The depot forms are not suitable for initial treatment, but are suitable for patients who have demonstrated inconsistency with oral dosages.The decanoate ester of haloperidol (haloperidol decanoate, trade names Haldol decanoate, Halomonth, Neoperidole) has a much longer duration of action, so is often used in people known to be noncompliant with oral medication. A dose is given by intramuscular injection once every two to four weeks. The IUPAC name of haloperidol decanoate is [4-(4-chlorophenyl)-1-[4-(4-fluorophenyl)-4-oxobutyl]piperidin-4-yl] decanoate. Topical formulations of haloperidol should not be used as treatment for nausea because research does not indicate this therapy is more effective than alternatives. Adverse effects
Sources for the following lists of adverse effects:As haloperidol is a high-potency typical antipsychotic, it tends to produce significant extrapyramidal side effects. According to a 2013 meta-analysis of the comparative efficacy and tolerability of 15 antipsychotic drugs it was the most prone of the 15 for causing extrapyramidal side effects.With more than 6 months of use 14 percent of users gain weight. Haloperidol may be neurotoxic.Common (>1% incidence)

Extrapyramidal side effects including:
Akathisia (motor restlessness)
Dystonia (continuous spasms and muscle contractions)
Muscle rigidity
Parkinsonism (characteristic symptoms such as rigidity)
Hypotension
Anticholinergic side effects such as: (These adverse effects are less common than with lower-potency typical antipsychotics, such as chlorpromazine and thioridazine.) Blurred vision
Constipation
Dry mouth
Somnolence (which is not a particularly prominent side effect, as is supported by the results of the aforementioned meta-analysis.
Haloperidol, sold under the brand name Haldol among others, is a typical antipsychotic medication. Haloperidol is used in the treatment of schizophrenia, tics in Tourette syndrome, mania in bipolar disorder, delirium, agitation, acute psychosis, and hallucinations from alcohol withdrawal. It may be used by mouth or injection into a muscle or a vein. Haloperidol typically works within 30 to 60 minutes. A long-acting formulation may be used as an injection every four weeks by people with schizophrenia or related illnesses, who either forget or refuse to take the medication by mouth.Haloperidol may result in a movement disorder known as tardive dyskinesia which may be permanent. Neuroleptic malignant syndrome and QT interval prolongation may occur. In older people with psychosis due to dementia it results in an increased risk of death. When taken during pregnancy it may result in problems in the infant. It should not be used by people with Parkinsons disease.Haloperidol was discovered in 1958 by Paul Janssen, prepared as part of a structure-activity relationship investigation into analogs of pethidine (meperidine). It is on the World Health Organizations List of Essential Medicines. It is the most commonly used typical antipsychotic. In 2017, it was the 296th most commonly prescribed medication in the United States, with more than one million prescriptions. Medical uses
Haloperidol is used in the control of the symptoms of:

Acute psychosis, such as drug-induced psychosis caused by, amphetamines, ketamine, and phencyclidine, and psychosis associated with high fever or metabolic disease. Some evidence, however, has found haloperidol to worsen psychosis due to psilocybin.