Other Names/Brands

Haldol, Haldol Decanoate, Dores, Govotil, Lodomer, Seradol, Upsikis, and Serenace

Mechanism of Action

The primary mechanism of action of haloperidol is closely related to its antagonism of dopamine receptors, specifically the D2 receptor. It binds to the D2 receptor without activating it, thereby inhibiting the action of dopamine, a neurotransmitter that plays a key role in regulating emotions, perception, and cognitive function.

This mechanism is most prominent in the mesolimbic dopaminergic pathway, which is believed to be central to the development of psychotic symptoms such as hallucinations and delusions. By inhibiting dopamine stimulation in this pathway, haloperidol can alleviate positive symptoms in schizophrenia and other psychotic disorders.

Indications

Haloperidol is indicated for the treatment of various psychiatric and neurological disorders associated with dopaminergic hyperactivity in the brain. This medication is primarily used in the treatment of schizophrenia, particularly to control positive symptoms such as hallucinations, delusions, and aggressive behavior.

In addition, haloperidol is also effective in treating acute agitation, mania in bipolar disorder, and psychosis due to drug or alcohol intoxication. In psychiatric emergency settings, haloperidol is often used to calm patients experiencing severe behavioral disturbances or severe agitation. This medication is also used to treat Tourette's syndrome, particularly in reducing the frequency and intensity of motor and vocal tics.

In neurology, haloperidol is sometimes prescribed to control severe nausea and vomiting that does not respond to standard therapy and is used as an adjunct to acute delirium. Although effective, the use of haloperidol should be considered carefully due to the potential for side effects, particularly extrapyramidal symptoms and heart rhythm disturbances.

Contraindications

Haloperidol has several important contraindications that must be considered because its use can pose serious risks in certain conditions. The main contraindication for haloperidol is in individuals who have a hypersensitivity or allergy to haloperidol or any component of the drug's formulation. This drug should also not be given to patients with Parkinson's disease, as haloperidol works by blocking dopamine, which is already very low in Parkinson's patients, thus worsening motor symptoms.

Furthermore, haloperidol is contraindicated in patients with severe central nervous system disorders, such as coma or severe central nervous system depression, as it may worsen the loss of consciousness. Haloperidol is also contraindicated in patients with a history of cardiac arrhythmias, as it can prolong the QT interval on an ECG and increase the risk of torsades de pointes (a life-threatening arrhythmia). Patients with a history of severe cardiac disorders, hypokalemia, or hypomagnesemia should also not use haloperidol without close monitoring.

Additional contraindications include concomitant use of other medications that can prolong the QT interval or adversely affect the heart. Therefore, before administering haloperidol, it is important to thoroughly assess the patient's health. These tests typically include an ECG (electrocardiogram) and blood electrolyte levels to ensure that haloperidol use is safe and does not pose serious risks to the heart.

Side Effects

Haloperidol can cause a variety of side effects, ranging from mild to serious. The most common side effects are movement disorders, also known as extrapyramidal symptoms, such as tremors, muscle stiffness, slowed movement, sudden muscle spasms, or restlessness that makes it difficult for the patient to remain still. Long-term use can also cause tardive dyskinesia, which is uncontrolled movements of the face, tongue, or limbs, which can persist even after the drug is discontinued.

Furthermore, haloperidol can increase prolactin levels in the body, which can cause menstrual irregularities, breast milk production without breastfeeding, breast enlargement in men, and sexual dysfunction. Other side effects include drowsiness, dizziness, dry mouth, constipation, and sometimes a drop in blood pressure upon standing.

In more severe cases, haloperidol can affect heart rhythm and cause a life-threatening condition called torsades de pointes. One of the most serious, but rare, side effects is neuroleptic malignant syndrome, characterized by high fever, severe muscle stiffness, changes in blood pressure, and decreased consciousness.

Preparations

Haloperidol is available in various dosage forms to suit the patient's condition and needs. The choice of dosage form depends on the patient's condition, symptom severity, and treatment goals. This medication is very useful for improving patient compliance with long-term therapy. The following are commonly used dosage forms of haloperidol:

• Oral tablets

Preparations: 0.5 mg, 1 mg, 2 mg, 5 mg, and 10 mg

Used for long-term treatment or outpatient care of patients with psychotic disorders

• Intramuscular injection

Preparation: 5 mg/mL

Used in psychiatric emergencies such as acute agitation or severe psychosis, especially if the patient is uncooperative or unable to take medication.

• Long-acting/depot injection (haloperidol decanoate)

Preparations: 50 mg/mL or 100 mg/mL

Administered intramuscularly every 4 weeks, it is used for patients with chronic schizophrenia or those who have difficulty adhering to daily medication.

• Oral drops (haloperidol drops)

Preparation: 2 mg/mL

Used for patients who have difficulty swallowing tablets, such as the elderly or patients with neurological disorders.

Dosage

The dose of haloperidol varies depending on the condition being treated, the patient's age, response to treatment, and the dosage form used. Dose adjustments are necessary for elderly patients, those with liver problems, or those taking other medications. The dose should be determined and monitored by a healthcare professional, as the risk of side effects such as extrapyramidal symptoms and heart rhythm disturbances increases with dose increases.

Oral dosage (tablets or drops)

• Adults—schizophrenia or acute psychosis

Initial dose: 0.5 mg to 5 mg, 2–3 times daily

Maintenance dose: 5–15 mg per day (adjustable)

Maximum dose: Up to 30–40 mg/day in severe cases, but should be under close supervision

• Elderly: Initial dose is lower, usually 0.5–2 mg/day, divided into 1–2 doses

The dose is increased slowly as the patient tolerates it

Intramuscular injection dosage

Used in emergencies such as severe agitation or acute psychosis

Adults: 2.5–10 mg per injection, may be repeated every 4–8 hours if necessary

Maximum daily dose: 20–30 mg (depending on the patient's condition)

Depot injection (haloperidol decanoate)

Used for long-term maintenance, given every 4 weeks

Initial dose: 25–100 mg, may be adjusted based on response

Maintenance dose: 50–300 mg every 4 weeks

Safety of Drugs

Haloperidol is classified as a pregnancy category C by the FDA, meaning animal studies have shown a risk to the fetus, but there are no controlled studies in humans. This drug may still be used in pregnant women if the benefits are considered to outweigh the risks, such as in cases of severe psychotic disorders.

Haloperidol is described as having potential risks in pregnancy, but its use is permitted under close medical supervision. Furthermore, haloperidol can pass into breast milk, so if used while breastfeeding, the infant should be monitored for possible side effects such as sedation or movement disorders.

Drug Interactions

Haloperidol can interact with various other medications, which may increase the risk of side effects or reduce its effectiveness. One important interaction is with medications that can prolong the QT interval in the heart, such as some antibiotics (e.g., erythromycin), antidepressants, antifungals, and antiarrhythmics, as this combination may increase the risk of serious heart rhythm disturbances.

Haloperidol may also interact with central nervous system depressants such as benzodiazepines, antihistamines, or alcohol, which can cause excessive sedation or respiratory distress.

Concomitant use of antiparkinsonism medications, such as levodopa, can counteract each other's effects, as haloperidol inhibits dopamine while levodopa increases it. Interactions may also occur with medications that affect liver enzymes (CYP3A4 and CYP2D6), such as rifampin or fluoxetine, which can alter haloperidol blood levels.

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