valsartan/HCTZ combination. The patients on the valsartan/HCTZ combination were divided into two subgroups: 117 (72%) received 160/12.5 mg and 46 (28%) 80/12.5 mg. Diabetic patients (43/69, 62%, vs. 61/163, 37%, p ! 0.001) and those with diabetic nephropathy (8/69, 12%, vs. 7/163, 4%, p = 0.039) were prescribed more often irbesartan/HCTZ than valsartan/HCTZ. In comparison to the valsartan/HCTZ cohort, the irbesartan/HCTZ group Received: April 10, 2012 Accepted: October 24, 2012 Published online: December 12, 2012 K.A. Al Balushi, PhD Department of Pharmacology and Clinical Pharmacy College of Medicine and Health Sciences, Sultan Qaboos University PO Box 35, Al-Khod 123 (Sultanate of Oman) E-Mail kal_balushi @ hotmail.com © 2012 S. Karger AG, Basel 1011–7571/13/0223–0265$38.00/0 Th is is an Open Access article licensed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs 3.0 License (www.karger.com/OA-license), applicable to the online version of the article only. Distribution for non-commercial purposes only. Al Balushi /Habib /Al-Zakwani Med Princ Pract 2013;22:265–269 DOI: 10.1159/000345389 266 hypertension by targeting different aspects of its pathophysiology. Some of the drugs are used as monotherapy while others are used in combination. It is estimated that more than two thirds of hypertensive subjects are not controlled on one drug alone and will thus require two or more antihypertensive agents selected from different drug classes to provide optimum control [4] . Angiotensin II receptor blockers (ARBs) are an effective antihypertensive option with renal and cardioprotective effects coupled with lower adverse effect profile [5] . ARBs differ in pharmacodynamic and pharmacokinetic properties, which may translate into significant differences in their relative antihypertensive potency. ARBs are also available in fixed-dose combination with other antihypertensive drugs such as thiazide diuretics and calcium channel blockers. Valsartan is a potent ARB that has a good BP-lowering effect at doses of 80–320 mg [6] . It is also indicated for heart failure and postmyocardial infarction to reduce cardiovascular mortality [7] . Irbesartan is another ARB prescribed at doses from 75 to 300 mg. It is also approved for the treatment of hypertension. In some countries, irbesartan has been approved for the treatment of nephropathy in patients with hypertension and type 2 diabetes mellitus [8, 9] . There are currently only a few published studies [10, 11] on the comparison of irbesartan/hydrochlorothiazide (HCTZ) and valsartan/ HCTZ combinations with respect to BP control. Therefore, the aim of this study was to compare the effectiveness of irbesartan/HCTZ and valsartan/HCTZ with respect to BP in patients with mild to moderate hypertension at Sultan Qaboos University Hospital, in Muscat, Oman. Subjects and Methods This was a retrospective observational study where the electronic medical records of 232 adult patients ( 6 18 years) who were prescribed irbesartan/HCTZ or valsartan/HCTZ and diagnosed with mild to moderate hypertension were reviewed in a 3-month period between July and September, 2010. The study took place at Sultan Qaboos University Hospital, which is a nearly 600-bed tertiary-care university hospital in Muscat, Oman. Each patient’s BP readings were retrieved from the medical records for the previous 6 months prior to the index date. Patients were excluded if they did not have a diagnosis of mild to moderate hypertension. Furthermore, they also had to contribute at least two BP readings (one reading in the index period, July to September 2010, and the other BP reading in the preindex 6-month period). Patients were also excluded if they were not on the two study medications throughout the study period. Arterial BP was measured by a trained nurse using an oscillometric automatic BP monitor and by a physician using a calibrated standard sphygmomanometer of the appropriate cuff size. All BP measurements were taken after the patient had rested in a sitting position for 5 min. Apart from the BP readings, the study also captured the following variables: age, weight, height, gender (male, female), nationality (Omani, non-Omani), other comorbidities (diabetes mellitus, dyslipidemia, ischemic heart disease, congestive heart failure, stroke, myocardial infarction, atrial fibrillation, anemia, obesity, diabetic nephropathy, diabetic retinopathy, and deep vein thrombosis), and other antihypertensive medications. Ethical approval for the study was obtained from the Ethics Review Committee of the College of Medicine and Health Sciences, Sultan Qaboos University, Muscat, Oman. The study was part of an MSc project for the second author (J.Q.), who did all the data collection while analyses were shared between all the authors. Power Analysis At least 6 months’ follow-up on 177 patients were needed (118 on the valsartan group and 59 on the irbesartan group; 1:1⁄2 ratio, based on prevalence of prescribing) to have 80% power to detect a difference of 10 mm Hg of BP difference (systolic or diastolic) between the two cohorts at the 5% alpha (significance) level. Because of missing data, additional data were retrieved for 55 subjects for a total of 232 (study sample). Statistical Analysis Descriptive statistics were used to describe the data. For categorical variables, frequencies and percentages were reported. Differences between groups were analyzed using Pearson’s  2 tests (or Fisher’s exact tests for cells less than 5). For continuous variables, mean and standard deviation were used to present the data while analysis was performed using Student’s t test or paired t test, wherever appropriate. An a priori two-tailed level of significance was set at the 0.05 level. Statistical analyses were conducted using STATA version 12.1 (STATA Corp., College Station, Tex., USA).