Comparison of levodopa with carbidopa or benserazide in parkinsonism

The therapeutic efficacy and side-effects of two preparations of levodopa with extracerebral decarboxylase inhibitors have been compared in 19 patients with idiopathic parkinsonism in a blind randomised crossover trial. The mean daily dose of levodopa was 658 +/- 64 mg/day (mean +/- S.E.M.) when given together with carbidopa 66 mg/day and 605 +/- 59 mg/day when levodopa was combined with benserazide 151 mg/day. There was no significant difference between the treatment regimens either in beneficial effects on parkinsonian symptoms and signs or in the adverse effects of levodopa assessed by a clinical observer unaware of the treatment given. Of the 19 patients studied, 9 preferred the carbidopa preparation, 8 preferred the benserazide preparation, and 2 had no preference. It is concluded that there is no significant difference in therapeutic effects or adverse reactions between the two commercially available decarboxylase inhibitor-containing preparations. Central-nervous-system actions and side-effects depend on the daily dose of levodopa, regardless of the different ratios of decarboxylase inhibitors to levodopa.