In the wake of the black-box warning, Ethan Cumbler, MD, a hospitalist and director of the acute care for the elderly (ACE) service at the University of Colorado Hospital, began noticing that the drug was still being used throughout the hospital, sometimes even in the ACE unit. He and some colleagues began investigating how often IV haloperidol was being ordered “and whether those orders complied with expert recommendations for ECG monitoring. Their results were published in the January 2013 issue of the Journal of the American Geriatrics Society.
Haloperidol is a typical butyrophenone type antipsychotic that exhibits high affinity dopamine D 2 receptor antagonism and slow receptor dissociation kinetics.  It has effects similar to the phenothiazines .  The drug binds preferentially to D 2 and α 1 receptors at low dose (ED 50 = and mg/kg, respectively), and 5-HT 2 receptors at a higher dose (ED 50 = mg/kg). Given that antagonism of D 2 receptors is more beneficial on the positive symptoms of schizophrenia and antagonism of 5-HT 2 receptors on the negative symptoms, this characteristic underlies haloperidol's greater effect on delusions, hallucinations and other manifestations of psychosis.  Haloperidol's negligible affinity for histamine H 1 receptors and muscarinic M 1 acetylcholine receptors yields an antipsychotic with a lower incidence of sedation, weight gain, and orthostatic hypotension though having higher rates of treatment emergent extrapyramidal symptoms .