Increased dosage of carbidopa in parkinsonian patients on low carbidopa-levodopa regimen. Effect on levodopa bioavailability.
The effect of a 2.5-fold increase in daily carbidopa intake on the bioavailability of levodopa was studied in six patients with Parkinson's disease on a low chronic regimen of carbidopa-levodopa (Sinemet) at the fixed ratio of 1:10. The extent of levodopa absorption, expressed as the area under the 11-h plasma levodopa concentration-time curve (AUC0-11 h), was not enhanced by the higher carbidopa dose. A significant increase in the AUC was found for the levodopa metabolite 3-O-methyldopa at the higher carbidopa intake. Clinical performances of individual patients were identical with both carbidopa-levodopa ratios. From these data, an adequate inhibition of peripheral decarboxylation and hence a good bioavailability of levodopa may be expected in patients taking low doses of carbidopa-levodopa, using currently available commercial preparations.
Contin
M
M
Institute of Neurology, University of Bologna, Italy.
Riva
R
R
Martinelli
P
P
Procaccianti
G
G
Baruzzi
A
A
D000368:Aged; D000369:Aged, 80 and over; D001682:Biological Availability; D002230:Carbidopa / Q000008:administration & dosage* / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007980:Levodopa / Q000097:blood / Q000493:pharmacokinetics* / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000188:drug therapy*; D014443:Tyrosine / Q000031:analogs & derivatives / Q000097:blood
D014443:Tyrosine; D007980:Levodopa; D002230:Carbidopa; C008404:3-methoxytyrosine