A new review of existing research confirms that a weight-loss drug raises blood pressure, posing a risk to obese patients who hope to reduce hypertension by shedding pounds.
Many doctors assume that patients automatically lower their blood pressure when they become thinner, but that is not necessarily the case when they use drugs to lose weight, said review lead author Dr. Andrea Siebenhofer.
In the big picture, "anti-obesity drugs are no wonder pills and should be prescribed only if patients beg doctors for some tablets which help them to lose some weight," said Siebenhofer, a researcher at the Medical University of Graz in Austria.
The review authors examined research regarding three weight-loss drugs — orlistat, sibutramine and rimonabant. They looked for studies that lasted at least six months and compared patients with high blood pressure who took one of the drugs to those who took a placebo.
The analysis appears in the latest issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates medical research. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic.
The researchers found no studies that met their criteria for patients who took rimonabant, known by the brand name Acomplia.
The drug is not available in the United States; in 2007, the Food and Drug Administration declined to approve its sale and asked its manufacturer to provide more information about its safety. In 2008, the manufacturer agreed to suspend its sale in Europe, amid reports that it heightened the risk of suicidal thoughts.
The review authors did find four studies examining each of the other two drugs, orlistat and sibutramine.
Orlistat, known by the brand names Xenical and Alli, is both an over-the-counter and a prescription drug in the United States. Sibutramine is a prescription drug sold under the brand name Meridia.
The researchers conducted a meta-analysis by combining the studies and adjusting the statistical results to account for their sizes.
In those treated with orlistat, blood pressure fell by an average of 2.5 mm Hg systolic and 1.9 mm Hg diastolic.
However, the diastolic blood pressure levels of patients who took sibutramine rose by 3.2 mm Hg, according to the meta-analysis.
Systolic blood pressure is the top number in a blood-pressure reading (like 120/80) while diastolic is the bottom number.
The review of sibutramine research had some limitations. The review authors only looked at two of the four studies into the drug because they believed the other two did not meet the criteria they had set for inclusion in the meta-analysis.
In addition, the researchers reported that the two studies they did include failed to provide enough information to allow them to calculate how the drug affected systolic blood pressure.
Carla Wolper, a member of the research faculty at New York Obesity Research Center at St. Luke's Hospital, said weight-loss drugs have a place in obesity treatment, but that it is important to prescribe them with care and use them in conjunction with other strategies.
A "smart dietician" is crucial to success, Wolper said, as long as he or she "helps people adjust their diet without making a 180-degree change and uses cognitive behavior therapy to challenge people's ideas" about eating.
Wolper acknowledged working on a drug company-funded study into orlistat.
Dr. Raj Padwal, an assistant professor at the University of Alberta in Canada, said the weight-loss drugs only result in modest amounts of weight loss — typically 6 to 11 pounds — but do improve cardiovascular health. Sibutramine is the exception because it raises blood pressure, he said, and a large study is underway to see if it affects death rates in patients.
Only about 2 percent of patients continue to use the drugs after two years and many find the amount of weight lost disappointing, Padwal said. Side effects are also a problem — orlistat can cause loose stools, for instance — and the drugs are expensive, he added.
"There are no magic pills," he said. "These pills may help a minority of people, and I've seen some people lose a lot of weight, but treatment must be supervised by a health-care provider with appropriate monitoring of parameters, such as blood pressure."
Siebenhofer A, et al. Long-term effects of weight-reducing drugs in hypertensive patients. Cochrane Database of Systematic Reviews 2009, Issue 3.
Low-carb diet effective at lowering blood pressure
In a head-to-head comparison, two popular weight loss methods proved equally effective at helping participants lose significant amounts of weight. But, in a surprising twist, a low-carbohydrate diet proved better at lowering blood pressure than the weight-loss drug orlistat, according to researchers at Veterans Affairs Medical Center and Duke University Medical Center.
The findings send an important message to hypertensive people trying to lose weight, says William S. Yancy, Jr., MD, lead author of the study in the Jan. 25 Archives of Internal Medicine, and an associate professor of medicine at Duke. "If people have high blood pressure and a weight problem, a low-carbohydrate diet might be a better option than a weight loss medication."
Yancy added, "It's important to know you can try a diet instead of medication and get the same weight loss results with fewer costs and potentially fewer side effects."
Studies had already indicated that a low-carbohydrate diet and prescription-strength orlistat combined with a low-fat diet are effective weight loss therapies. But the two common strategies had not been compared to each other, an important omission now that orlistat is available over-the-counter. In addition, few studies provide data on these treatments for overweight patients with chronic health issues.
That's what made these findings particularly interesting, says Yancy, a staff physician at the Durham VA where the research was conducted. The 146 overweight participants in the year-long study had a range of health problems typically associated with obesity -- diabetes, high blood pressure, high cholesterol and arthritis.
"Most participants in weight loss studies are healthy and don't have these problems," he said. "In fact they are often excluded if they do."
The average weight loss for both groups was nearly 10 percent of their body weight. "Not many studies are able to achieve that," says Yancy, who attributes the significant weight loss to the group counseling that was offered for 48 weeks. In fact, he says "people tolerated orlistat better than I expected. Orlistat use is often limited by gastro-intestinal side effects, but these can be avoided, or at least lessened, by following a low-fat diet closely. We counseled people on orlistat in our study fairly extensively about the low-fat diet."
In addition to achieving equal success at weight loss, the methods proved equally effective at improving cholesterol and glucose levels.
But Yancy said it was the difference in blood pressure results that was most surprising.
Nearly half (47%) of patients in the low-carbohydrate group had their blood pressure medication decreased or discontinued while only 21 percent of the orlistat plus low-fat diet group experienced a reduction in medication use. Systolic blood pressure dropped considerably in the low-carbohydrate group when compared to the orlistat plus low-fat diet group.
"I expected the weight loss to be considerable with both therapies but we were surprised to see blood pressure improve so much more with the low-carbohydrate diet than with orlistat," says Yancy, who says the mechanism is unclear. "While weight loss typically induces improvements in blood pressure, it may be that the low-carbohydrate diet has an additional effect." That physiologic effect may be the subject of future studies.
The bottom line, says Yancy, is that many diet options are proving effective at weight loss. But it's counseling patients on how to best follow the options that appears to be making the biggest impact. "It is clear now that several diet options can work, so people can be given a choice of different ways to lose weight. But more importantly, we need to find new ways to help people maintain their new lifestyle."