The specific features of a patient's clinical condition,
the underlying cause(s) of the delirium, and associated conditions
may be used by the psychiatrist to determine the choice of specific
somatic therapy. Antipsychotic medications are the pharmacologic
treatment of choice in most cases of delirium because of their efficacy
in the treatment of psychotic symptoms. Haloperidol is most frequently
used because of its short half-life, few or no anticholinergic side
effects, no active metabolites, and lower likelihood of causing
sedation. Haloperidol may be administered orally or intramuscularly,
but it appears to cause fewer extrapyramidal side effects when administered intravenously.
An optimal dose range for patients with delirium has not been determined.
Initial doses of haloperidol in the range of 1–2 mg every
2–4 hours as needed have been used, and even lower starting
doses (e.g., 0.25–0.50 mg every 4 hours as needed) are
suggested for elderly patients. Titration to higher doses may be
required for patients who continue to be agitated. Although total daily
intravenous doses in the hundreds of milligrams have been given
under closely monitored conditions, much lower doses usually suffice.
Continuous intravenous infusions of antipsychotic medications can
be used for patients who have required multiple bolus doses of antipsychotic medications.
Initiating haloperidol with a bolus dose of 10 mg followed by continuous
intravenous infusion of 5–10 mg/hour has been
suggested. Droperidol, either alone or followed by haloperidol, can
be considered for patients with delirium and acute agitation for
whom a more rapid onset of action is required. The ECG should be
monitored in patients receiving antipsychotic medications for delirium,
and a QTc interval longer than 450 msec or more than 25% over
baseline may warrant a cardiology consultation and consideration
of discontinuation of the antipsychotic medication. The availability
of new antipsychotic medications (risperidone, olanzapine, and quetiapine)
with their different side effect profiles has led some physicians
to use these agents for the treatment of delirium.