The influence of age on the kinetics of a standard oral dose of levodopa administered with an inhibitor of peripheral dopa decarboxylase enzymes (benserazide) has been evaluated in 40 patients with Parkinson's disease (age 34-78 y) on chronic therapy. They were divided into 2 groups, on the basis of age below (21 patients, Group A) or above (19 patients, Group B) 65 y. The area under the plasma concentration-time curve (AUC) of levodopa was significantly greater in the older group (547 versus 428 μmol·1-1·min in Group B), coupled with a reduced apparent oral clearance (8.1 versus 10.7 ml·min-1 ·kg-1) and a longer plasma elimination half-life (67.6 versus 54.6 min). The age of the patients was positively correlated with the AUC of levodopa (r=0.474) and its plasma elimination half-life (r=0.391), and was negatively correlated with clearance (r=-0.489). The findings confirm previous data on volunteers that showed a reduction in the systemic clearance of levodopa due to age, which would probably account for the finding of a greater AUC of levodopa in older patients. The observed, age-mediated differences in levodopa pharmacokinetics, albeit statistically significant, were moderate and were likely to be of only minor importance for the dosing schedule.
- Parkinson's disease
ASJC Scopus subject areas
- Pharmacology, Toxicology and Pharmaceutics(all)
- Pharmacology (medical)