The vitamin niacin can cause unpleasant side-effects when taken with cholesterol-lowering statins, researchers warn today.
The problems affect people who suffer from narrowing of the arteries, researchers found.
Side effects include itching, rashes, indigestion, diabetes and muscle problems.
In the largest randomised study of its kind into niacin, also known as vitamin B3, researchers wanted to see if prescribing extended-release niacin with laropiprant (ERN/LRPT), in addition to an LDL cholesterol-lowering statin, simvastatin, could reduce the risk of heart disease and stroke in people who are already at high risk due to existing occlusive arterial disease (narrowing of the arteries).
The results from the HPS2-THRIVE study, which stands for Heart Protection Study 2 – Treatment of HDL to Reduce the Incidence of Vascular Events, are published online today (27 February ) in the European Heart Journal.
Niacin is used to help increase levels of “good” HDL cholesterol and to decrease levels of “bad” LDL cholesterol and triglycerides in people who are at risk of heart disease and stroke.
However, it causes a number of side-effects, including flushing of the skin. The drug laropiprant can reduce the flushing by blocking the prostaglandin D2 receptor.
A total of 25,673 patients from China, the UK and Scandinavia took part in the study between April 2007 and July 2010. They were randomly split into two groups, one of which received 2g of extended release niacin plus 40 mg of laropiprant, with the other taking a matching placebo.
All participants received intensive LDL cholesterol-lowering therapy with simvastatin (with or without ezetimibe).
Researchers from the Clinical Trial Service Unit & Epidemiological Studies Unit at the University of Oxford, England, followed the patients for an average of 3.9 years.
By the end of the study, 25% of those taking ERN/LRPT had stopped their treatment, compared with 17% of patients taking placebo.
The main reason for patients stopping the treatment was because of adverse side-effects, such as itching, rashes, flushing, indigestion, diarrhoea, diabetes and muscle problems.
Researcher Professor Jane Armitage said: “We found that patients allocated to the experimental treatment were four times more likely to stop for skin-related reasons, and twice as likely to stop because of gastrointestinal problems or diabetes-related problems.”
Patients in the experimental group were more than four times at risk of myopathy (muscle pain or weakness with evidence of muscle damage) compared with the placebo group.
Prof Armitage described this as “highly significant”.
“It appeared that this effect was about three times greater among participants in China than those in Europe, for reasons that are not clear,” she said.
“In the placebo arm, the statin-related myopathy was more common among participants in China than those in Europe.”
Dr Richard Haynes, clinical co-ordinator at the CTSU, said the trial provided “uniquely reliable results” on adverse side-effects.
“Although 25% of patients stopped the treatment early, 75% continued on it for approximately four years,” he said. “Currently, we are analysing the final data on the cardiovascular outcomes from the trial, and once we have these we will know whether or not the benefits of the treatment outweigh the myopathy, skin and gastrointestinal problems.”
The researchers will present full results at the annual meeting of the American College of Cardiology in March.
Haynes R, Jiang L et al. HPS2-THRIVE randomized placebo-controlled trial in 25 673 high-risk patients of ER niacin/laropiprant: trial design, pre-specified muscle, and liver outcomes and reasons for stopping study treatment. European Heart Journal. doi:10.1093/eurheartj/eht055
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