L-dopa treatment and Parkinson's disease.

Seventeen years after its introduction, L-dopa, now administered in combination with a peripheral dopa decarboxylase inhibitor remains the most effective palliative remedy for Lewy body Parkinson's disease. A therapeutic effect to large doses is so consistent that alternative diagnoses should be considered in any patient with a Parkinsonian syndrome who fails completely to respond. Despite improving the quality of life, it probably does not influence appreciably the reduced life expectancy in Parkinson's disease and the long-term therapeutic response is frequently marred by drug-induced oscillations in motor performance, dyskinesias and psychotoxicity. Experimental studies using continuous intravenous infusions of L-dopa in order to obtain constant plasma levels suggests that additional refinements in management may be achieved by the design of a practical controlled delivery system, and prototype pumps and sustained release formulations are already under evaluation.