HALOMED INJECTION

Indications

• Schizophrenia
• Acute psychosis
• Acute mania
• Severe agitation
• Tourette syndrome
• Behavioral problems in children

Dosage

Children: Refer to the BNF for Children for appropriate pediatric dosing information based on age and weight.

Adults: Refer to the BNF for specific dosing guidelines based on the condition being treated. Dosing typically begins with low doses, which may be titrated based on clinical response.

Mechanism of action

Haloperidol exerts its effects primarily as a dopamine D2 receptor antagonist in the central nervous system. By blocking these receptors, it reduces dopaminergic neurotransmission, which is believed to be hyperactive in conditions like schizophrenia. This blockade helps alleviate symptoms such as hallucinations, delusions, and agitation.

Pharmacodynamics

Haloperidol's antagonistic activity at D2 receptors leads to decreased dopaminergic activity, contributing to its antipsychotic properties. The drug also exhibits some antagonistic effects at alpha-adrenergic receptors and has minimal activity on serotonin receptors, which may contribute to its profile of side effects and therapeutic effects.

Pharmacokinetics

Haloperidol is well absorbed from the gastrointestinal tract, with peak plasma concentrations occurring within 2 to 6 hours post-ingestion. It is extensively metabolized in the liver, primarily through oxidative pathways involving cytochrome P450 enzymes. The elimination half-life ranges from 12 to 38 hours, allowing for once or twice daily dosing in most cases. The drug is excreted mainly in the urine and feces, with a significant portion as metabolites.

Contra-indications

• Hypersensitivity to haloperidol or any components of the formulation
• Severe central nervous system depression
• Parkinson's disease
• Coma
• Prolonged QT interval or arrhythmias

Adverse effects

• Extrapyramidal symptoms (e.g., tremors, rigidity)
• Sedation or drowsiness
• Weight gain
• Anticholinergic effects (e.g., dry mouth, constipation)
• Neuroleptic Malignant Syndrome (NMS)
• Prolactin elevation leading to galactorrhea or gynecomastia
• Orthostatic hypotension

Interactions

• CNS depressants (e.g., alcohol, benzodiazepines) may enhance sedative effects
• Anticholinergic drugs may increase anticholinergic side effects
• Medications that prolong the QT interval may increase the risk of arrhythmias
• Dopamine agonists may be antagonized

Precautions

• Use with caution in patients with a history of seizures
• Monitor for signs of tardive dyskinesia with long-term use
• Assess cardiovascular status prior to treatment due to potential QT prolongation
• Use cautiously in elderly patients, particularly those with dementia-related psychosis

Pregnancy

Haloperidol should only be used during pregnancy if the potential benefit justifies the potential risk to the fetus. It is classified as Category C.

Breast-feeding

Haloperidol is excreted in breast milk, and nursing mothers should weigh the benefits of treatment against the potential risks to the infant.

Storage

Store at room temperature, away from light and moisture. Keep out of reach of children.

Formulations

• Oral tablets (e.g., 0.5 mg, 1 mg, 5 mg, 10 mg)
• Oral solution
• Intramuscular injection (e.g., 5 mg/mL)
• Depot injection formulations