A comparative clinical investigation of the therapeutic effect of levodopa alone and in combination with a decarboxylase inhibitor (carbidopa) in cases of Parkinson's disease.

The therapeutic effect of the combination of levodopa and carbidopa ("Sinemet") was compared with that of levodopa alone in 21 patients with Parkinson's disease. Eighteen parameters of the clinical condition and of functional impairment were determined quantitatively and the results satistically evaluated. Changing over from levodopa to the combination preparation resulted in an average improvement of 51.9% within 2 weeks. No relationship was found to exist between the degree of improvement and the severity or the progression of the disease. By the use of the combination preparation, the daily dosage of levodopa could be reduced by 77%. Side-effects connected with the gastro-intestinal tract occurred much less frequently, while hyperkinesia increased. No arrhythmogenic effect was found with the combination product. From the clinical standpoint, combination therapy appeared to be qualitatively superior. By selective maintenance of freshly formed dopamine, it should be possible to assure a directed influence on the disturbed equilibrium of the functional systems of the brain.