Zetia and Vytorin, both non-statin cholesterol lowering drugs, have been on the market for several years. Even so, no one really knows how well Zetia and Vytorin actually work. That’s because the drugs’ manufacturers have refused to release the results of a clinical trial on their effectiveness, even though it was completed nearly two years ago. Now, the refusal of Merck and Schering-Plough to release the Zetia and Vytorin study results has cardiologists up in arms, with many complaining that the absence of the study’s findings make it difficult for them to effectively treat their patients.
Zetia and Vytorin are marketed as a joint venture between Merck and Schering-Plough. Zetia was the first to be approved by the Food & Drug Administration (FDA) in 2002, and Vytorin followed in 2004. The FDA approved Zetia on the basis of trials that showed it could lower LDL, or so-called bad cholesterol, by 15 to 20 percent. Unlike other cholesterol lowering drugs called statins, Zetia has not been proven to prevent heart attacks, and it is usually prescribed in combination with a statin. Vytorin is a single pill that combines Zetia with simvastatin, the active ingredient in Merck’s Zocor statin. Zetia and Vytorin have become big sellers for Merck and Schering-Plough. According to the New York Times, 800,000 Zetia and Vytorin prescriptions are written every week, and the drugs rack up sales of $4 billion a year.
Those figures are stunning, especially considering that no one really knows if Zetia and Vytorin are more effective than other, cheaper cholesterol lowering drugs. But what is more surprising is why this is so. Merck and Schering-Plough began a clinical trial of the effectiveness of Vytorin and Zetia in 2002. The study, called Enhance, involved 720 patients with very high cholesterol. The data from the Enhance trial was supposed to be released by March 2007, but that didn’t happen. The doctor who supervised the Vytorin and Zetia trial told the New York Times that the drugs’ makers, who controlled the Enhance study’s raw data, blocked its release, citing concerns over accuracy.
Cardiologists aren’t happy about that, and have complained loudly to both Merck and Schering-Plough. The companies recently made a concession, saying they would release a portion of the Vytorin and Zetia trial results in March, but not the entire study. Merck and Schering-Plough also said that they have changed the main medical result – called the endpoint – that the Enhance study is supposed to measure. The companies now say that they will use only partial results to assess the trial’s success in deterring the formation of plaque that can cause artery blockages and lead to heart attacks. But it is generally accepted among scientists that for a clinical trial to be valid, the endpoint must be established before it begins and never changed.
The drug manufacturers’ decision regarding the Vytorin and Zetia clinical trial has done little to quiet the criticism coming from cardiologists. Because Zetia has not been proven to prevent heart attacks, these doctors argue that they must have access to any and all study results relating to its ability to do so. Cardiologists are worried that if these medications don’t prevent heart attacks as well as other cholesterol lowering drugs, then patients taking Zetia and Vytorin are being put at an unnecessary risk of having a heart attack.