So, is this a case of evil pharmaceutical companies trying to gouge consumers over worthless medications? Not exactly. Like every campaign promoting prescription drugs, commercials for Zetia and Vytorin oversold the benefits and did not sufficiently emphasize the risks of these medications. Their failure to improve outcomes in this study is troubling, but because adverse outcomes were so rare overall, it would be difficult to establish an effect one way or another. Also, this study was not geared towards measuring plaques and clots directly; rather it (indirectly) measured the effect of these drugs on atherosclerosis. The effect of uptake blockers on infarction rates was an incidental measurement.
One important consideration when interpreting these results is that the study group was not constructed to resemble the general population. Rather, the study was performed on individuals who had familial hypercholesteremia, a genetic condition that causes greatly elevated levels of LDL in the bloodstream. Without the data in hand I of course cannot make a solid judgment, but one possibility that immediately suggests itself is that in this population even a significant diminution of LDL levels is not sufficient to improve outcomes. There’s just too much cholesterol for these uptake blockers to affect the outcome. In a normal individual with significantly lower levels of LDL Zetia and Vytorin might have a much greater effect.
Moreover, all the individuals in this study were already taking statins—which contributed to the low rate of adverse outcomes. It may be that the marginal improvement from adding an LDL blocker on top of a statin simply isn’t that great. However, for individuals who cannot take a statin due to side effects, taking an uptake blocker might be a significant improvement over doing nothing. The study does not, as far as I can tell, speak to this possibility.
There is always the possibility that this study points to completely unsuspected aspects of arterial disease. For instance, these results might indicate that once lesions form they attract cholesterol very strongly, and therefore only extreme reductions in circulating LDL can affect their growth. Alternately, this outcome may indicate that mechanisms unrelated to circulating lipids play a more significant role in determining plaque thickness than previously suspected. In light of the highly unusual population used as study subjects, any grand pronouncements in this regard are premature. If these findings are replicated in upcoming studies of greater duration on more representative samples, however, a substantial re-examination may be in order.
The findings of the ENHANCE study don’t really indicate that you should burn your Vytorin prescription and go back to just a generic statin, but it does create doubt as to whether this approach will prove efficacious in the general population. Further study, promptly published, is called for, and it would be wise for Merck and Schering-Plough to pull their advertising campaigns for the time being. Doctors should also be less eager to prescribe Vytorin for patients who are responding well to statins alone, but for patients who are not improving greatly with statins (or cannot take them at all), then a prescription for Vytorin (or Zetia) would still seem to be justified. As always, the best approach is to exercise and eat healthy foods, though that’s much easier said than done.