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Haloperidol, marketed under the
Haloperidol is also used on many different kinds of animals. It appears to be particularly successful when given to birds, e.g., a parrot that will otherwise continuously pluck its feathers out.[54]
It is sold under the tradenames Aloperidin, Bioperidolo, Brotopon, Dozic, Duraperidol (Germany), Einalon S, Eukystol, Haldol (common tradename in the US and UK), Halosten, Keselan, Linton, Peluces, Serenace and Sigaperidol.
Haloperidol is the INN, BAN, USAN, AAN approved name.
Haloperidol was approved by the U.S. Food and Drug Administration (FDA) on April 12, 1967; it was later marketed in the U.S. and other countries under the brand name Haldol by McNeil Laboratories.
Haloperidol was discovered by Paul Janssen.[51] It was developed in 1958 at the Belgian company Janssen Pharmaceutica and submitted to the first of clinical trials in Belgium later that year.[52][53]
Haloperidol is heavily protein bound in human plasma, with a free fraction of only 7.5 to 11.6%. It is also extensively metabolized in the liver with only about 1% of the administered dose excreted unchanged in the urine. The greatest proportion of the hepatic clearance is by glucuronidation, followed by reduction and CYP-mediated oxidation, primarily by CYP3A4.[1]
The concentration of haloperidol in brain tissue is about 20-fold higher compared to blood levels. It is slowly eliminated from brain tissue,[49] which may explain the slow disappearance of side effects when the medication is stopped.[49][50]
Plasma levels of four 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.
The bioavailability is 100% in intravenous (IV) injection, and the very rapid onset of action is seen within seconds. The T1/2 is 14.1 to 26.2 hours. The apparent volume of distribution is between 9.5 to 21.7 L/kg.[1] The duration of action is four to six hours. If haloperidol is given as a slow IV infusion, the onset of action is slowed, and the duration of action is prolonged.
The drug is well and rapidly absorbed with a high bioavailability when injected intramuscularly. The Tmax is 20 minutes in healthy individuals and 33.8 minutes in patients with schizophrenia. The mean T1/2 is 20.7 hours.[1] The decanoate injectable formulation is for intramuscular administration only and is not intended to be used intravenously. The plasma concentrations of haloperidol decanoate reach a peak at about six days after the injection, falling thereafter, with an approximate half-life of three weeks.[48]
The bioavailability of oral haloperidol ranges from 60–70%. However, there is a wide variance in reported mean Tmax and T1/2 in different studies, ranging from 1.7 to 6.1 hours and 14.5 to 36.7 hours respectively.[1]
Haloperidol acts on these receptors: (Ki)
Haloperidol is a typical butyrophenone type antipsychotic that exhibits high affinity dopamine D2 receptor antagonism and slow receptor dissociation kinetics.[39] It has effects similar to the phenothiazines.[16] The drug binds preferentially to D2 and Alpha 1 receptors at low dose (ED50 = 0.13 and 0.42 mg/kg, respectively), and 5-HT2 receptors at a higher dose (ED50 = 2.6 mg/kg). Given that antagonism of D2 receptors is more beneficial on the positive symptoms of schizophrenia and 5-HT2 receptors on the negative symptoms, this characteristic underlies haloperidol's greater effect on delusions, hallucinations and other manifestations of psychosis.[40] Haloperidol's negligible affinity for histamine H1 receptors and muscarinic M1 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.
In general, the prognosis of overdose is good, and lasting damage is not known, provided the person has survived the initial phase. An overdose of haloperidol can be fatal.[38]
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. Epinephrine is avoided for treatment of hypotension and shock, because its action might be reversed. In the case of a severe overdose, antidotes such as bromocryptine or ropinirole may be used to treat the extrapyramidal effects caused by haloperidol, acting as dopamine receptor agonists. ECG and vital signs should be monitored especially for QT prolongation and severe arrhythmias should be treated with antiarrhythmic measures.[12]
Symptoms are usually due to side effects. Most often encountered are:
Experimental evidence from animal studies indicates the 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.
Sources for the following lists of adverse effects[30][31][32][33]
Topical formulations of haloperidol should not be used as treatment for nausea because research does not indicate this therapy is more effective than alternatives.[29]
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.[28] The IUPAC name of haloperidol decanoate is 4-(4-chlorophenyl)-1-1[4-(4-fluorophenyl)-4-oxobutyl]-4 piperidinyl decanoate.
Other forms of therapy (psychotherapy, occupational therapy/ergotherapy, or social rehabilitation) should be instituted properly. PET imaging studies have suggested low doses are preferable. Clinical response was associated with at least 65% occupancy of D2 receptors, while greater than 72% was likely to cause hyperprolactinaemia and over 78% associated with extrapyramidal side effects. Doses of haloperidol greater than 5 mg increased the risk of side effects without improving efficacy.[26] Patients responded with doses under even 2 mg in first-episode psychosis.[27] For maintenance treatment of schizophrenia, an international consensus conference recommended a reduction dosage by about 20% every 6 months until a minimal maintenance dose is established.[25]
During long-term treatment of chronic psychiatric disorders, the daily dose should be reduced to the lowest level needed for maintenance of remission. Sometimes, it may be indicated to terminate haloperidol treatment gradually.[24] In addition, during long-term use, routine monitoring including measurement of BMI, blood pressure, fasting blood sugar, and lipids, is recommended due to the risk of side effects.[25]
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, or breastfeeding should be stopped.
Data from animal experiments indicate haloperidol is not teratogenic, but is embryotoxic in high doses. In humans, no controlled studies exist. Reports in pregnant women revealed possible damage to the fetus, although most of the women were exposed to multiple drugs during pregnancy. In addition, reports indicate neonates exposed to antipsychotic drugs are at risk for extrapyramidal and/or withdrawal symptoms following delivery, such as agitation, hypertonia, hypotonia, tremor, somnolence, respiratory distress, and feeding disorder. Following accepted general principles, haloperidol should be given during pregnancy only if the benefit to the mother clearly outweighs the potential fetal risk.[12]
A multiple-year study suggested this drug and other neuroleptic antipsychotic drugs commonly given to Alzheimer's patients with mild behavioural problems often make their condition worse and its withdrawal was even beneficial for some cognitive and functional measures.[23]
Haloperidol was considered indispensable for treating psychiatric emergency situations,[17][18] 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.[19][20][21][22]
Haloperidol is used in the control of the symptoms of:
[10] It is the most commonly used typical antipsychotic.[11] The cost in the United States is around 250 US dollars.[10][9] The yearly cost of the typical dose of haloperidol is about 20 to 800 pounds (30 to 1,250 US dollars) in the United Kingdom.[8].health system, the most important medications needed in a basic WHO Model List of Essential Medicines It is on the [7].meperidine It was made from [6].Paul Janssen Haloperidol was discovered in 1958 by [3].Parkinson's disease It should not be used in people with [5][3] When taken during pregnancy it may result in problems in the infant.[3] it results in an increased risk of death.dementia may occur. In older people with psychosis due to QT-interval prolongation and Neuroleptic malignant syndrome which may be permanent. tardive dyskinesia Haloperidol may result in a movement disorder known as [3]
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