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The drug delivery to the brain system is a most challenge to the scientist for developing the drug designed for CNS. The major problem is that all the drugs does not passes through BBB, only nanoparticles and highly lipid soluble drugs may pass through. The BBB is a most essential barrier between the circulating blood and the neural tissue. The criteria for drug delivery includes the following, a) the drug must be stable, b)the drug must have access to brain, c) the dose should be sustained and controlled, d) the effect of drug should be localized. The drug may administer either by systemic administration or by direct delivery of drugs into the brain. The polymers which plays an most important role in the advancement of drug delivery technology by providing controlled release of therapeutic effect, administered in the constant dose over a long period of time. The BBB maintains the brain homoeostasis as well as movement of ion and molecule. Failure in this process results in breakdown of brain cell structure. This may leads to a disease such as Parkinson disease and Alzheimer’s disease.