Deprenyl for the Treatment of Early Parkinson's Disease

Abstract

The study of deprenyl by the Parkinson Study Group (Nov. 16 issue)¹ and the rationale for its conclusions and early termination raise a serious concern. Did the investigators observe a delay in the need for treatment among patients with previously untreated Parkinson's disease, or did they observe a reduction in the efficacy of a specific dose of a symptomatic treatment agent that has some effect on the disease itself? In other words, does deprenyl retard the spread of Parkinson's disease, or does it ameliorate the symptoms? The investigators knew that deprenyl had been and still is used as a symptomatic treatment. In fact, they refer to a number of studies that have shown that deprenyl may lessen disability in Parkinson's disease and even extend the lives of patients.^{2 3 4 5 6} Whether or not these studies deserve to be deprecated by being labeled "uncontrolled," they do represent a warning that should have affected the design of the deprenyl study. Unfortunately, that warning was not heeded, and there is now some evidence that deprenyl acted at least to some extent as a symptomatic treatment. To label these apparent treatment effects as "clinically trivial" is to miss the importance of having such effects appear to begin with. The amelioration of symptoms is generally accepted as a sign of the effectiveness of treatment and not of the delay of disease progression. The fact that the amelioration noted was statistically significant appears to contradict the assertion that its effects were trivial and raises the very strong possibility that deprenyl acted in part as an effective symptomatic treatment rather than as a depressant.