This document discusses strategies for targeted drug delivery to the brain. It begins by introducing the challenges of drug delivery across the blood-brain barrier (BBB), blood-cerebrospinal fluid barrier, and blood-tumor barrier. It then describes various approaches researchers have developed to enhance central nervous system drug delivery, including using lipophilic analogs, prodrugs, carrier-mediated delivery, and vectors. The document also discusses methods for temporary disruption of the BBB, such as using hypertonic solutions or biochemical agents. Promising strategies highlighted include liposomes, nanoparticles, implantable drug reservoirs, and systems based on enzymatic activation. The overall goal is to develop treatments for diseases of the brain and central nervous system.