This month's Scientific American describes many of problems faced in getting pharmaceuticals to their intended targets throughout our bodies. Delivering neuropsychopharmaceuticals to our brain remains even more of a problem.

Drug delivery to our brain can occur through several methods: orally (pills), gaseous/inhaled, intramuscularly (skin patch), intravenously, and neural injection.  The method used greatly influences the amount of the drug that is required for the same effect to be observed.  For example, a single dose of an amphetamine creates the same effect but requires hugely different volumes depending on the method of delivery:

• 1000 micrograms if ingested orally
  
• 100 micrograms if injected or inhaled
  
• 10 micrograms if injected in the cerebral spinal fluid
  
• 1 microgram if injected onto the neuron

The primary delivery limiters are the digestive system and the blood brain barrier.  Many effective treatments for mental illnesses have been kept off the market due to the inability to safely deliver therapeutic chemicals whose large molecular sizes makes it impossible for them to pass the blood brain barrier. 

Neural chips may play a role in effectively delivery, but the cultural "acceptability barrier" of implanting chips into our brains will likely remain the largest obstacle to adoption on wide scale for some time to come.  It is one thing if you are deaf and get a cochlear implant, it is another to be willing to go through a surgical procedure if you are a bit anxious or occasionally depressed.  The likely pathway will depend on the pay-off for the patient.  One thing is for sure, more effective drug delivery systems will require new partnerships and new techniques to make precise delivery possible.