Influence of ageing on the pharmacokinetics of levodopa in elderly patients with Parkinson's disease.

Levodopa (LD) is the most effective drug to treat the symptoms of Parkinson's disease (PD). It has been reported that the bioavailability of LD is higher in elderly patients than in young patients; however, it is not known how ageing changes the bioavailability of LD among elderly patients. In this study, we compared the pharmacokinetics of LD between two groups of elderly PD patients, early- (75 years or younger) and late-elderly (76 years or older). After oral administration of a tablet containing 100 mg LD per 10 mg carbidopa in 155 PD patients, we measured plasma LD concentrations. Peak drug concentration (C(max)), time to peak drug concentration (T(max)), halftime of drug (T1/2) and area under the curve (AUC) were determined. AUC and T1/2 were significantly higher and longer, respectively, in the late-elderly group than in the early-elderly group (p < 0.05 and <0.05, respectively). However, C(max) and T(max) were not statistically different between the groups. The present data indicate that LD absorption is consistent in PD patients, regardless of age. The difference in oral LD bioavailability between the groups may result from a difference in excretion ability. Physicians should consider LD pharmacokinetics when treating elderly PD patients.