A multicenter study of a pill that combines two drugs for hypertension shows significant benefit for people with hard-to-control high blood pressure.
The study, conducted at the University of Maryland School of Medicine and 118 other sites, was focused on bringing down systolic blood pressure, the top number in a blood pressure reading, which is the more difficult number to bring down. The results of the study, called the INCLUSIVE trial, will be presented at the American Society for Hypertension conference in San Francisco on Tuesday, May 17, 2005.
"The percentage of patients whose blood pressure was controlled in this study was much higher compared to other combination therapy trials," says one of the study's two principal investigators, Elijah Saunders, M.D., professor of medicine at the University of Maryland School of Medicine and a cardiologist and hypertension expert at the University of Maryland Medical Center.
"This was the first large-scale hypertension study to include such a broad range of patient groups," says Dr. Saunders. "We found that this combination therapy reduced systolic blood pressure to a desirable level in 77 percent of the patients, and 83 percent of the patients in our study achieved an acceptable diastolic blood pressure. These results are significant," he adds.
The study began with a total of 1,005 participants with high blood pressure. A broad range of people participated in the study in terms of age and ethnicity. Half of them were women. All were given a diuretic alone for two weeks at the start of the trial. Nearly 30 percent of participants responded to this one drug, so they were eliminated from further participation. The remaining 736 people were given the combination pill of irbesartan (an angiotensin II receptor blocker) and a diuretic, hydrochlorothiazide, in increasingly stronger doses until their blood pressure reached a desirable goal. At the end of 18 weeks, the participants' systolic blood pressure (the top number) dropped an average of 21.5 points, from 154.4 to 132.9 points. Their diastolic blood pressure (the bottom number) fell an average of 10.4 points, from 91.3 to 80.9.
Current national guidelines recommend that blood pressure be kept below 140/90 millimeters of mercury for the general population, and less than 130/80 for people with diabetes or chronic kidney disease. Hypertension increases the risk of coronary heart disease, heart attack and stroke.
The study included at least 100 hypertensive patients in specific subgroups: those age 65 and older, African-Americans, Hispanic/Latinos, and people with type 2 diabetes. Patients with several risk factors for cardiovascular disease were also included, such as obesity, abnormal glucose tolerance, high triglycerides and low high-density lipoprotein, the so-called "good" cholesterol. According to Dr. Saunders, all of these subgroups represent a large part of the hypertensive population in the U.S. They may require two or more medicines to reach a desirable blood pressure goal.
Saunders says the medication was the only factor being tested in the study. There was no effort to adjust diet or exercise, which can also control blood pressure. "It is fair to say that this control was almost solely due to the drug therapy," Saunders says.
The patient subgroups in the study showed similar results. For example, in the older group of people age 65 and over, the mean systolic blood pressure at the start of the trial was 157. At the end of 10 weeks, average systolic blood pressure was down 14.9 points. At the conclusion of the study at week 18, after patients had received a higher dose of the combination medicine, their systolic readings had dropped an average of 23 points, to 134.
In the African-American subgroup, blood pressure dropped 20.7 points by the end of the study to an average systolic reading of 135.2.
The Hispanic/Latino subgroup had a drop in systolic blood pressure from an average of 154.5 to 131.8 by the end of the study. Patients with Type 2 diabetes showed an average drop of 18.2 points. The average systolic blood pressure of the women enrolled in the study dropped from 153.9 to 131.
"We believe this combination will be beneficial for many people who have not been able to bring their blood pressure under control," says Saunders, who adds that there is a great need for better therapies since only about one-third of people with hypertension are able to bring it under control.
The study was funded by the Bristol-Myers Squibb/Sanofi-Synthelabo Partnership. They are makers of Avalide®, the irbesartan-hydrochlorothiazide combination medicine used in the study.