I recommend this book, however, it is not easy reading. This is due to the amount of information and quoted studies, etc...
Below are quotes from the book:
Ordinarily, the smallest blood vessels of the body - the capillaries - are lined by endothelial cells which permit the movement of chemicals in and out of the vascular spaces. However, the endothelial cells in the capillaries of the b rain are glued tightly together - a process in which the glial cells (astrocytes) play a prominent role. The "blood brain barrier" prevents the penetration of large molecules, hydrophilic substances (water-liking, low fat soluble molecules), and/or any compound with a high electrical charge. The purpose of this barrier is to protect the central nervous system from toxins, infections, and other biochemical stressors in order to provide a stable environment for the brain. Perhaps the most significant aspect of psychopharmacology is the fact that each medication is a molecule which scientists have specifically designed in order to evade the blood brain barrier. One would hope that this fact would encourage consumers and clinicians to reflect cautiously upon the use of psychoactive drugs, as they are all produced with the intention of eluding the body's natural defenses. (page 46)
For the first twenty years of the modern psychopharmacology era (1950-1970), researchers studied the effects of medications upon the neurotransmitters synthesis and turnover (i.e., the rates of production and metabolism). As a result, the biological theories of mental illness and treatment came to be based upon studies of chemicals in the urine, blood, and cerebrospinal fluid. The problem with this line of research was, and continues to be, a lack of consistent findings. Researchers have never been able to determine a "normal" baseline for comparing chemical concentrations in the brain.
The next phase of psychopharmacology research (1970s-1980s) saw the introduction of new technologies in molecular biology and radiology. This led scientists to distinguish the quality and quantity of cell membrane receptors in the brain. Medication effects came to be defined by receptor physiology and the behavioral effects of those interactions. Like chemical studies which came before it, the "receptor era" also failed to produce a reliable standard of reference point against which brain dysfunction could be identified.
Continuing advances in molecular biology and neuroimaging techniques transformed the focus of psychopharmacology research away from neurotransmitter levels, and away from receptor-ligand interactions on each brain cell, to the level of the genome. Since 1990, research has shifted increasingly to the analysis and manipulation of signal transduction, DNA transcription, and RNA translation within the neurons and glia. When a clinician and a patient exchange a prescription for a psychiatric drug today, they should both be thinking about the following questions:
How will this drug modify the expression of DNA, alter protein synthesis, and create changes in the function and structure of the brain cells?
How might these changes present a chronic stress to the human body? (page 51)
One final point about sensitization is worth emphasizing at this juncture. Although few physicians acknowledge the fact, there is considerable epidemiological and neuroscientific evidence to support the theory that psychiatric drugs sensitize the brain by altering neurotransmitter system reactivity and/or anatomic structures. Because these changes may exacerbate the physiological processes which mediate the symptoms of many conditions, all psychiatric drugs have the potential to prolong or worsen the disorders for which they are prescribed. (page 59)
It is quite likely that the inconsistencies which have plagued the field of psychiatric neuroimaging will continue indefinitely, either because the methods themselves are inherently unreliable (e.g., different investigators may be defining and measuring brain regions differently); or because the suppositions about the existence of radiographically identifiable and identical neuropathologies are, themselves, erroneous. (page 183)
With the possible exception of the chemotherapies used in the treatment of cancer, it would be difficult to identify a class of medications as toxic as the antipsychotics. Whether one considers the effects of dopamine antagonists upon the central nervous system or beyond, their proven harmfulness has been an iatrogenic tragedy too often minimized or denied. (page 214)