抗氧化物減低降膽固醇藥物的效用

維他命雞尾酒療法會轉化高密度脂蛋白的效應

  雖然抗氧化物與降膽固醇藥物在預防心臟病上均各有功效,但根據一些最近驚人的發現,醫師們仍需多關切他們病人所服用的藥物。一份在八月Arteriosclerosis, Thrombosis and Vascular Biology: Journal of the American Heart Association期刊上的研究,研究人員發現在傳統的降膽固醇藥物中加入抗氧化物,會減低他們提高高密度脂蛋白的效益。主筆人Marian C. Cheung, PhD.表示:「很明顯地,經由某種特別的方式,抗氧化物會減弱降膽固醇藥物的助益。這是第一次有人發現,像這種能在藥櫃輕易取得的抗氧化物有這樣的效用。而這也確實令我們感到訝異。」

Antioxidants Blunt Effect of Cholesterol-Lowering Drugs

Vitamin Cocktail Has Adverse HDL Effects

By Aman Shah, MD
WebMD Medical News

Reviewed by Michael W. Smith, MD

Aug. 10, 2001 -- As both antioxidants and cholesterol-lowering drugs gain momentum in the prevention of heart disease, doctors need to pay careful attention to what their patients are taking, according to surprising new findings. In a study published in the August issue of Arteriosclerosis, Thrombosis and Vascular Biology: Journal of the American Heart Association, researchers found that when added to conventional cholesterol-lowering drugs, antioxidants can blunt their beneficial effect on raising HDL.

"Antioxidants appear to impair the benefits of cholesterol-lowering drugs, and the antioxidants do this in a very specific way," says lead author Marian C. Cheung, PhD. "This is the first time that anyone is reporting that an antioxidant like those that are available over-the-counter can have this effect. This was very surprising to us."

"The study was designed to determine if antioxidants could have an effect on the endothelium. We didn't expect to find an effect on serum lipids," Cheung, associate professor of medicine at the University of Washington in Seattle, tells WebMD.

The researchers randomized 153 patients with coronary artery disease to receive simvastatin (Zocor) and niacin (group 1); an antioxidant cocktail containing vitamins E and C, ß-carotene, and selenium (group 2); both (group 3); or placebo (group 4). Lipoprotein levels were assessed over a 12-month period.

They found that only patients taking simvastatin and niacin (groups 1 and 3) had any significant changes in lipid profiles. And even though both groups 1 and 3 had similar changes in total cholesterol, triglycerides, and LDL, there was a significant difference in their effectiveness on HDL.

Simvastatin and niacin alone were able to increase HDL by 25%, but when antioxidants were added, an increase of only 18% was seen. Interestingly, when the researchers looked at changes in the levels of different HDL particles, they found that patients in group 1 had a 42% increase in HDL2, whereas HDL2 in group 3 patients was unchanged.

Lewis H. Kuller, MD, PhD, professor and chairman of the department of epidemiology at the University of Pittsburgh School of Public Health, tells WebMD that the new findings "are consistent with other clinical trials that have found vitamin E to have no benefit in primary prevention."

In an editorial accompanying the study, Kuller writes, "Antioxidant vitamin combinations above the recommended daily allowances should not be recommended for prevention or treatment of cardiovascular disease." He also advises physicians to warn patients that combining antioxidants with cholesterol-lowering drugs could be hazardous.

Kuller says that antioxidants are popular because "people like to have magic bullets, and doctors are like everybody else in that they often believe it is easier to swallow a pill." He says that instead of chasing miracle vitamin combinations, physicians and patients should concentrate their efforts on "effective and proven" methods to prevent and treat heart disease. "That is where the emphasis should be," he says.

"The antioxidant hypothesis is probably correct but limited. We just don't understand the oxidative process in the arterial wall. We don't understand the mechanism. ... It may turn out that there are some people who benefit," he says.

The problem, says Kuller, is that taking findings from observational studies, which should be hypothesis-generating, and applying those findings to clinical practice is both bad science and bad medicine. In some ways, he says, the antioxidant hypothesis parallels the HRT story, but "at least with HRT there is a rational, biologic basis for the practice, although clinical trial data are not there."

Kuller says, too, that he disagrees with antioxidant proponents who say, "'The real problem is that you have to take these [antioxidants] as a food because when they are taken as a vitamin supplement the effect is different.' That is sheer nonsense ... and very poor science based on very shaky data."

Cheung is a little more circumspect. "The antioxidant theory is very popular, and we had no idea that we would find an effect on lipids," she says, although she is unwilling to make a general recommendation based on this study alone. "I think it is too soon to say what should be done about antioxidants."

With reporting by Peggy Peck

 

© 2001 WebMD Corporation. All rights reserved.

    
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