haloperidol
Apo-Haloperidol ◆, Haldol, Novo-Peridol ◆, Peridol ◆

haloperidol decanoate
Haldol Decanoate 50, Haldol Decanoate 100, Haldol LA ◆

haloperidol lactate
Haldol, Haldol Concentrate, Haloperidol Intensol

Pharmacologic classification: butyrophenone
Therapeutic classification: antipsychotic
Pregnancy risk category C


Available forms
Available by prescription only
haloperidol
Tablets: 0.5 mg, 1 mg, 2 mg, 5 mg, 10 mg, 20 mg
haloperidol decanoate
Injection: 50 mg/ml, 100 mg/ml
haloperidol lactate
Injection: 5 mg/ml
Oral concentrate: 2 mg/ml

Indications and dosages
 Psychotic disorders; alcohol dependence (adults only). Adults: Dosage varies for each patient and for different symptoms. Initial dosage range is 0.5 to 5 mg P.O. b.i.d. or t.i.d.; or, 2 to 5 mg I.M. q 4 to 8 hours, increased rapidly if needed for prompt control. Maximum dose is 100 mg P.O. daily. Doses of more than 100 mg have been used to treat patients who have severely resistant conditions.
Children ages 3 to 12: Usual initial dose is 0.5 mg P.O. daily given in two or three divided doses. Subsequent dosing may be increased by 0.5 mg daily at 5- to 7-day intervals. Usual maintenance dosage range is 0.05 to 0.15 mg/kg daily divided in two or three doses.
 Psychotic patients who require prolonged therapy. Adults: 100 mg I.M. of haloperidol decanoate q 4 weeks. Experience with doses of more than 450 mg monthly is limited.
 Control of tics, vocal utterances in Tourette syndrome. Adults: 0.5 to 2 mg P.O. b.i.d. or t.i.d., increased, p.r.n.
Children ages 3 to 12: 0.05 to 0.075 mg/kg daily given b.i.d. or t.i.d.
 Delirium. Adults: 1 to 2 mg I.V. every 2 to 4 hours.

Pharmacodynamics
Antipsychotic action: Haloperidol is thought to exert antipsychotic effects by strong postsynaptic blockade of CNS dopamine receptors, thereby inhibiting dopamine-mediated effects; its pharmacologic effects are most similar to those of piperazine antipsychotics. Its mechanism of action in Tourette syndrome is unknown.
Haloperidol has many other central and peripheral effects; it has weak peripheral anticholinergic effects and antiemetic effects, produces both alpha and ganglionic blockade, and counteracts histamine- and serotonin-mediated activity. Its most prominent adverse reactions are extrapyramidal.

Pharmacokinetics
Absorption: Rate and extent of absorption vary with route of administration. Oral administration yields 60% bioavailability.
Distribution: Distributed widely into body, with high levels in adipose tissue. Drug is 90% to 92% protein-bound.
Metabolism: Metabolized extensively by the liver; there may be only one active metabolite that’s less active than parent drug.
Excretion: About 40% of a given dose is excreted in urine within 5 days; about 15% is excreted in feces via the biliary tract.

Route Onset Peak Duration
P.O. Unknown 3-6 hr Unknown
I.M.
 decanoate Unknown 3-9 days Unknown
 lactate Unknown 10-20 min Unknown


Contraindications and precautions
Contraindicated in patients hypersensitive to drug and in those experiencing parkinsonism, coma, or CNS depression.
  Use haloperidol cautiously in elderly or debilitated patients; in patients with history of seizures, EEG abnormalities, CV disorders, allergies, angle-closure glaucoma, or urine retention; and in those receiving anticoagulants, anticonvulsants, antiparkinsonians, or lithium.

Interactions
Drug-drug. Aluminum- and magnesium-containing antacids and antidiarrheals: Decreases drug absorption. Separate administration times by 2 hours.
Antiarrhythmics, disopyramide, procainamide, quinidine: Increases risk of arrhythmias and conduction defects. Avoid use together.
Anticholinergics, including antidepressants, antihistamines, antiparkinsonians, atropine, MAO inhibitors, meperidine, phenothiazines: Causes oversedation, paralytic ileus, visual changes, and severe constipation. Use cautiously.
Beta blockers: May inhibit haloperidol metabolism, increasing plasma levels and toxicity. Use cautiously.
Bromocriptine: Antagonizes therapeutic effect of bromocriptine on prolactin secretion. Avoid use together.
Centrally acting antihypertensives (such as clonidine, guanabenz, guanadrel, guanethidine, methyldopa, reserpine): Inhibits blood pressure response. Monitor blood pressure carefully.
CNS depressants, including analgesics, barbiturates, narcotics, tranquilizers, and general, spinal, or epidural anesthetics; parenteral magnesium sulfate: Increases CNS depression. Avoid use together.
Dopamine: Decreases vasoconstricting effects. Monitor patient for lack of therapeutic effect.
Levodopa: Decreases effectiveness and increases toxicity of levodopa. Avoid use together.
Lithium: May result in severe neurologic toxicity with an encephalitis-like syndrome and a decreased therapeutic response to haloperidol. Use cautiously; monitor patient.
Metrizamide: Increases risk of seizures. Avoid use together.
Nitrates: Causes hypotension. Monitor blood pressure frequently.
Phenobarbital: Enhances renal excretion. Monitor patient closely.
Phenytoin: Inhibits metabolism and increases toxicity of phenytoin. Avoid use together.
Propylthiouracil: Increases risk of agranulocytosis. Avoid use together.
Rifampin: Decreases haloperidol levels and efficacy. Monitor patient carefully.
Sympathomimetics, including ephedrine, epinephrine, and phenylephrine (often found in nasal sprays): May decrease stimulatory and pressor effects of these drugs. Monitor patient carefully.
Drug-herb. Nutmeg: Causes loss of symptom control; interferes with psychiatric drug therapy. Discourage use together.
Drug-lifestyle. Heavy smoking: Increases haloperidol metabolism. Discourage smoking.

Adverse reactions
CNS: severe extrapyramidal reactions, tardive dyskinesia, sedation, drowsiness, lethargy, headache, insomnia, confusion, vertigo, seizures, neuroleptic malignant syndrome.
CV: tachycardia, hypotension, hypertension, ECG changes.
EENT: blurred vision.
GI: dry mouth, anorexia, constipation, diarrhea, nausea, vomiting, dyspepsia.
GU: urine retention, menstrual irregularities, priapism.
Hematologic: leukopenia, leukocytosis.
Hepatic: jaundice.
Skin: rash, other skin reactions, diaphoresis.
Other: gynecomastia.

Effects on lab test results
• May increase liver function test values. May increase or decrease WBC count.

Overdose and treatment
Overdose increases the severity of adverse reactions and can include deep or unarousable sleep, coma, hypotension, hypertension, extrapyramidal symptoms, dystonia, abnormal involuntary muscle movements, agitation, seizures, arrhythmias, ECG changes (may show QT interval prolongation and torsades de pointes), hypothermia, hyperthermia, and autonomic nervous system dysfunction. Overdose with long-acting decanoate requires prolonged recovery time.
 Treatment is symptomatic and supportive, including maintaining vital signs, airway, stable body temperature, and fluid and electrolyte balance. Ipecac may be used to induce vomiting, with due regard for antiemetic properties of haloperidol and hazard of aspiration. Gastric lavage also may be used, followed by activated charcoal and saline cathartics; dialysis doesn’t help.
 Regulate body temperature as needed. Treat hypotension with I.V. fluids; don’t give epinephrine. Treat seizures with parenteral diazepam or barbiturates. Treat arrhythmias with appropriate antiarrhythmics in addition to ECG monitoring. May repeat every 5 minutes up to 10 mg/kg. Treat extrapyramidal reactions with benztropine at 1 to 2 mg or parenteral diphenhydramine at 10 to 50 mg.

Special considerations
• Drug has few CV adverse effects and may be preferred in patients with cardiac disease.
• Dose of 2 mg is therapeutic equivalent of 100 mg chlorpromazine.
• When changing from tablets to decanoate injection, patient should initially receive 10 to 20 times the oral dose once monthly (not more than 100 mg).
• Assess patient periodically for extrapyramidal reactions and tardive dyskinesia.
• Don’t withdraw drug abruptly except when required, because abrupt withdrawal may cause severe adverse reaction. Taper dosage over several weeks.
Pediatric patients
• Safety and efficacy of drug injection in children haven’t been established, and oral drug isn’t recommended for children younger than age 3.
Geriatric patients
• Drug is especially useful for agitation related to senile dementia. Tardive dyskinesia may occur more often, especially in elderly women.
• Elderly patients usually need lower initial doses and a more gradual dosage adjustment.

Patient education
• Warn patient against activities that require alertness and good psychomotor coordination until CNS response to drug is determined. Tell him that drowsiness and dizziness usually subside after a few weeks.
• Tell patient to report adverse effects.
• Instruct patient to avoid alcohol or other depressants.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use