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 dose of HALDOL Decanoate 50 or HALDOL Decanoate 100 should be expressed in terms of its haloperidol content. The starting dose of haloperidol decanoate should be based on the patient's age, clinical history, physical condition, and response to previous antipsychotic therapy. The preferred approach to determining the minimum effective dose is to begin with lower initial doses and to adjust the dose upward as needed. For patients previously maintained on low doses of antipsychotics (. up to the equivalent of 10 mg/day oral haloperidol), it is recommended that the initial dose of haloperidol decanoate be 10–15 times the previous daily dose in oral haloperidol equivalents; limited clinical experience suggests that lower initial doses may be adequate.
Haldol is available in sterile vials containing 5 mg strength Haldol per 1 ml of fluid used for injection. Usual starting dose is -5 mg intramuscularly. Dose may vary according to patient response to the drug. Switch to an oral form of this drug is recommended as soon as possible. Haldol may interact with other drugs so the patient needs close observation or monitoring to determine if other side effects develop. Haldol should only be used during pregnancy or in women likely to become pregnant only if the benefit clearly justifies a potential risk to the fetus; fetal abnormalities and fetal exposure to Haldol in the third trimester have shown dependence at birth. Women who are breastfeeding should not take Haldol because the drug may affect the infant. Although reports of use for behavior modification exist, the drug is not approved for use in children.