['Increasing drug penetration through the spinal meninges should improve epidural analgesia/anesthesia by increasing the rate and extent to which epidurally administered drugs redistribute to the spinal cord. Palmitoyl carnitine has been shown to improve drug penetration through the intestinal mucosa. The purpose of this study was to determine whether palmitoyl carnitine improves drug penetration through the spinal meninges.', 'The transmeningeal flux of morphine, mannitol, bupivacaine, and sufentanil was determined through the spinal meninges of Macacca nemestrina monkeys before and after addition of palmitoyl carnitine. Flux was determined using a previously established in vitro diffusion cell method.', 'Palmitoyl carnitine significantly increased the transmeningeal flux of mannitol, morphine, and bupivacaine by 942 +/- 102%, 401 +/- 43%, and 12 +/- 4%, respectively. However, palmitoyl carnitine had no significant effect on the transmeningeal flux of sufentanil. The penetration-enhancing effect of palmitoyl carnitine was shown to depend on the dose of palmitoyl carnitine added and on the octanol:buffer distribution coefficient of the study drugs but not on the concentration of the study drug.'] Does palmitoyl carnitine increase the transmeningeal flux of hydrophilic but not hydrophobic compounds in vitro?