L-threo-3, 4-dihydroxyphenylserine treatment of Parkinson's disease.

L-threo-3,4-dihydroxyphenylserine (L-threo-DOPS) was administered at a maintenance dose of 600-900 mg/day, in 10 patients with Parkinson's disease who exhibited a notable freezing phenomenon under the medication of L-DOPA/DCI (DOPA-decarboxylase inhibitor). Changes in clinical symptoms were examined after 8 weeks of treatment. Frozen gait and dysarthria were markedly alleviated by L-threo-DOPS administration, and the rigidity persisting under conventional medication was also relieved. Marked improvement in frozen gait was observed in 1-2 weeks, and that of dysarthria in 2-3 weeks, after the initiation of L-threo-DOPS administration. Nine of the 10 patients were treated with a combination of DOPA and DCI, and the L-threo-DOPS/benserazide ratio and L-threo-DOPS/carbidopa ratio were 9.2 and 26.3, respectively. The effect of L-threo-DOPS were enhanced in one patient in whom DCI was changed from carbidopa to benserazide, suggesting the necessity of further studies on the type and dose of DCI to be combined with L-threo-DOPS.