Direct access of drugs to the human brain after intranasal drug administration?

It has been suggested that intranasal (IN) drug delivery could be used to administer drugs directly to the brain, bypassing the blood-brain barrier. Conclusive evidence of this proposed route of drug transport has not been observed by IN-IV comparison. In eight neurosurgery patients with a CSF drain, the uptake in CSF and plasma after IN and IV drug administration was compared. No evidence of direct access of the drugs from the nose to the CSF was found.