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 .
The intravenous route is not FDA approved and is generally not recommended except when no other alternatives are available. Intravenous administration appears to be associated with a higher risk of QT prolongation and torsade de pointes (TdP) than other forms of administration. The manufacturer recommends ECG monitoring for QT prolongation and arrhythmias if IV administration is required. A dose in the range of 1 to 5 mg IV has been suggested, with the dose being repeated at 30 to 60 minute intervals, if needed. A maximum IV dose has not been established. The lowest effective dose should be used in conjunction with conversion to oral therapy as soon as possible.
It should not be used concomitantly with medications known to prolong the QTc interval (. 5-HT3 antagonists , tricyclic antidepressants , citalopram , etc.) as this may lead to an increased risk of QTc interval prolongation.   Neither should it be given concurrently with lithium (medication) as it may increase the risk of lithium toxicity and neuroleptic malignant syndrome .    It should not be given concurrently with other antipsychotics due to the potential for this to increase the risk of side effects, especially neurological side effects such as neuroleptic malignant syndrome .    It should be avoided in patients on CNS depressants such as opioids, alcohol and barbiturates.