Study Stopped Early: High Blood Pressure Drug Less Effective than Diuretic

March 9, 2000

The National Heart, Lung, and Blood Institute (NHLBI) has stopped part of a large clinical trial of blood pressure medications because doxazosin (sold under the name Cardura®), one of the drugs, wasn''t as effective as a less expensive diuretic medication.

"Cardura was less effective at lowering blood pressure and at preventing cardiovascular complications, particularly heart failure," said Curt Furberg, M.D., Ph.D., of Wake Forest University Baptist Medical Center, chairman of the study''s steering committee. "It is also ten times more expensive than the diuretic."

The study, known as ALLHAT for Antihypertensive and Lipid Lowering Treatment to Prevent Heart Attack, was designed to compare a diuretic, the traditional therapy for lowering blood pressure, with three newer drugs for controlling hypertension. The study''s goal is to determine which treatment is most effective at reducing heart attacks, strokes and other complications of uncontrolled hypertension.

The approximately 9,000 study participants who took Cardura had 25 percent more serious complications from hypertension than the group taking the diuretic chlorthalidone. The participants in the Cardura group were also twice as likely to develop or be hospitalized for congestive heart failure. The study has more than 42,000 participants at 623 clinical sites in the United States, Puerto Rico, the Virgin Islands and Canada.

Cardura is an alpha blocker, a type of hypertension drug that works by dilating the blood vessels. More than 1 million people nationwide take Cardura and other alpha blockers (Hytrin or Minipres) to lower blood pressure.

"The recommendations from ALLHAT to physicians is not to use alpha blockers as a first-line therapy," said Furberg. "Our advice to the public is to consult with your physician if you''re taking an alpha blocker for hypertension."

The 9,000 participants in the study who were taking Cardura are being offered an alternative medication.

"Patients on an alpha blocker should see their doctors and not just stop taking it," said Dr. Jeffrey Cutler, director of the NHLBI Clinical Application and Prevention Program. "We cannot conclude that the drug was harmful. Rather it didn''t work as well as the diuretic in reducing cardiovascular disease."

ALLHAT is the largest study ever to compare different types of hypertension drugs. In addition to Cardura, it is looking at amlodipine (sold under the name Norvasc) and lisinopril (sold under the names Prinivil and Zestril). Only the Cardura portion of the study will stop. The remainder of ALLHAT will continue until its scheduled end in 2002.

"ALLHAT is important to clinicians who treat patients with high blood pressure because it compares newer, often insufficiently tested drugs against a regular diuretic, an inexpensive class of drugs with well documented benefits," said Furberg.

In addition to looking at the hypertension drugs, the study is comparing the effectiveness of a cholesterol-lowering drug to diet alone at reducing death among older hypertensive patients.

Participants in the ALLHAT study, which began in 1994, are aged 55 and older. They have hypertension and at least one additional risk factor for heart attack. Forty-seven percent are white, 35 percent are African American, and 16 percent are Hispanic.


Media Contacts: Karen Richardson, (336) 716-4453 or Mark Wright (336) 716-4587.

Editor''s Note: A press release on this topic is also available from the NHLBI Communications Office (301-496-4236). Results from the trial will also be presented at the American College of Cardiology meeting on March 15.

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