Two separate studies both concluded that Permax and Dostinex significantly increased the occurrences of heart valve problems in Parkinson's patients. The first study found that patients taking pergolide (Permax) were at least 7.1 times more likely to develop heart damages than those taking other drugs. Those people taking the highest doses were at a risk 37 times greater.

Patients taking cabergoline (Dostinex) were 4.9 times more likely to develop heart valve damages compared to those utilizing other drugs. At the highest doses, the risk was 50.3 times greater.

The second study involved examination of 245 people, 155 of whom had Parkinson's population. The people were then placed into four groups: (1) those Parkinson's patients who were given pergolide (Permax); (2) those Parkinson's patients who were given cabergoline (Dostinex); (3) those Parkinson's patients who received an alternative treatment; and (4) the non-Parkinson's patients, who were given nothing.

The study found that 23.4% of patients taking pergolide (Permax) and 28.6% of those taking cabergoline (Dostinex) suffered heart damage, compared with just 5.6% in the control group.