What should be done if a patient experiences hallucinations while taking hydroxyzine (an antihistamine)?

Management of Hydroxyzine-Induced Hallucinations

If a patient experiences hallucinations while taking hydroxyzine, the medication should be immediately discontinued and replaced with an alternative non-sedating antihistamine if antihistamine therapy is still required.

Understanding Hydroxyzine and Hallucinations

Hydroxyzine is a first-generation antihistamine with sedating properties that is commonly used for:

• Treatment of anxiety
• Management of pruritus (itching)
• Sedation
• Treatment of urticaria

While hallucinations are not commonly listed among the typical side effects of hydroxyzine in most guidelines, case reports indicate that hydroxyzine can cause neuropsychiatric effects including hallucinations 1. The FDA label for hydroxyzine specifically warns about its CNS depressant effects and potential for causing confusion, particularly in elderly patients 2.

Assessment and Management Algorithm

1. Immediate Actions

• Discontinue hydroxyzine immediately
• Assess vital signs and neurological status
• Determine if the patient has any risk factors:
  • Elderly patients (more susceptible to CNS effects) 2
  • Hepatic impairment (hydroxyzine should be avoided in severe liver disease) 3
  • Renal impairment (dose should be halved in moderate renal impairment) 3
  • Concomitant use of other CNS depressants 2

2. Supportive Care

• Provide reassurance to the patient
• Maintain a calm environment with decreased sensory stimulation 3
• Monitor for other neuropsychiatric symptoms
• If hallucinations are severe or causing distress:
  • Consider short-term use of benzodiazepines for acute management 3
  • In extreme cases with persistent hallucinations, antipsychotic drugs may be required 3

3. Alternative Treatment Options

• If antihistamine therapy is still required, switch to a non-sedating second-generation antihistamine:

  • Cetirizine (though it may be somewhat sedating at higher doses) 3
  • Loratadine
  • Desloratadine
  • Fexofenadine

• Second-generation antihistamines are generally preferred over first-generation antihistamines like hydroxyzine due to:

  • Lower risk of sedation and cognitive impairment 3
  • Reduced anticholinergic effects 3
  • Lower risk of performance impairment 3

Important Considerations and Pitfalls

Risk Factors for Adverse CNS Effects

• Elderly patients are at higher risk for confusion, over-sedation, and falls with hydroxyzine 2
• Concomitant use of CNS depressants (narcotics, barbiturates, benzodiazepines, alcohol) potentiates hydroxyzine's effects 2
• QT prolongation risk - hydroxyzine can prolong QT interval, especially when combined with other QT-prolonging medications 2, 4
• Renal or hepatic impairment can increase risk of adverse effects 3

Documentation and Reporting

• Document the adverse reaction in the patient's medical record
• Consider reporting the adverse event to appropriate pharmacovigilance systems
• Ensure the patient understands the need to avoid hydroxyzine in the future

Follow-up

• Evaluate the patient within 1-2 weeks to ensure resolution of symptoms
• Assess effectiveness of alternative medication if prescribed
• Reinforce education about avoiding hydroxyzine and similar first-generation antihistamines

Remember that hallucinations with hydroxyzine may be part of a spectrum of CNS effects that can range from mild sedation to more severe manifestations including confusion, delirium, and in rare cases, catatonia 5. The primary intervention is medication discontinuation, which typically leads to resolution of symptoms.