What happens if a patient overdoses on haloperidol (antipsychotic medication)?

From the Guidelines

Haloperidol overdose is a medical emergency that requires immediate attention, as it can cause severe and potentially life-threatening symptoms, including QT prolongation, torsades de pointes, and neuroleptic malignant syndrome, as highlighted in the 2013 clinical practice guidelines for the management of pain, agitation, and delirium in adult patients in the intensive care unit 1.

Symptoms of Haloperidol Overdose

Patients who overdose on haloperidol may experience:

• Severe central nervous system depression
• Extreme drowsiness
• Confusion
• Coma
• Cardiovascular effects, including hypotension and tachycardia
• Potentially dangerous heart rhythm abnormalities, such as QT prolongation, which can lead to torsades de pointes, a potentially fatal arrhythmia, as warned by the 2013 guidelines 1
• Extrapyramidal symptoms, including muscle rigidity, tremors, and dystonic reactions
• Neuroleptic malignant syndrome, characterized by high fever, muscle rigidity, altered mental status, and autonomic instability
• Anticholinergic effects, such as dry mouth, blurred vision, urinary retention, and hyperthermia

Treatment for Haloperidol Overdose

Treatment for haloperidol overdose is primarily supportive, focusing on:

• Maintaining vital functions
• Cardiac monitoring
• Managing specific symptoms
• Administering activated charcoal if the overdose was recent
• Using benzodiazepines to manage agitation or seizures
• Using anticholinergic medications, such as benztropine, to help with extrapyramidal symptoms, as suggested by the 2018 clinical practice guidelines for the prevention and management of pain, agitation/sedation, delirium, immobility, and sleep disruption in adult patients in the ICU 1 It is essential to seek medical attention immediately for any suspected haloperidol overdose, as the consequences of delayed treatment can be severe and potentially fatal, emphasizing the need for cautious use of haloperidol, especially in patients at high risk for torsades de pointes, as recommended by the 2013 guidelines 1.

From the FDA Drug Label

Manifestations In general, the symptoms of overdosage would be an exaggeration of known pharmacologic effects and adverse reactions, the most prominent of which would be: 1) severe extrapyramidal reactions, 2) hypotension, or 3) sedation. The patient would appear comatose with respiratory depression and hypotension which could be severe enough to produce a shock-like state The extrapyramidal reaction would be manifest by muscular weakness or rigidity and a generalized or localized tremor as demonstrated by the akinetic or agitans types respectively. The risk of ECG changes associated with Torsades de pointes should be considered.

If a patient overdoses on haloperidol, they may experience:

• Severe extrapyramidal reactions
• Hypotension
• Sedation
• Respiratory depression
• Coma
• Shock-like state
• ECG changes associated with Torsades de pointes Treatment is primarily supportive and may include:
• Gastric lavage or induction of emesis
• Administration of activated charcoal
• Establishment of a patent airway
• Artificial respiration and mechanical respirators
• Intravenous fluids, plasma, or concentrated albumin, and vasopressor agents
• Antiparkinson medication for severe extrapyramidal reactions
• Monitoring of ECG and vital signs 2

From the Research

Effects of Haloperidol Overdose

• Overdose of haloperidol can cause serious cardiovascular side effects, including hypotension, cardiac arrhythmias, and prolongation of the corrected QT (QTc) interval 3.
• Torsade de pointes, a polymorphic ventricular tachyarrhythmia, has been associated with both intravenous and oral haloperidol administration 3, 4.
• In cases of oral haloperidol decanoate intoxication, treatment with oral activated charcoal and laxative may be sufficient to prevent serious events 5.
• Haloperidol-induced sudden cardiac arrest is a rare but potentially fatal complication of haloperidol overdose 6.
• Postmortem toxicological analysis has identified haloperidol in cases of suicidal overdose, with blood concentrations ranging from 0.6 to 1.9 mg/L 7.

Management of Haloperidol Overdose

• Discontinuation of the possible offending agent(s) is crucial in managing torsade de pointes associated with haloperidol overdose 3.
• Correction of electrolyte abnormalities and administration of magnesium sulfate may also be necessary 3.
• Overdrive pacing may be required in severe cases of torsade de pointes 3.
• QTc interval determination is preferable to QT interval dispersion as a means of assessing the risk of haloperidol-induced torsades de pointes 4.

Risk Factors for Haloperidol-Induced Torsades de Pointes

• Prolongation of the QTc interval is a significant risk factor for haloperidol-induced torsades de pointes, with odds increasing in patients with QTc interval > 521 ms during haloperidol therapy 4.
• Increased QT interval dispersion may also be a risk factor, although its significance is dependent on the method of measurement 4.