L-dopa pharmacokinetics in plasma and cisternal and lumbar cerebrospinal fluid of monkeys.
The pharmacokinetics of levodopa (L-dopa) in plasma and in cisternal and lumbar cerebrospinal fluid (CSF) were studied in Rhesus monkeys that were given 2- to 3-hour intravenous infusions of L-dopa. Steady-state L-dopa concentrations in cisternal CSF correlated well with plasma levels, and yielded a CSF:plasma ratio of 0.17. The disappearance of L-dopa from plasma and cisternal CSF compartments fits an open, two-compartment pharmacokinetic model. Although slower, the distribution and elimination half-lives for L-dopa from cisternal CSF (8.9 and 49.2 minutes, respectively) were of a similar magnitude to those from plasma (4.9 and 33.2 minutes, respectively). If cisternal CSF reflects brain extracellular fluid, then plasma pharmacokinetics of L-dopa are a reasonable approximation of those in the brain. In contrast to cisternal CSF, the disappearance of L-dopa from lumbar CSF fits an open, one-compartment model with an elimination half-life of 100 minutes. This indicates that the lumbar CSF compartment is unsuitable for investigation of the pharmacokinetics of L-dopa in the brain.
Hammerstad
J P
JP
Department of Neurology, Oregon Health Sciences University, Portland 97201.
Woodward
W R
WR
Gliessman
P
P
Boucher
B
B
Nutt
J G
JG
D000818:Animals; D005260:Female; D007275:Injections, Intravenous; D007980:Levodopa / Q000134:cerebrospinal fluid / Q000493:pharmacokinetics*; D008253:Macaca mulatta
D007980:Levodopa