Haloperidol

Haloperidol - What is Haloperidol?

Haloperidol is a typical antipsychotic. It is in the butyrophenone class of antipsychotic medications and has pharmacological effects similar to the phenothiazines.

Haloperidol is an older antipsychotic used in the treatment of schizophrenia and, more acutely, in the treatment of acute psychotic states and delirium. A long-acting decanoate ester is used as a long acting injection given every 4 weeks to people with schizophrenia or related illnesses who have a poor compliance with medication and suffer frequent relapses of illness, or to overcome the drawbacks inherent to its orally administered counterpart that burst dosage increases risk or intensity of side effects. In some countries this can be involuntary under Community Treatment Orders.

Haloperidol is sold under the tradenames Aloperidin, Bioperidolo, Brotopon, Dozic, Duraperidol (Germany), Einalon S, Eukystol, Haldol, Halosten, Keselan, Linton, Peluces, Serenace, Serenase, and Sigaperidol. In medical slang, haloperidol is occasionally called vitamin H.

Haloperidol was discovered by Paul Janssen. It was developed in 1958 by the Belgian company Janssen Pharmaceutica and submitted to first clinical trials in Belgium in the same year. After being rejected by U.S. company Searle due to side effects, it was later marketed in the U.S. by McNeil Laboratories. It was approved by the U.S. Food and Drug Administration on April 12, 1967.

A comprehensive review of haloperidol has found it to be an effective agent in treatment of symptoms associated with schizophrenia.

Haloperidol is also used in the control of the symptoms of:

  • Acute psychosis, such as drug psychosis (LSD, psilocybin, amphetamines, ketamine, and phencyclidine), psychosis associated with high fever or metabolic disease
  • Acute manic phases until the concomitantly given first-line drugs such as lithium or valproate are effective
  • Hyperactivity, aggression.
  • Acute delirium
  • Otherwise uncontrollable severe behavioral disorders in children and adolescents
  • Agitation and confusion associated with cerebral sclerosis
  • Adjunctive treatment of alcohol and opioid withdrawal
  • Treatment of neurological disorders such as tic disorders, Tourette syndrome, and chorea
  • Treatment of severe nausea/emesis (postoperative, side-effects of radiation and cancer chemotherapy)
  • Adjunctive treatment of severe chronic pain, always together with analgesics
  • Therapeutic trial in personality disorders such as borderline personality disorder
  • Also used in the treatment of intractable hiccups

Some weeks or even months of treatment may be needed before a remission of schizophrenia is evident.

In some clinics the use of atypical neuroleptics (e.g. clozapine, risperidone, olanzapine, ziprasidone) is generally preferred over haloperidol, because these drugs have an appreciably lower incidence of extrapyramidal side-effects. Each of these drugs, however, has its own spectrum of potentially serious side-effects (e.g. agranulocytosis with clozapine, weight gain with increased risk of diabetes and of stroke). Atypical neuroleptics are also much more expensive and have recently been the subject of increasing controversy regarding their efficacy in comparison to older products and side effects.

Haloperidol was considered indispensable for treating psychiatric emergency situations, although the newer atypical drugs have gained greater role in a number of situations as outlined in a series of consensus reviews published between 2001 and 2005. It is enrolled in the World Health Organization List of Essential Medicines.

As is common with typical neuroleptics, haloperidol is by far more active against "positive" psychotic symptoms (delusions, hallucinations etc.) than against "negative" symptoms (social withdrawal, autism etc.). With the exception of the highly effective clozapine, the effectiveness of haloperidol against positive symptoms has not been outperformed by newer antipsychotics.

A multi-year UK study by the Alzheimer's Research Trust suggested that this and other neuroleptic anti-psychotic drugs commonly given to Alzheimer's patients with mild behavioural problems often make their condition worse. The study concluded that

Controversial non-medical uses

There are multiple reports from Soviet dissidents, including medical staff, on the use of haloperidol in the Soviet Union for punitive purposes or simply to break the prisoners' will. Notable dissidents that were administered haloperidol as part of their court ordered treatment were Sergei Kovalev and Leonid Plyushch. The accounts of Plyushch in the West, after he was allowed to leave the Soviet Union in 1976, were instrumental in the triggering Western condemnation of Soviet practices at the World Psychiatric Association's 1977 meeting. The use of haloperidol in the Soviet Union's psychiatric system was prevalent because it was one of the few psychotropic drugs produced in quantity in the USSR.

Haloperidol has been used for its sedating effects during the deportations of aliens by the United States Immigration and Customs Enforcement (ICE). During 2002-2008, federal immigration personnel used haloperidol to sedate 356 deportees. By 2008, followed court challenges over the practice, haloperidol was given to only 3 detainees. Following lawsuits, U.S. officials changed the procedure so that it is done only by the recommendation of medical personnel and under court order.

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Haloperidol Pharmacology

Haloperidol is a neuroleptic and a butyrophenone. Due to its strong central antidopaminergic action, it is classified as a highly potent neuroleptic. It is approximately 50 times more potent than chlorpromazine (sold under the brand name Thorazine, among others) on a weight basis (50 mg chlorpromazine is equivalent to 1 mg haloperidol).

Haloperidol possesses a strong activity against delusions and hallucinations, most likely due to an effective dopaminergic receptor blockage in the mesocortex and the limbic system of the brain. It blocks the dopaminergic action in the nigrostriatal pathways, which is the probable reason for the high frequency of extrapyramidal-motoric side-effects (dystonias, akathisia, pseudoparkinsonism). It has minor antihistaminic and anticholinergic properties, therefore cardiovascular and anticholinergic side-effects such as hypotension, dry mouth, constipation, etc., are seen quite infrequently, compared with less potent neuroleptics such as chlorpromazine.

Haloperidol also has sedative properties and displays a strong action against psychomotor agitation due to a specific action in the limbic system. However, in some cases Haloperidol may worsen psychomotor agitation via its potent Dopamine receptor antagonism. Dopamine receptor antagonism, notably of the D2 receptor subtype, can cause akathisia, psychomotor agitation, anxiety, and restlessness, which may worsen the condition of some patients.

The peripheral antidopaminergic effects of haloperidol account for its strong antiemetic activity. There, it acts at the chemoreceptor trigger zone (CTZ). Haloperidol is useful to treat severe forms of nausea/emesis such as those resulting from chemotherapy. The peripheral effects lead also to a relaxation of the gastric sphincter muscle and an increased release of the hormone prolactin, with the possible emergence of breast enlargement and secretion of milk (galactorrhea) in both sexes.

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Haloperidol Pharmacokinetics

Intramuscular injections

The drug is well and rapidly absorbed and has a high bioavailability. Plasma-levels reach their maximum within 20 minutes after injection. The decanoate injectable formulation is for intramuscular administration only and should never be used intravenously.

Intravenous injections

The bioavailability is 100% and the very rapid onset of action is seen within about ten minutes. The duration of action is 3 to 6 hours. If haloperidol is given as a slow IV infusion, the onset of action is slowed, but the duration prolonged compared to IM injection.

Therapeutic concentrations

Plasma levels of 4 to 25 micrograms per liter are required for therapeutic action. The determination of plasma levels can be used to calculate dose adjustments and to check compliance, particularly in long-term patients. Plasma levels in excess of the therapeutic range may lead to a higher incidence of side-effects or even pose the risk of haloperidol intoxication.

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Haloperidol Contraindications

Absolute

  • Preexisting coma, acute stroke
  • Severe intoxication with alcohol or other central depressant drugs
  • Known allergy against haloperidol or other butyrophenones or other drug ingredients
  • Known heart disease; when combined will tend towards cardiac arrest

Special caution needed

  • Preexisting Parkinson's disease
  • Patients at special risk for the development of QT prolongation (hypokalemia, concomitant use of other drugs causing QT prolongation)
  • Compromised liver-function (as haloperidol is metabolized and eliminated mainly by the liver, dose reductions and/or spaced intervals may be needed)
  • Haloperidol may decrease the seizure-threshold. Treat patients with epilepsy and those with risk factors for the development of seizures (alcohol withdrawal, encephalopathy) with caution. Maintain existing anticonvulsive therapy.
  • Patients with hyperthyreosis; the action of haloperidol is intensified and side-effects are more likely. Initiate an effective therapy of hyperthyreosis.
  • IV injections: inject slowly to avoid hypotension or orthostatic collapse. Avoid IV injections in cardiovascular unstable patients (preexisting hypotension, shock, concomitant antihypertensive therapy, heart insufficiency). Prefer in these cases moderate oral or IM doses.

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Haloperidol Drug Interactions

  • Other central depressants (alcohol, tranquilizers, narcotics): actions and side-effects of these drugs (sedation, respiratory depression) are increased. In particular, the doses of concomitantly used opioids for chronic pain can be reduced by 50%.
  • Methyldopa: increased risk of extrapyramidal side-effects and other unwanted central effects
  • Levodopa: decreased action of levodopa
  • Tricyclic antidepressants: metabolism and elimination of tricyclics significantly decreased, increased toxicity noted (anticholinergic and cardiovascular side-effects, lowering of seizure-threshold)
  • Quinidine, buspirone, and fluoxetine: increased plasma-levels of haloperidol, decrease haloperidol dose, if necessary
  • Carbamazepine, phenobarbital, and rifampicin: plasma-levels of haloperidol significantly decreased, increase haloperidol dose, if necessary.
  • lithium: rare cases of the following symptoms have been noted: encephalopathy, early and late extrapyramidal side-effects, other neurologic symptoms and coma. Check lithium plasma levels regularly and keep the dose of haloperidol as low as possible.
  • Guanethidine: antihypertensive action antagonized
  • Epinephrine: action antagonized, paradoxical decrease in blood pressure may result

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Haloperidol Overdose

Experimental evidence from animal studies indicates that doses needed for acute poisoning are quite high in relation to therapeutic doses.

Overdoses with depot injections are uncommon, because only certified personnel are legally permitted to administer them to patients.

Symptoms

Symptoms are usually due to exaggerated side-effects. Most often encountered are:

  • Severe extrapyramidal side-effects with muscle rigidity and tremors, akathisia etc. (inject 5 mg biperiden (Akineton) slowly IV, repeat after some hours if necessary). Sometimes oral or IM treatment with biperiden is needed for several days or even weeks. If the patient is very upset about extrapyramidal side-effects, small doses of lorazepam (0.5 to 1 mg orally, repeated every 4 to 6 hours if necessary) can be given. Lorazepam has an intrinsic action against upset, anxiety, and extrapyramidal side-effects.
  • Hypotension or hypertension
  • Sedation
  • Anticholinergic side-effects (dry mouth, constipation, paralytic ileus, difficulties in urinating, massive sweating). Cautious doses of physostigmine may be given repeatedly. Physostigmine may increase the risk of seizures.
  • Coma in severe cases, accompanied by respiratory depression and massive hypotension, shock
  • Rarely serious ventricular arrhythmia (torsades de pointes) with or without prolonged QT-time
  • Epileptic seizures, give careful doses of diazepam 5 mg to 10 mg by slow IV injection, repeatedly if needed, until seizures subside. Take care not to worsen central depression or respiratory depression caused by haloperidol. The treatment facility should be able to institute artificial respiration readily. Valproate first given as slow IV infusion and later orally may also be effective.

Treatment

Treatment is merely symptomatic and involves intensive care with stabilization of vital functions. In early detected cases of oral overdose induction of emesis, gastric lavage and the use of activated charcoal can all be tried. Avoid epinephrine for treatment of hypotension and shock, because its action might be reversed.

Prognosis

Generally, the prognosis of overdose is good and lasting damage is not known, provided that the patient has survived the initial phase.

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Haloperidol and Pregnancy

Data from animal experiments indicate haloperidol is not teratogenic, but is embryotoxic in high doses. In humans, no controlled studies exist.

Unconfirmed studies in pregnant women revealed possible damage to the fetus, although most of the women were exposed to multiple drugs during pregnancy.

Following accepted general principles, haloperidol should only be given during pregnancy if the benefit to the mother clearly outweighs the potential fetal risk.

Haloperidol, when given to lactating women, is found in significant amounts in their milk. Breastfed children sometimes show extrapyramidal symptoms. If the use of haloperidol during lactation seems indicated, the benefit for the mother should clearly outweigh the risk for the child. Consider termination of breastfeeding.

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