There is conflicting evidence on whether the drugs pergolide and cabergoline significantly increase the risk of heart valve disease among Parkinson’s patients. Most previous studies (but not all) report an increased risk. The pathological features of the valve disease are disturbingly similar to those observed in the late 90s among women who took the “fen-phen” diet drugs, and the Parkinson’s drugs and diet drugs share similar mechanisms of action. But earlier studies in Parkinson’s patients have a variety of design limitations that make it difficult to determine the true significance of the heart valve problem. The news story in the Wall Street Journal accurately states that two new studies in the New England Journal of Medicine show the drugs are associated with a four- to seven-fold increased risk of valve disease. It correctly states that 23% to 29% of Parkinson’s patients in the Italian study had heart valve disease—a disconcertingly high rate. But when it states that “19% of patients” taking these drugs developed heart valve disease in the large United Kingdom cohort, it vastly overstates that study’s results. Considering the billions of dollars in product liability lawsuits generated by the fen-phen disaster, this is a matter of considerable financial as well as medical importance. According to the researchers who analyzed the UK cohort, a total of 2159 patients took pergolide and cabergoline. Among these 2159, 12 developed heart valve disease. On average, the researchers reported (after controlling for the amount of time each patient took the drugs), if 10,000 Parkinson’s patients took pergolide for one year, 30 would develop valve disease; and if 10,000 patients took cabergoline for one year, 33 would develop valve disease. This amounts to a heart valve disease rate of about 0.3% per year for each of the two drugs in the UK cohort (far lower than suggested by the Wall Street Journal story), compared to 23% to 29% in the Italian cohort. The fact that this is four- to seven-times more cases than develops with other Parkinson’s drugs (the relative risk) is likely meaningful—but the inexplicable variance in absolute risk (0.3% per year in one study versus 23% to 29% in the other) suggests that there is still conflicting evidence—and substantial uncertainty–about the true scope of this problem. Despite these caveats, the weight of evidence points to a problem worthy of coverage in the national media. Fortunately for Parkinson’s patients, there are alternative medicines that do not appear to cause heart valve disease.
The news story provides no information on the costs of using these drugs or alternative medicines.
The news article does not quantify the potential benefits of treatment with these two Parkinson’s drugs, instead describing them only in general terms. A little more information – a risk/benefit tally – might help readers weigh their advantages and disadvantages.
By greatly overstating the proportion of patients at risk of heart valve disease in the large UK cohort study, the news article fails to provide balanced information about the frequency and seriousness of harms. (See “Disease mongering” above.) Nevertheless, the two research studies taken together reaffirm the strongly held suspicion that these drugs have the potential for causing valvular disorders.
When a news article reports that a medical treatment appears to cause devastating harm to at least one in five patients, it naturally raises fears—and critical questions: Are there other potential explanations for the disturbing findings? Is there something about the quality of the evidence that makes it especially compelling? Is there something about the quality of the evidence that should make us think twice? Considering the seriousness of the charges—that two Parkinson’s drugs “sharply increase the risk of heart-valve disease”–the news article’s discussion of the scientific evidence is inadequate. As carefully conducted as the studies in the New England Journal of Medicine are, neither is capable of examining and adjusting for all of the factors that might account for an increased incidence of valve disease. Indeed, the absolute risk of developing valve disease was inexplicably very different from one study to the other– about 0.3% per year per drug in the UK cohort, compared to 23% to 29% in the Italian cohort. (See “Disease mongering” above.) Also, because the news article gets an important fact wrong and vastly overstates the risk of valve disease in the UK study (saying it is 19%), it fails to point out this discrepancy. As a result, the questions, “Which rate should we believe—and why?” aren’t asked, much less answered. There is likely no simple answer, and maybe no complex answers either. But that is all the more reason to explain the strength of the evidence to readers.
The news article misinterprets key data in the study about Parkinson’s patients in the United Kingdom, thus highly inflating the occurrence of heart valve problems in patients taking the two Parkinson’s drugs. In the UK cohort, 31 of 11,417 Parkinson’s patients taking a variety of drugs developed heart valve disease. Of these 31 patients, 6 (19%) had taken the drug pergolide (brand name Permex), and another 6 (19%) had taken the drug cabergoline (Dostinex). However, the news story wrongly writes, “In one study in the United Kingdom, 19% of patients taking pergolide or cabergoline suffered heart-valve damage…” If that were the case, there would have been hundreds more cases than actually reported. According to the published study, 931 patients took pergolide and 1228 received cabergoline. The researchers concluded that if 10,000 patients took pergolide for one year, 30 would develop valve disease; if 10,000 took cabergoline for one year, 33 would develop valve disease. This amounts to a valve disease rate of about 0.3% per year per drug—far fewer than was suggested by the news story. The article accurately notes that valve disease was five to seven times more likely to occur among the UK patients taking one of these two drugs, and similarly risky in the smaller, second study from Italy.
The article enlists a variety of sources to balance its commentary on the drugs implicated in the new research, and includes sufficient information for readers to assess the sources’ potential conflicts of interest.
The news story summarizes the main alternative to the two drugs associated with heart valve disease. (“The main treatment is a medicine called levodopa, which the body converts to dopamine…”) However, it neglects to mention whether levodopa also has side effects that readers might want to evaluate. More importantly, it fails to point out that other medicines in this drug class (e.g. lisuride, pramipexole, ropinorole) are available which are not associated with heart valve disease, information readers might find useful and reassuring.
The Wall Street Journal article provides accurate information about the availability and stormy history of two Parkinson’s drugs that may increase the risk heart valve disease.
Physicians have treated Parkinson’s patients with the drugs pergolide and cabergoline for a long time. The news article accurately represents their controversial history, though it neglects to note that other medicines in this drug class are avaliable that do not appear to cause heart valve disease.
No obvious use of text from the press release.