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.
Pre-excitation syndrome is a heart condition in which part of the cardiac ventricles are activated too early. Pre-excitation is caused by an abnormal electrical connection or accessory pathway between or within the cardiac chambers. Pre-excitation may not cause any symptoms but may lead to palpitations caused by abnormal heart rhythms. It is usually diagnosed using an electrocardiogram, but may only be found during an electrophysiological study. The condition may not require any treatment at all, but symptoms can be controlled using medication or catheter ablation. Types
Several types of pre-excitation syndrome have been described. Pathophysiology
Normally, the atria and the ventricles are electrically isolated, and electrical contact between them exists only at the "atrioventricular node". In all pre-excitation syndromes, at least one more conductive pathway is present. Physiologically, the normal electrical depolarization wave is delayed at the atrioventricular node to allow the atria to contract before the ventricles. However, there is no such delay in the abnormal pathway, so the electrical stimulus passes to the ventricle by this tract faster than via normal atrioventricular/bundle of His system, and the ventricles are depolarized (excited) before (pre-) normal conduction system. References


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