Plasma dopa concentrations after different preparations of levodopa in normal subjects.
The concurrent administration of levodopa with a decarboxylase inhibitor produced a plasma concentration/time curve comparable with 1/4 to 1/5 of the dose of levodopa given alone. There was no evidence to suggest that the decarboxylase inhibitor slowed the rate of elimination of levodopa from plasma. Metoclopramide (Maxolon) increased the rate of levodopa absorption. Higher plasma concentrations of levodopa during the first 2 h after dosing were followed by lower plasma concentrations during the third and fourth hours. The amount of levodopa absorbed after Larodopa as indicated by the AUC was not altered by adding metoclopramide. None of the current preparations of levodopa produced sustained plasma concentrations. In vitro testing confirmed that Brocadopa Temtabs tablets disintegrate and dissolve slowly. In vivo, Brocadopa Temtabs behaved as a slow release preparation but it did not produce sustained plasma concentrations of levodopa.
Department of Physiology, Guy's Hospital Medical School, St Thomas' Street, London SE1 9RT.
J G
JG
Morris
R L
RL
Parsons
J R
JR
Trounce
M J
MJ
Groves
D000328:Adult; D000978:Antiparkinson Agents / Q000493:pharmacokinetics*; D065105:Aromatic Amino Acid Decarboxylase Inhibitors; D001682:Biological Availability; D004295:Dihydroxyphenylalanine / Q000097:blood*; D005260:Female; D006801:Humans; D007980:Levodopa / Q000008:administration & dosage / Q000737:chemistry / Q000493:pharmacokinetics*; D008297:Male; D008787:Metoclopramide / Q000494:pharmacology; D012995:Solubility
D000978:Antiparkinson Agents; D065105:Aromatic Amino Acid Decarboxylase Inhibitors; D007980:Levodopa; D004295:Dihydroxyphenylalanine; D008787:Metoclopramide