Effect of levodopa treatment for parkinsonism in welders - A double-blind study

Background: Manganese is known to cause a parkinsonian syndrome similar clinically to Parkinson disease (PD). L-Dopa responsiveness is a hallmark of PD; however, L-dopa's effect on manganese-induced parkinsonism is not well defined. Objective: To access the efficacy and safety of L-dopa therapy in a double-blind, randomized, placebo-controlled trial. Methods: Thirteen patients with manganese-induced parkinsonism were evaluated in a cross-over study with a modified Unified PD Rating Scale (UPDRS), timed walk test, tapping, and global clinical impression scores. Adverse reactions were assessed. Results: There was no significant difference between placebo and L-dopa for any measure: motor UPDRS, 27.4 vs 28.8; walk time, 16.6 seconds vs 17.7 seconds; tapping right hand, 69.5 vs 64.7; and tapping left hand, 66.8 vs 64.4. There were no differences in the global impression scores. Adverse reactions occurred similarly in the two groups, including headaches, drowsiness, and diarrhea. Conclusions: L-Dopa therapy is not effective for the management of parkinsonism in welders. L-dopa unresponsiveness may be useful to distinguish manganese-induced parkinsonism from Parkinson disease.