What are the most common side effects of haloperidol (antipsychotic medication)?

From the Guidelines

Haloperidol commonly causes several significant side effects, with extrapyramidal symptoms (EPS) being the most frequently observed, including acute dystonia, parkinsonism, and akathisia, as well as tardive dyskinesia with long-term use, according to the most recent evidence 1.

Side Effects of Haloperidol

The side effects of haloperidol can be categorized into several groups, including:

• Extrapyramidal symptoms (EPS): These include acute dystonia (muscle spasms, particularly in the neck, tongue, and eyes), parkinsonism (tremor, rigidity, and bradykinesia), and akathisia (inner restlessness and inability to sit still) 1.
• Anticholinergic effects: These include dry mouth, constipation, and urinary retention 1.
• Orthostatic hypotension: This is a drop in blood pressure that occurs when standing up from sitting or lying down, which can lead to dizziness and fainting 1.
• QT interval prolongation: This is a change in the heart's electrical activity that can lead to cardiac arrhythmias, as noted in studies such as 1.
• Neuroleptic malignant syndrome: This is a rare but potentially life-threatening reaction that can occur with the use of haloperidol, characterized by fever, muscle stiffness, and changes in mental status 1.

Management of Side Effects

To manage the side effects of haloperidol, clinicians often prescribe anticholinergic medications like benztropine to manage acute EPS symptoms 1. Additionally, patients starting haloperidol should be monitored closely for these effects, and the dose should be adjusted as needed to minimize the risk of side effects. It is also important to note that the use of haloperidol should be carefully considered in patients with certain medical conditions, such as Parkinson's disease or dementia with Lewy bodies, due to the risk of exacerbating these conditions 1.

From the FDA Drug Label

Tardive Dyskinesia As with all antipsychotic agents, haloperidol has been associated with persistent dyskinesias Tardive dyskinesia, a syndrome consisting of potentially irreversible, involuntary, dyskinetic movements, may appear in some patients on long-term therapy or may occur after drug therapy has been discontinued. Other CNS Effects Insomnia, restlessness, anxiety, euphoria, agitation, drowsiness, depression, lethargy, headache, confusion, vertigo, grand mal seizures, exacerbation of psychotic symptoms including hallucinations and catatonic-like behavioral states which may be responsive to drug withdrawal and/or treatment with anticholinergic drugs Body as a Whole:Neuroleptic malignant syndrome (NMS), hyperpyrexia and heat stroke have been reported with haloperidol. Hematologic Effects:Reports have appeared citing the occurrence of mild and usually transient leukopenia and leukocytosis, minimal decreases in red blood cell counts, anemia, or a tendency toward lymphomonocytosis. Gastrointestinal Effects:Anorexia, constipation, diarrhea, hypersalivation, dyspepsia, nausea and vomiting.

The most common side effects of haloperidol are:

• CNS effects:
  • Insomnia
  • Restlessness
  • Anxiety
  • Euphoria
  • Agitation
  • Drowsiness
  • Depression
  • Lethargy
  • Headache
  • Confusion
  • Vertigo
• Gastrointestinal effects:
  • Anorexia
  • Constipation
  • Diarrhea
  • Hypersalivation
  • Dyspepsia
  • Nausea
  • Vomiting
• Hematologic effects:
  • Leukopenia
  • Leukocytosis
  • Anemia
• Body as a whole:
  • Neuroleptic malignant syndrome (NMS)
  • Hyperpyrexia
  • Heat stroke 2

From the Research

Common Side Effects of Haloperidol

The most common side effects seen with haloperidol are related to extrapyramidal symptoms (EPS), which include:

• Parkinsonism
• Akathisia
• Dystonia
• Dyskinesia
• Tardive dyskinesia [ 3, 4, 5, 6, 7 ]

Factors Influencing Side Effects

The incidence of EPS with haloperidol can be influenced by factors such as:

• Dose: Higher doses of haloperidol are associated with a higher incidence of parkinsonism [ 5 ]
• Age: Younger patients are more likely to experience parkinsonism [ 5 ]
• Method of administration: Smoking haloperidol can lead to acute dystonia [ 6 ]

Comparison with Other Antipsychotics

Haloperidol has been compared to other antipsychotics, such as olanzapine, in terms of EPS:

• Olanzapine has been shown to have a lower incidence of EPS compared to haloperidol [ 3 ]
• Risperidone has been shown to have a similar incidence of EPS compared to haloperidol at comparable D2 receptor occupancy levels [ 7 ]