Haloperidol

Absorption

Haloperidol is a highly lipophilic compound and is extensively metabolized in humans, which may cause a large interindividual variability in its pharmacokinetics.
Studies have found a wide variance in pharmacokinetic values for orally administered haloperidol with 1.7-6.1 hours reported for time to peak plasma concentration (tmax), 14.5-36.7 hours reported for half-life (t1?2), and 43.73 μg/L?h [range 14.89-120.96 μg/L?h] reported for AUC. Haloperidol is well-absorbed from the gastrointestinal tract when ingested orally, however, the first-pass hepatic metabolism decreases its oral bioavailability to 40 - 75%.
After intramuscular administration, the time to peak plasma concentration (tmax) is 20 minutes in healthy individuals or 33.8 minutes in patients with schizophrenia, with a mean half-life of 20.7 hours. Bioavailability following intramuscular administration is higher than that for oral administration.
Administration of haloperidol decanoate (the depot form of haloperidol for long-term treatment) in sesame oil results in slow release of the drug for long-term effects. The plasma concentrations of haloperidol gradually rise, reaching its peak concentration at about 6 days after the injection, with an apparent half-life of about 21 days. Steady-state plasma concentrations are achieved after the third or fourth dose.

Toxicity

Acute oral toxicity (LD50): 71 mg/kg in rats .

Description

Haloperidol is a venerable antipsychotic drug that is used to treat schizophrenia, Tourette syndrome, bipolar disorder, and other conditions.
Paul A. J. Janssen at Janssen Pharmaceutica (Beerse, Belgium), discovered haloperidol in the mid-1950s. Clinical trials began in 1958, but the US Food and Drug Administration did not approve the medicine until 1967. It was first marketed by McNeil Laboratories (Fort Washington, PA) under the trade name Haldol.
Haloperidol has many side effects, some of them serious; but it is still a widely used medication. In 2018, Kristen Brennand and colleagues at the Icahn School of Medicine at Mount Sinai Hospital (New York City) and Eli Lilly (Indianapolis) used haloperidol and 134 other drugs (not all of them antipsychotics) to develop a new screening method for schizophrenia drugs. Their impetus was that as many as 30% of schizophrenia patients are unresponsive to existing drugs, and current drug screens are not effective.
The researchers gathered skin cells from 24 individuals, 12 with schizophrenia and 12 controls. They converted those cells to stem cells and then to neural progenitor cells. When the scientists exposed the neural cells to the test drugs, the cells derived from schizophrenia patients showed sharper disease-related gene expression responses to antipsychotics than did the cells from the control studies.
This proof-of-concept experiment revealed the possibility of using similar screening methods to evaluate potential anti-schizophrenia drugs. The authors also suggest that a patient’s own cells might be used to determine which medicines are most effective against that individual’s disease.

Description

Haloperidol is a butyrophenone with a long duration of action. It has lile α- adrenoceptor blocking activity and minimal effect on the cardiovascular system. It is an effective antiemetic but has a high incidence of extrapyramidal adverse effects. Haloperidol may be used in the short-term management of the acutely agitated patient (when sinister causes of confusion such as hypoxaemia and sepsis have been excluded) and in the management of delirium in ICU. The duration of action of haloperidol is approximately 24–48h.

Chemical properties

White Crystalline Powder

Originator

Haldol,Janssen-Le Brun,France,1960

The Uses of Haloperidol

Haloperidol has been used:

• in ethanol to serves as an inhibitor of Erg2p
• to address the mechanism of haloperidol in ferroptosis using hepatocellular carcinoma cells: Hep G2 and Huh-7 cell lines
• in receptor internalization assay
• as an antipsychotic drug in Dulbecco′s Modified Eagle medium

The Uses of Haloperidol

Antidyskinetic; antipsychotic

The Uses of Haloperidol

Haloperidol is one of the most actively used modern neuroleptics. Its high antipsychotic activity is combined with a moderate sedative effect. It effectively stops various types of psychomotor excitement. It is used for schizophrenic psychoses, manic, paranoid, and delirious conditions, depression, psychomotor excitement of various origins, and for delirium and hallucinations of different origin.

Background

Haloperidol is a high potency first-generation (typical) antipsychotic and one of the most frequently used antipsychotic medications used worldwide. While haloperidol has demonstrated pharmacologic activity at a number of receptors in the brain, it exerts its antipsychotic effect through its strong antagonism of the dopamine receptor (mainly D2), particularly within the mesolimbic and mesocortical systems of the brain. Haloperidol is indicated for the treatment of the manifestations of several psychotic disorders including schizophrenia, acute psychosis, Tourette syndrome, and other severe behavioural states. It is also used off-label for the management of chorea associated with Huntington's disease and for the treatment of intractable hiccups as it is a potent antiemetic. Dopamine-antagonizing medications such as haloperidol are though to improve psychotic symptoms and states that are caused by an over-production of dopamine, such as schizophrenia, which is theorized to be caused by a hyperdopaminergic state within the limbic system of the brain.
Use of the first-generation antipsychotics (including haloperidol) is considered highly effective for the management of the "positive" symptoms of schizophrenia including hallucinations, hearing voices, aggression/hostility, disorganized speech, and psychomotor agitation. However, this class of drugs is also limited by the development of movement disorders induced by dopamine-blockade such as drug-induced parkinsonism, akathisia, dystonia, tardive dyskinesia, as well as other side effects including sedation, weight gain, and prolactin changes. While there are limited high-quality studies comparing haloperidol to lower-potency first-generation antipsychotics such as Chlorpromazine, Zuclopenthixol, Fluphenazine, and Methotrimeprazine, haloperidol typically demonstrates the least amount of side effects within this class, but demonstrates a stronger disposition for causing extrapyramidal symptoms (EPS). These other low‐potency antipsychotics are limited by their lower affinity for dopamine receptors, which requires a higher dose to effectively treat symptoms of schizophrenia. In addition, they block many receptors other than the primary target (dopamine receptors), such as cholinergic or histaminergic receptors, resulting in a higher incidence of side effects such as sedation, weight gain, and hypotension.
Interestingly, in vivo pharmacogenetic studies have demonstrated that the metabolism of haloperidol may be modulated by genetically determined polymorphic CYP2D6 activity. However, these findings contradict the findings from studies in vitro with human liver microsomes and from drug interaction studies in vivo. Inter-ethnic and pharmacogenetic differences in haloperidol metabolism may possibly explain these observations.
First-generation antipsychotic drugs have largely been replaced with second- and third-generation (atypical) antipsychotics such as Risperidone, Olanzapine, Clozapine, Quetiapine, Aripiprazole, and Ziprasidone. However, haloperidol use remains widespread and is considered the benchmark for comparison in trials of the newer generation antipsychotics.
The efficacy of haloperidol was first established in controlled trials in the 1960s.

Indications

Haloperidol is indicated for a number of conditions including for the treatment of schizophrenia, for the manifestations of psychotic disorders, for the control of tics and vocal utterances of Tourette’s Disorder in children and adults, for treatment of severe behavior problems in children of combative, explosive hyperexcitability (which cannot be accounted for by immediate provocation). Haloperidol is also indicated in the short-term treatment of hyperactive children who show excessive motor activity with accompanying conduct disorders consisting of some or all of the following symptoms: impulsivity, difficulty sustaining attention, aggressivity, mood lability, and poor frustration tolerance. Haloperidol should be reserved for these two groups of children only after failure to respond to psychotherapy or medications other than antipsychotics.

Definition

ChEBI: A compound composed of a central piperidine structure with hydroxy and p-chlorophenyl substituents at position 4 and an N-linked p-fluorobutyrophenone moiety.

Manufacturing Process

A stirred slurry of 120.0 parts 4-(4-chlorophenyl)-piperidin-4-ol hydrochloride and 40.0 parts of potassium iodide in 500 parts of water is warmed to a temperature of about 35°C under a nitrogen atmosphere. Then, 70.0 parts of potassium hydroxide is added. After further heating to about 55°C. 138.0 parts of 1,1 dimethoxy-1-(4-fluorophenyl)-4-chlorobutane is added. The temperature is then raised to about 102°C and heating continued for 3.5 hours. After cooling to about 75°C. 785 parts of toluene is added to the reaction mixture and stirred for about 5 minutes. An additional 320 parts of toluene is added and the water and organic layers separated. 102 parts of methanol is used to rinse the flask and added to the organic layer to provide a solution of 4-(4-chlorophenyl)-1-[4-(4-fluorophenyl)-4,4-dimethoxybutyl]- piperidin-4-ol. Then, 59 parts of concentrated hydrochloric acid is added to a stirred solution of the organic layer to precipitate a solid. The solid is filtered, rinsed twice with 550 parts by volume portions of a 10:9:1 acetone-toluenemethanol mixture, twice with 400 parts by volume portions of a 10:l acetonemethanol mixture, and air-dried. The dried solid is then dissolved in 1,950 parts of methanol with gentle heating on a steam bath. The resulting solution is filtered and 300 parts by volume of concentrated ammonium hydroxide is added. Heating is continued to reflux and maintained thereat for about 1 hour.Then, 2,520 parts of water is added and the slurry stirred at about 75°C for 1.5 hours. After cooling to about 25°C. the solid is filtered, washed twice with 600 parts by volume portions of a 3:1 mixture of water-methanol, and airdried. The resulting product, 4-[4-chlorophenyl)-4-hydroxypiperidino]-4'- fluorobutyrophenone, is obtained in 32.5% yield. This product melts at about 148.5°C to 150.5°C.

brand name

Haldol (OrthoMcNeil).

Therapeutic Function

Antidyskinetic, Antipsychotic

General Description

Haloperidol, 4-[4-(p-chlorophenyl)-4-hydroxypiperidino]-4-fluorobutyrophenone (Haldol), is anodorless white to yellow crystalline powder. Haloperidol iswell and rapidly absorbed and has a high bioavailability. It ismore than 90% bound to plasma proteins. Haloperidol is excretedslowly in the urine and feces. About 30% of a dose isexcreted in urine and about 20% of a dose in feces via biliaryelimination,and only 1% of a dose is excreted as unchangeddrug in the urine.Haloperidol is a minor substrate of CYP1A2 and a major substrate of CYP2D6 and CYP3A4.CYP2D6 inhibitors may increase the levels/effects ofhaloperidol.Haloperidol may increase the levels/effects ofCYP2D6 substrates and it may decrease the bioactivationof CYP2D6 prodrugs substrates. Haloperidol also is a moderateinhibitor of CYP2D6 and CYP3A4. CYP3A4 inducersmay decrease the levels/effects of haloperidol, whereasCYP3A4 inhibitors may increase the levels/effects ofhaloperidol. Centrally acting acetylcholinesterase inhibitorsmay increase the risk of antipsychotic-related EPS. The precisemechanism of antipsychotic action is unclear but isconsidered to be associated with the potent DA D₂receptor–blocking activity in the mesolimbic system and theresulting adaptive changes in the brain. Haloperidol is usedprimarily for the long-term treatment of psychosis and is especiallyuseful in patients who are noncompliant with theirdrug treatment.

General Description

Haloperidol, 4[4-(p-chlorophenyl)-4-hydroxypiperidone]-4' -n-fluorobutyrophenone (Haldol),the representative of several related classes of aromaticbutylpiperidine derivatives, is a potent antipsychotic usefulin schizophrenia and in psychoses associated with braindamage. It is frequently chosen as the agent to terminatemania and often used in therapy for Gilles de la Tourettesyndrome. Haloperidol-induced dyskinesias may involveneurotoxicological metabolite similar to dopaminergic toxicantMPP⁺.

Pharmaceutical Applications

Haloperidol is an analogue of the dopamine D2 receptor antagonist and is an older antipsychotic drug. The drug is used in the treatment of schizophrenia, a neuropsychiatric disorder. In general, antipsychotic drugs work by blocking the dopamine D₂ receptors.
Haloperidol is such an antipsychotic drug, which was developed in the 1950s and entered the clinic soon after that. Its use is limited by the high incidence of extrapyramidal symptoms (movement disorders caused by drugs affecting the extrapyramidal system, a neural network which is part of the motor system). Nevertheless, haloperidol may be used for the rapid control of hyperactive psychotic states and is popular for treating restlessness in the elderly.

Biological Activity

Dopamine antagonist with selectivity for D 2 -like receptors (K i values are 1.2, ~ 7, 2.3, ~ 80 and ~ 100 nM for D 2 , D 3 , D 4 , D 1 and D 5 receptors respectively). Subtype-selective NMDA antagonist.

Biochem/physiol Actions

Haloperidol is a butyrophenone antipsychotic. It is also classified as a neuroleptic (powerful tranquilizer). Haloperidol acts as a D2, D3, and D4 dopamine receptor antagonist and thus causes Parkinson′s disorder. It also has a negative effect on the central nervous system.

Pharmacokinetics

Use of the first-generation antipsychotics (including haloperidol) is considered highly effective for the management of the "positive" symptoms of schizophrenia including hallucinations, hearing voices, aggression/hostility, disorganized speech, and psychomotor agitation. However, this class is limited by the development of movement disorders such as drug-induced parkinsonism, akathisia, dystonia, and tardive dyskinesia, and other side effects including sedation, weight gain, and prolactin changes. Compared to the lower-potency first-generation antipsychotics such as Chlorpromazine, Zuclopenthixol, Fluphenazine, and Methotrimeprazine, haloperidol typically demonstrates the least amount of side effects within class, but demonstrates a stronger disposition for causing extrapyramidal symptoms (EPS). Low‐potency medications have a lower affinity for dopamine receptors so that a higher dose is required to effectively treat symptoms of schizophrenia. In addition, they block many receptors other than the primary target (dopamine receptors), such as cholinergic or histaminergic receptors, resulting in a higher incidence of side effects such as sedation, weight gain, and hypotension.
The balance between the wanted drug effects on psychotic symptoms and unwanted side effects are largely at play within dopaminergic brain pathways affected by haloperidol. Cortical dopamine-D2-pathways play an important role in regulating these effects and include the nigrostriatal pathway, which is responsible for causing extrapyramidal symptoms (EPS), the mesolimbic and mesocortical pathways, which are responsible for the improvement in positive schizophrenic symptoms, and the tuberoinfundibular dopamine pathway, which is responsible for hyperprolactinemia.
A syndrome consisting of potentially irreversible, involuntary, dyskinetic movements may develop in patients. Although the prevalence of the syndrome appears to be highest among the elderly, especially elderly women, it is impossible to rely upon prevalence estimates to predict, at the inception of antipsychotic treatment, which patients are likely to develop the syndrome.
Cases of sudden death, QT-prolongation, and Torsades de Pointes have been reported in patients receiving haloperidol. Higher than recommended doses of any formulation and intravenous administration of haloperidol appear to be associated with a higher risk of QT-prolongation and Torsades de Pointes. Although cases have been reported even in the absence of predisposing factors, particular caution is advised in treating patients with other QT-prolonging conditions (including electrolyte imbalance [particularly hypokalemia and hypomagnesemia], drugs known to prolong QT, underlying cardiac abnormalities, hypothyroidism, and familial long QT-syndrome).
A potentially fatal symptom complex sometimes referred to as Neuroleptic Malignant Syndrome (NMS) has been reported in association with antipsychotic drugs. Clinical manifestations of NMS are hyperpyrexia, muscle rigidity, altered mental status (including catatonic signs) and evidence of autonomic instability (irregular pulse or blood pressure, tachycardia, diaphoresis, and cardiac dysrhythmias). Additional signs may include elevated creatine phosphokinase, myoglobinuria (rhabdomyolysis) and acute renal failure.

Clinical Use

Sedative in severe anxiety
Intractable hiccup
Motor tics
Nausea and vomiting
Schizophrenia and other psychoses

Synthesis

Haloperidol, 4-[4-(p-chlorophenyl)-4-hydroxypiperidino]-4??-fluorobutyrophenone (6.3.8), is synthesized by the alkylation of 4-(4-chlorophenyl)-4-hydroxypiperidine (6.3.7) using 4??-chloro-4-fluorobutyrophenone (6.3.4). 4-(4-Chlorophenyl) -4-hydroxypiperidine (6.3.7) is synthesized from 2-(4-chlorophenyl)propene, which on reaction with formaldehyde and ammonium chloride gives the intermediate 4-methyl-4-(4-chlorophenyl)-1, 3-oxazine (6.3.5), evidently through stages postulated for the Prince reaction. Treatment of the resulting product with hydrochloric acid leads to the formation of 4-(4-chlorophenyl)-1,2,3,6- tetrahydropiperidine (6.3.6), probably through a stage of opening of the hydrogenated 1,3-oxazine ring, followed by dehydration, and subsequent recyclization. Addition of hydrogen bromide to the double bond of 4-(4-chlorophenyl)1,2,3,6-tetrahydropipidine (6.3.6) and the subsequent alkaline hydrolysis of the 4-(4-chlorophenyl)-4-bromopiperidine formed during the reaction, gives 4-(4-chlorophenyl)-4-hydroxypiperidine (6.3.7), the reaction of which with 4??-chloro-4-fluorobutyrophenone (6.3.4) gives the desired haloperidol (6.3.6) [41¨C46].

Drug interactions

Potentially hazardous interactions with other drugs
Anaesthetics: enhanced hypotensive effects.
Analgesics: increased risk of convulsions with tramadol; enhanced hypotensive and sedative effects with opioids; possibly severe drowsiness with indometacin or acemetacin; increased risk of ventricular arrhythmias with methadone.
Anti-arrhythmics: increased risk of ventricular arrhythmias with anti-arrhythmics that prolong the QT interval; increased risk of ventricular arrhythmias with amiodarone or disopyramide - avoid.
Antibacterials: increased risk of ventricular arrhythmias with moxifloxacin and delamanid - avoid with moxifloxacin; concentration reduced by rifampicin.
Antidepressants: increased risk of ventricular arrhythmias with citalopram, escitalopram and tricyclics - avoid; concentration increased by fluoxetine and venlafaxine and possibly fluvoxamine; possible increased risk of convulsions with vortioxetine; concentration of tricyclics increased.
Antiepileptics: metabolism increased by carbamazepine, phenobarbital and primidone; lowered seizure threshold; concentration reduced by fosphenytoin and phenytoin.
Antifungals: concentration possibly increased by itraconazole.
Antimalarials: avoid with artemether/lumefantrine and piperaquine with artenimol; possible increased risk of ventricular arrhythmias with mefloquine or quinine - avoid.
Antipsychotics: avoid concomitant use of depot formulations with clozapine (cannot be withdrawn quickly if neutropenia occurs); increased risk of ventricular arrhythmias with sulpiride and droperidol and possibly risperidone - avoid with droperidol; concentration possibly increased by chlorpromazine.
Antivirals: concentration possibly increased with ritonavir; increased risk of ventricular arrhythmias with saquinavir - avoid.
Anxiolytics and hypnotics: increased sedative effects; concentration increased by alprazolam and buspirone.
Atomoxetine: increased risk of ventricular arrhythmias.
Beta-blockers: increased risk of ventricular arrhythmias with sotalol.
Cytotoxics: increased risk of ventricular arrhythmias with bosutinib, ceritinib and vandetanib - avoid with vandetanib; increased risk of ventricular arrhythmias with arsenic trioxide.
Lithium: increased risk of extrapyramidal side effects and possibly neurotoxicity.

Metabolism

Haloperidol is metabolised in the liver and is excreted in the urine and, via the bile in the faeces; there is evidence of enterohepatic recycling. Routes of metabolism of haloperidol include oxidative N-dealkylation, particularly via the cytochrome P450 isoenzymes CYP3A4 and CYP2D6, glucuronidation, and reduction of the ketone group to form an alcohol known as reduced haloperidol. Metabolites are ultimately conjugated with glycine and excreted in the urine. There is debate over the pharmacological activity of the metabolites.

Metabolism

Haloperidol is extensively metabolised in the liver with only about 1% of the administered dose excreted unchanged in urine.
In humans, haloperidol is biotransformed to various metabolites, including p-fluorobenzoylpropionic acid, 4-(4-chlorophenyl)-4-hydroxypiperidine, reduced haloperidol, pyridinium metabolites, and haloperidol glucuronide. In psychiatric patients treated regularly with haloperidol, the concentration of haloperidol glucuronide in plasma is the highest among the metabolites, followed, in rank order, by unchanged haloperidol, reduced haloperidol and reduced haloperidol glucuronide.
The drug is thought to be metabolized primarily by oxidative N-dealkylation of the piperidine nitrogen to form fluorophenylcarbonic acids and piperidine metabolites (which appear to be inactive), and by reduction of the butyrophenone carbonyl to the carbinol, forming hydroxyhaloperidol.
The enzymes involved in the biotransformation of haloperidol include cytochrome P450 (CYP) including CYP3A4 and CYP2D6, carbonyl reductase and uridine di-phosphoglucose glucuronosyltransferase enzymes. The greatest proportion of the intrinsic hepatic clearance of haloperidol is performed by glucuronidation and followed by the reduction of haloperidol to reduced haloperidol and by CYP-mediated oxidation.
In studies of cytochrome-mediated disposition in vitro, CYP3A4 appears to be the major isoform of the enzyme responsible for the metabolism of haloperidol in humans. The intrinsic clearance of the back-oxidation of reduced haloperidol to the parent compound, oxidative N-dealkylation and pyridinium formation are of the same order of magnitude. This suggests that the same enzyme system is responsible for the above three metabolic reactions.
In vivo human studies on haloperidol metabolism have shown that the glucuronidation of haloperidol accounts for 50 to 60% of haloperidol biotransformation and that approximately 23% of the biotransformation was accounted for by the reduction pathway. The remaining 20 to 30% ofthe biotransformation of haloperidol would be via N-dealkylation and pyridinium formation.

Dosage forms

Dosage for haloperidol is as follows:
? Sedation: 2–10 mg i.v. or i.m. (max. 18 mg per 24 h).
? Antiemesis: 1.25 mg i.v. for prevention of postoperative nausea and vomiting (PONV).

References

[1] dr ananya mandal, md .haloperidol pharmacology.