It takes time to perform thorough studies of most medical issues, so it was a full year later that the New England Journal of Medicine published three studies that further examined the relationship between heart-valv e disease and use of Adipex. Interestingly, all three studies show an association between use of this medication and heart-valve disease, but the percentage of people affected differs greatly.

In the first study, researchers evaluated echocardiograms -- images of the heart created by sound waves -- of patients who had used, or were still using, this appetite suppressant between January 1994 and August 1997. However, among patients who had taken this drug, the rate ranged from 13-26%!

The second study used computerized medical records to follow four groups of patients: those taking Adipex, those taking fenfluramine, those taking phentermine, and those who had never taken appetite suppressants. None of these patients showed evidence of heart disease at the start of the follow-up period. Over the next four years, investigators found no new cases of heart-valve disease among patients who had never used diet drugs.

They also observed that the risk of developing these problems appeared low in people who had used Adipex or fenfluramine for fewer than three months. However, data suggested that the risk was significantly higher in patients taking either of these medications for more than four months. The number of people taking phentermine was too small to draw any meaningful conclusions about that drug.

In the third study, echocardiography was performed on patients taking regular and long-acting forms of dexfenfluramine and on patients taking a placebo. There was a significantly higher rate of aortic-valve or mitral-valve regurgitation among patients taking the diet drugs compared with those taking a placebo. But when researchers applied the more stringent FDA criteria for valvular disease, the proportion of people affected was only slightly higher in the group treated with dexfenfluramine. This difference was not considered statistically significant.

Given these new reports, how much more do we know about the link between these diet drugs and heart-valve diseases? A little, perhaps, but the story is far from clear.

Certainly, the data from these studies support the theory that use of these medications, particularly for long periods or at high doses, is associated with heart-valve damage. However, the diagnosis of heart-valve disease can be slippery. There are, unfortunately, no simple tests -- like measuring a substance in the blood -- to assess heart-valve function. Physicians must rely on visual interpretation of an image.