How is CNS drug distribution?

Needs liposoluble drugs transport is primarily transcellular (not paracellular cause of increased tight junctions) Imp for side effects Ex: Loratidine antihistamine is non sedating as it is hydrophilic whereas diphenhydramine could cause sedation with antihistamine effect Drugs may enter CNS by specific uptake transporters into brain and CSF Also output is possible by efflux carriers (like Pgp, or OATP (also seen in GI))