What is the recommended dose of Atarax (hydroxyzine) for a patient with impaired renal function undergoing dialysis?

Hydroxyzine Dosing in Dialysis Patients

For patients on dialysis, hydroxyzine (Atarax) should be administered at a reduced dose of 25-50% of the normal dose, with careful monitoring for side effects. The medication should be given after dialysis sessions to avoid premature removal of the drug.

Pharmacokinetics in Renal Impairment

Hydroxyzine's pharmacokinetics are significantly affected by renal impairment, though the FDA label does not provide specific dosing recommendations for dialysis patients 1. The drug's clearance is altered in patients with decreased renal function, potentially leading to:

• Accumulation of the parent compound
• Extended half-life
• Increased risk of adverse effects
• Higher risk of QT prolongation

Recommended Dosing Algorithm

1. Initial dose: Start at 25-50% of the normal dose (typically 10-25 mg per dose)
2. Timing: Administer after dialysis sessions to prevent drug removal during dialysis 2
3. Frequency: Extend dosing intervals as needed based on clinical response
4. Titration: Increase dose gradually only if needed and if well-tolerated

Monitoring Requirements

When administering hydroxyzine to dialysis patients, closely monitor for:

• CNS depression: Excessive sedation, confusion, drowsiness
• QT prolongation: Particularly important in patients with other risk factors such as electrolyte abnormalities or concomitant use of other QT-prolonging medications 1
• Efficacy: Ensure therapeutic effect is achieved

Special Considerations

Risk Factors Requiring Extra Caution

• Elderly patients: Start at the lowest possible dose due to increased sensitivity to CNS effects 1
• Concomitant medications: Reduce doses of other CNS depressants used with hydroxyzine 1
• Cardiac conditions: Use with extreme caution in patients with:
  • Pre-existing heart disease
  • Electrolyte imbalances (common in dialysis patients)
  • Concomitant use of other QT-prolonging medications

Drug Interactions of Concern in Dialysis

• CNS depressants: Hydroxyzine potentiates effects of narcotics, non-narcotic analgesics, and barbiturates 1
• QT-prolonging medications: Avoid concurrent use with Class 1A or Class III antiarrhythmics, certain antipsychotics, antidepressants, and antibiotics 1

Clinical Pearls

• Hydroxyzine is primarily metabolized by the liver, but its metabolites are excreted renally
• The drug's sedative effects may be more pronounced in dialysis patients
• Patients should be cautioned about driving or operating machinery due to increased risk of drowsiness 1
• Supplemental doses after dialysis are generally not required as hydroxyzine is not significantly removed by dialysis 3

By following these recommendations and closely monitoring patients, hydroxyzine can be used safely in dialysis patients when clinically indicated.