Carbidopa-Levodopa Ratio in Parkinson's Disease

To the Editor.—

The recent report by Tourtellotte et al (Archives1980; 37:723-726) describing their study of the use of an increased ratio of carbidopa to levodopa in the treatment of Parkinson's disease is rather difficult to interpret. The authors used an investigational design that allowed them to study three separate groups of patients with Parkinson's disease who had ceased receiving levodopa or carbidopa-levodopa (10:100) for at least one month. These groups of patients were treated with either levodopa, carbidopa-levodopa (10:100), or carbidopa-levodopa (20:100), and their degree of parkinsonian disability was evaluated. The response of the patients to these three different treatment regimens after a two-week period was used to conclude that increasing the amount of carbidopa in presently available drugs is a desirable treatment modality. Although the authors do state that their study "was conducted over a relatively short period," Parkinson's disease, in particular the therapy of Parkinson's disease