High doses of the B−vitamin niacin decrease plaque buildup in the carotid artery far better than the much−prescribed drug ezitimibe, better known as Zetia, according to a recent study. The niacin was administered in the form of the drug, Niaspan. The difference was large enough that the study was stopped before its scheduled ending date.

Ezitimibe and niacin are considered useful in preventing and treating heart disease because of their effects on cholesterol metabolism; ezitimibe lowers LDL (bad) cholesterol, while niacin raises HDL (good) cholesterol.

Statins are the primary medication prescribed to prevent and treat heart disease. They are cholesterol−lowering drugs. When more help is needed, a secondary drug may also be prescribed. One of these is ezitimibe, sold by Merck as Zetia. Merck also sells Vytorin, which is ezitimibe and a statin combined in one pill. Niaspan, high dose niacin in a form that's released steadily over time, is another secondary drug.

Ezitimibe and niacin are considered useful in preventing and treating heart disease because of their effects on cholesterol metabolism; ezitimibe lowers LDL (bad) cholesterol, while niacin raises HDL (good) cholesterol.

In the study, 208 of the 363 subjects completed the full 14 months of treatment before the trial was stopped. All either had or were at high risk for heart disease. They had been taking and continued to take a statin for their condition. Half also took Zetia for 14 months, while the other half took Niaspan. Those who took Zetia showed a reduction in LDL cholesterol but no change in the thickness of plaque deposits in their carotid arteries. Those who took Niaspan showed an increase in HDL cholesterol, a decrease in LDL cholesterol (though not as great as in those who took Zetia) and a decrease in the thickness of plaque in their carotid artery of between 1% and 2%.

Based on the effects on plaque deposits, the study was halted because those in charge felt that the results clearly showed benefit from Niaspan and no benefit from Zetia.

While many doctors are convinced that this clearly shows niacin to be superior to ezitimibe, others question the meaning of the study results. This is primarily because the goal of taking either medication is to reduce the number of heart attacks and death from heart disease. Lowering carotid artery plaque is not universally−accepted as a good measure of this. While more major adverse heart events occurred in those taking Zetia (9 vs. 2 in Niaspan−takers), these numbers are too small to be statistically significant. Some doctors also feel that the study was made less meaningful by its premature termination. With several larger clinical trials of Zetia and of Niaspan currently in progress, they prefer to wait for the results of these studies before rendering a final verdict on Zetia's effectiveness.

But there is broad agreement that the head−to−head trial offers no compelling endorsement of Zetia.

This is not the first time Merck's ezitimbe−containing drugs have tested as ineffective. A large 2008 study showed Vytorin to be no more effective than statin alone in lowering carotid plaque accumulation.

Lurking in the background here are the vast sums of money involved. Zetia and Vytorin had combined sales of about $4.6 billion last year. Merck and its partner, Schering−Plough, agreed to pay over $41 million to settle lawsuits claiming that they delayed releasing unfavorable information on Zetia and Vytorin to prevent decreased sales. The head−to−head study of Niaspan and Zetia was conducted by Abbott Laboratories, who makes Niaspan. Doctors have been prescribing Zetia since 2002. Based on the variety of responses to this latest study, it looks as if some will continue to prescribe Zetia while others will stop doing so.

An article detailing the study was published online by the New England Journal of Medicine on November 15, 2009. Two editorials accompanied this article. Both conclude that Niaspan is preferable to Zetia as a secondary medication for prevention and treatment of heart disease.