ABSTRACT
Levodopa (L-3,4-dihydroxyphenylalanine) is the most effective drug available for the treatment of Parkinson’s disease. It is rather unique in that the drug itself and many of its metabolites are naturally synthesised in the body. Therefore the understanding of its metabolism and the concomitant use of other drugs to modify its metabolism may improve the clinical effect. The individual variability in its metabolism may play an important role in the clinical response to this drug. This variability can be classified respectively as intraindividual and interindividual. The interindividual variability refers to the different characteristics of a patient in comparison with another, the intraindividual one mainly depends on the personal situation and external factors, both varying from time to time. On the timing scale, the interindividual variability is the variability among
individuals at one time point; the intraindividual variability is the vari ability in an individual at different time points. Moreover, the metabolic variability of levodopa metabolism-modifying drugs adds another level of variation.
