R-(-)-deprenyl as an adjuvant to levodopa in the treatment of Parkinson's disease.

As an adjuvant to levodopa, deprenyl (selegiline) has proved to have a significant beneficial effect in about 50-60% of patients with a deteriorating response to levodopa which has become complicated by fluctuations in disability. The addition of deprenyl to levodopa treatment improves both parkinsonian disability and fluctuating responses, particularly end-of-dose failure. Deprenyl is simple to administer (5-10 mg/day) and free from serious toxicity. It is possible to reduce the levodopa dose by 20-50% when deprenyl has been instituted, thus decreasing the frequency of side effects. During long-term treatment with deprenyl there is a clear-cut decline in the degree of therapeutic responses, due to the progression of the underlying Parkinson's disease. However, there is evidence that the life expectancy of these patients may be increased. Thus it is advisable to give deprenyl not only as a first adjuvant to levodopa in advanced patients but right from the early phase of the disease, hoping that it will render Parkinson's disease more benign, with long-term symptom control, fewer late complications and increased life expectancy.