Patients with schizophrenia display disordered thinking,
withdrawal, paranoid delusions, and auditory hallucinations. This disorder is
thought to be related to an excess of dopaminergic activity in the brain.
The most commonly used antipsychotics
include phenothiazines, thioxanthenes, phenylbu-tylpiperadines,
dihydroindolones, dibenzapines, benzisoxazoles, and butyrophenones. There are
numerous trade names for these drugs. Older anti-psychotic medications had
strong dopamine antago-nistic effects, leading to extrapyramidal side effects
(eg, muscle rigidity and progression to tardive dyski-nesia). Other agents have
less dopamine antagonism and occupy the D2 dopamine receptor to a lesser
degree, thereby reducing extrapyramidal effects. The antipsychotic effect of
these agents seems to be due to dopamine antagonist activity. Most are sedating
and mildly anxiolytic. Mild α-adrenergic block-ade and
anticholinergic activity are also observed. Side effects include orthostatic
hypotension, acute dystonic reactions, and parkinsonism-like mani-festations.
Risperidone and clozapine have little extrapyramidal activity, but the latter
is associated with a significant incidence of granulocytopenia. T-wave
flattening, ST segment depression, and pro-longation of the PR and QT intervals
may be seen, increasing the risk of les torsades des pointes.
Continuing antipsychotic medication periop-eratively is
desirable. Reduced anesthetic require-ments may be observed in some patients,
and some patients may experience perioperative hypotension.