What is the maximum recommended dose of hydroxyzine (antihistamine) per day?

Maximum Recommended Dose of Hydroxyzine

The maximum recommended daily dose of hydroxyzine is 400 mg per day for adults, administered in divided doses. 1

Dosage Guidelines

Hydroxyzine dosing varies based on indication and patient factors:

• For anxiety and tension relief:

  • Adults: 50-100 mg four times daily (maximum 400 mg/day) 1
  • Children over 6 years: 50-100 mg daily in divided doses
  • Children under 6 years: 50 mg daily in divided doses

• For pruritus management:

  • Adults: 25 mg three to four times daily (maximum 100 mg/day) 1
  • Children over 6 years: 50-100 mg daily in divided doses
  • Children under 6 years: 50 mg daily in divided doses

• As a pre-procedural sedative:

  • Adults: 50-100 mg as a single dose 1
  • Children: 0.6 mg/kg body weight

Special Patient Populations

Elderly Patients

• Reduced dosing is recommended due to increased risk of cognitive decline, falls, and anticholinergic effects 2
• Start with lower doses and titrate cautiously

Hepatic Impairment

• Patients with liver disease require dose adjustments
• Recommended starting dose: half the standard dose with careful monitoring for side effects 2
• Hydroxyzine undergoes extensive hepatic metabolism 3

Renal Impairment

• Dose reduction required
• The elimination half-life of antihistamines can be greatly prolonged in chronic renal disease 3

Administration Considerations

• Timing: Evening dosing may help mitigate daytime sedation and psychomotor impairment 4

  • When administered as a single bedtime dose (50 mg), hydroxyzine maintains H1-receptor antagonism the following morning while minimizing daytime reaction time impairment 4

• Duration: Despite its relatively long half-life (approximately 20 hours), hydroxyzine is typically administered in divided doses throughout the day for most indications 3

Side Effects and Monitoring

• Common side effects:

  • Sedation (most common, reported in 28% vs 14% with placebo) 5
  • Dry mouth (14% vs 5% with placebo) 5
  • Weight gain (12% vs 10% with placebo) 5
  • Impaired concentration (9% vs 8% with placebo) 5

• Psychomotor impairment:

  • Hydroxyzine significantly prolongs both simple and choice reaction times 6
  • This effect does not demonstrate tolerance development during 5 days of administration 6
  • Subjective symptoms are unreliable predictors of objective performance impairment 6

Clinical Pearls

• Hydroxyzine's sedative effects often appear during the first week of treatment and progressively diminish with continued use 5
• After 3 weeks of daily hydroxyzine use, partial tolerance to its antihistamine effects may develop 7
• When used for anxiety, hydroxyzine (50 mg/day) produces significant anxiolytic effects starting in the first week and maintained throughout treatment 5
• Abrupt discontinuation does not appear to cause rebound anxiety or withdrawal symptoms 5

Important Cautions

• Avoid use during early pregnancy 2
• Monitor for anticholinergic effects, especially in elderly patients 2
• Consider alternative treatments for patients who need to perform critical tasks due to hydroxyzine's significant impact on reaction times 6