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I'm looking at this article on the possible mechanism of detoxifying brain during sleep using cerebrospinal fluid. It states that at night, the space between neurons may allow better (up to 20x) circulation of cerebrospinal fluid within the brain to clean out metabolic by products of daytime activity.

My question is if this may also work in reverse and allow to deliver drugs within the fluid to the brain. If a person ingests a drug or nutrient before sleep, would the increase in circulation of cerebrospinal fluid deliver the drug to deep regions of the brain? Or does the blood-brain barrier prevent drugs from entering cerebrospinal fluid?

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Certain drugs can cross blood-brain barrier. In such cases your hypothesis should be correct. – WYSIWYG Jan 22 '14 at 13:24
up vote 3 down vote accepted

Only certain drugs can cross the blood brain barrier (BBB). However, there exist techniques to deliver drugs to the brain that otherwise cannot permeate through the BBB. One such technique is called intrathecal delivery that injects drugs directly into the cerebrospinal fluid, avoiding the BBB problem and allowing the drug to reach cells, including neurons, in the brain. It has been used for certain kinds of chemotherapy, pain management, treatment of spastic cerebral palsy, and more recently for enzyme replacement therapy. However with intrathecal delivery there is a risk of infection.

Having said that, if a drug reaches the CSF then your hypothesis should be correct. There is no experimental evidence for it yet.

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