Parkinson's drug may raise risk of valve trouble

In some cases, patients taking a Parkinson's drug called cabergoline may experience damage to heart valves, a study suggests. High cumulative doses of and long-term treatment with this drug are risk factors for the development of "valvulopathy," Japanese doctors report in the journal Neurology this month.

Cabergoline is a so-called dopamine agonist used to control movement problems caused by Parkinson's disease. Other dopamine agonists include pergolide and pramipexole.

Dr. Mitsutoshi Yamamoto and colleagues determined the frequency of valvulopathy in 210 consecutive Parkinson's patients admitted to Kagawa Prefectural Central Hospital in Takamatsu.

Among the 125 dopamine agonist-treated patients, 16 received cabergoline, 66 received pergolide, 16 pramipexole, and 27 were past users of a dopamine agonist. The remaining 85 patients were not treated with any dopamine agonist and served as the control group.

According to the investigators, the frequency of valvulopathy was significantly higher in the cabergoline-treated patients relative to control patients (68.8 percent vs 17.6 percent). The frequency was similar between pergolide-treated and pramipexole-treated patients (28.8 percent and 25 percent, respectively).

The adjusted odds ratio for valvulopathy was 12.96 in the cabergoline group, 2.18 in the pergolide group and 1.62 in the pramipexole group, relative to no treatment with dopamine agonists.

The investigators point out that the mean daily dose was higher for cabergoline (3.8 mg) than for pergolide (1.4 mg) or pramipexole (1.7 mg).

Moreover, in looking at patients with and without valvulopathy, the cumulative dose and treatment duration of cabergoline was significantly higher in patients who developed valvulopathy.

These results need to be confirmed in a larger series of patients, Yamamoto and colleagues say.

"Interestingly," they add, the frequency of valvulopathy was similar in the past-treated group and the control group. "Whether this result is due to discontinuation of the drug or it means that valvulopathy caused by these types of drugs is reversible remains to be clarified," they write.

The investigators also mention in their report that none of the patients had clinically significant symptoms of valvular heart disease, such as shortness of breath. "However, as pointed out by others, lack of symptoms does not mean that this kind of valvulopathy poses no significant safety problem," they write.

Therefore, they conclude that periodic heart valve testing is "essential" when cabergoline or pergolide are used at a high dose.

SOURCE: Neurology October, 2006.