Bh. Harvey et al., The new-generation antipsychotics - Integrating the neuropathology and pharmacology of schizophrenia, S AFR MED J, 89(6), 1999, pp. 661-672
Despite a well-established role for dopamine (DA) in the neuropathology of
schizophrenia, and the evidence of a hyperdopaminergic state in the schizop
hrenic brain, many questions still remain. Typical agents acting predominan
tly on DA D-2 receptors are only partially effective. New data now indicate
that the interaction between DA and the various DA receptors as well as DA
interaction with other transmitter systems, are more critical in deciding
the therapeutic success of an antipsychotic than actions on DA alone. These
interactions are closely associated with what is being documented regardin
g the neuro-anatomy, neurobiology and neuropsychology of the disorder.
There have been major advances in the understanding of the neuropathology o
f schizophrenia that, while not replacing the original DA hypothesis, have
forced a re-evaluation of our understanding of the disorder. In this paper
we present the biochemical and neuropathological basis for schizophrenia an
d discuss six new atypical antipsychotics according to these theories. Drug
s reviewed include clozapine, risperidone, olanzapine, ziprasidone, sertind
ole and quetiapine.
While not a comparative analysis of these drugs, this paper is an appraisal
of how their pharmacology correlates with our present knowledge of the dis
order and highlights differences among the drugs in this group. These agent
s therefore possess specifically designed qualities, to varying degrees, pr
omising a significant improvement over earlier agents in terms of treating
positive and negative symptoms, with a minimal risk of extrapyramidal, symp
toms (EPS). These qualities include an emphasis on D-2 selectivity, D-1/D-2
balance, DA/serotonin (5HT) balance, D-3/D-4 selectivity, DA/acetylcholine
(Ach) balance and glutamate (Glu)/gamma-aminobutyric acid (GABA) balance.
The drugs are discussed with reference to these criteria.
Targeted drug design has created a goal-directed strategy with which to tre
at schizophrenia. These new antipsychotics appear to have several distinct
advantages over their predecessors, and should make a major contribution to
the treatment of schizophrenia and the re-integration of these patients in
to society.