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 .
Drug has few CV adverse effects and may be preferred in patients with cardiac disease.
Dose of 2 mg is therapeutic equivalent of 100 mg chlorpromazine.
When changing from tablets to decanoate injection, patient should initially receive 10 to 20 times the oral dose once monthly (not more than 100 mg).
Assess patient periodically for extrapyramidal reactions and tardive dyskinesia.
Don’t withdraw drug abruptly except when required, because abrupt withdrawal may cause severe adverse reaction. Taper dosage over several weeks.
Safety and efficacy of drug injection in children haven’t been established, and oral drug isn’t recommended for children younger than age 3.
Drug is especially useful for agitation related to senile dementia. Tardive dyskinesia may occur more often, especially in elderly women.
Elderly patients usually need lower initial doses and a more gradual dosage adjustment.