Haloperidol Mercury Pharmaceuticals (Ireland) (Haloperidol)

Haloperidol intramuscular injection is indicated for the short‑term management of several psychiatric conditions where rapid control of symptoms is required.

• Schizophrenia, particularly during acute exacerbations or when oral therapy is not feasible.
• Acute psychotic episodes associated with mood disorders or substance‑induced states.
• Severe agitation or aggression that requires prompt calming in emergency or inpatient settings.
• Management of tics, including those related to Tourette syndrome, when other treatments are insufficient.
• Pre‑operative sedation in patients with known psychotic disorders.

Side effects of haloperidol injection vary in frequency and severity; they reflect its dopamine antagonism and can affect multiple organ systems.

Common

• Drowsiness, fatigue, or sedation.
• Extrapyramidal symptoms such as tremor, rigidity, or akathisia.
• Dry mouth, constipation, or blurred vision.
• Orthostatic hypotension leading to dizziness on standing.

Serious

• Neuroleptic malignant syndrome, characterized by fever, muscle rigidity, and autonomic instability.
• Torsades de pointes or other significant cardiac arrhythmias.
• Severe depression or suicidal thoughts, especially during early treatment.

When prescribing haloperidol injection, clinicians should evaluate patient history and monitor for conditions that may increase risk of adverse outcomes.

• History of cardiovascular disease, prolonged QT interval, or electrolyte disturbances.
• Current or past diagnosis of Parkinson’s disease or other movement disorders.
• Pregnancy (Category C) and breastfeeding; benefits must outweigh potential fetal risks.
• Elderly patients, especially those with dementia‑related psychosis, due to higher sensitivity to sedation and falls.
• Severe hepatic or renal impairment that may alter drug clearance.
• Concomitant use of other dopamine‑blocking agents, which can amplify extrapyramidal effects.
• Known hypersensitivity to haloperidol or any component of the formulation.

Haloperidol can interact with several medications, affecting its plasma concentration or enhancing adverse effects; awareness of these interactions supports safe use.

Avoid

• Other antipsychotics or dopamine antagonists that increase risk of extrapyramidal symptoms.
• Medications that prolong the QT interval, such as certain antiarrhythmics, macrolide antibiotics, or fluoroquinolones.
• Strong CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin) that may raise haloperidol levels.

Use with caution

• CYP3A4 inducers like carbamazepine or rifampin, which can reduce therapeutic effect.
• CNS depressants, including benzodiazepines or opioids, that may enhance sedation and respiratory depression.
• Anticholinergic agents, which can mask early signs of extrapyramidal side effects.