Subarachnoid Distribution of Drugs after Lumbar Injection

Abstract

DIRECT injection of drugs into the subarachnoid space is required for treatment of several diseases involving the leptomeninges. This is necessary because of the virtual exclusion of certain plasma constituents by the bloodcerebrospinal-fluid barrier due to molecular size, protein binding, lipid insolubility or ionization.2 Drugs included in this category are polymyxin B and amphotericin B.3 , 4 The antimetabolites 6-mercaptopurine and methotrexate, used in the therapy of acute leukemia, do not attain significant levels in spinal fluid when administered systemically.2 , 5 Therefore, meningeal leukemia, the diffuse involvement of the meninges by leukemic cells, must often be treated with an intrathecally administered drug such . . .