Protective and preventive therapeutic strategies: monoamine oxidase inhibitors.

There is convincing evidence that monotherapy with 10 mg of selegiline daily substantially delays parkinsonian disability, although whether this delay is due to a symptomatic or protective mechanism remains a matter of debate. Evidence against a symptomatic effect is that the wash-out evaluation in two double-blind, placebo-controlled studies failed to detect clinical decline 1 month after discontinuing selegiline. Yet it can be argued that 1 month was not long enough to eliminate the biologic effect of the drug. Thus further studies are required to answer this question definitively. Nonetheless, because selegiline delays the requirement for levodopa therapy and appears to be relatively safe when used as monotherapy, it seems reasonable to recommend this drug as initial treatment when Parkinson's disease is first diagnosed. There is little doubt that future therapeutic and diagnostic strategies for Parkinson's disease and other neurodegenerative diseases will be profoundly influenced if this drug is unequivocally demonstrated to slow progression of Parkinson's disease. Such a finding would be a potent argument for developing biomarkers of preclinical disease because early intervention with such protective therapy might even halt the disease before symptoms develop.