How should hydroxyzine be dosed for adults and children for itching, anxiety, and sleep, including dose adjustments for the elderly and patients with hepatic impairment?

Hydroxyzine Dosing Guidelines

For adults, hydroxyzine is dosed at 10-50 mg at bedtime for pruritus and urticaria, with dose reductions required in elderly patients and those with moderate renal impairment (halve the dose), and should be avoided entirely in severe hepatic disease. 1, 2

Standard Adult Dosing by Indication

Pruritus and Urticaria

• Primary regimen: 10-50 mg at bedtime as adjunctive therapy to non-sedating antihistamines during the day 1, 2
• Most commonly used dose: 50 mg at bedtime, which provides sustained effects into the next day due to hydroxyzine's long half-life 2
• Hydroxyzine is not recommended as first-line monotherapy due to sedating properties and performance impairment 1, 3
• The bedtime dosing strategy minimizes daytime sedation while maintaining H1-receptor blockade the following morning 4

Anxiety

• Fixed dose: 50 mg daily (typically given as a single dose or divided) 5, 6
• Anxiolytic effects begin within the first week and are maintained throughout 4 weeks of treatment 5, 6
• Not considered first-line due to limited high-quality evidence compared to other anxiolytics 3

Steroid-Refractory Pruritus (Immune Checkpoint Inhibitor Toxicity)

• Dose: 10-25 mg four times daily or at bedtime, combined with topical corticosteroids 2

Pediatric Dosing

• Standard dose: 0.7 mg/kg three times daily for atopic dermatitis and pruritus 7
• This dose provides >85% pruritus suppression from 2-12 hours post-administration 7
• Higher doses (1.4 mg/kg three times daily) offer no additional efficacy but cause significantly more sedation 7
• Elimination half-life is shorter in children (mean 7.1 hours) and increases with age 7, 8

Critical Dose Adjustments

Renal Impairment

• Moderate renal impairment (creatinine clearance 10-20 mL/min): Reduce dose by half 1, 2
• Severe renal impairment (creatinine clearance <10 mL/min): Avoid hydroxyzine entirely 1

Hepatic Impairment

• Severe liver disease: Avoid hydroxyzine completely due to inappropriate sedating effects and risk of precipitating hepatic coma 1, 2

Elderly Patients

• Start at the low end of the dosing range (10 mg) due to decreased hepatic, renal, and cardiac function 2, 3
• Elderly adults are at significantly higher risk for sedative effects, falls, fractures, anticholinergic effects, and cognitive impairment 2, 3
• Hydroxyzine is specifically listed as a medication to deprescribe in older adults due to fall risk 2

Contraindications and High-Risk Situations

Absolute Contraindications

• Early pregnancy: Hydroxyzine is the only antihistamine specifically contraindicated during early stages of pregnancy 1, 3
• Severe hepatic disease 1, 2
• Severe renal impairment 1

Relative Contraindications and Cautions

• Avoid in patients requiring optimal cognitive function (students, workers, drivers) due to persistent performance impairment 2
• Avoid concomitant use with other CNS depressants (dramatically enhances performance impairment and sedation) 2
• Use extreme caution in elderly patients with:
  • Prostatic hypertrophy 2
  • Elevated intraocular pressure 2
  • Pre-existing cognitive impairment 2

Critical Safety Warnings

Performance Impairment

• Drivers taking hydroxyzine are 1.5 times more likely to be responsible for fatal automobile accidents 2, 3
• Performance impairment occurs even without subjective awareness of drowsiness 2
• Impairment persists with bedtime-only dosing due to hydroxyzine's long half-life (approximately 20 hours in adults) 2, 8
• Hydroxyzine causes 80% sedation rates compared to 50% with diphenhydramine 2

Common Pitfalls to Avoid

• Do not use AM/PM split dosing (e.g., non-sedating antihistamine in morning, hydroxyzine at night split into two doses) as hydroxyzine's long half-life causes significant daytime impairment 2
• Do not assume tolerance will develop to performance impairment—it may not 2
• Do not use for delirium management due to sedating and anticholinergic properties 2
• Avoid multiple daily dosing as it significantly increases risk of daytime drowsiness, performance impairment, and cognitive effects 2

Practical Dosing Algorithm

For urticaria/pruritus with sleep disturbance:

1. Start non-sedating antihistamine (e.g., loratadine 10 mg) in the morning 3, 9
2. Add hydroxyzine 10-50 mg at bedtime if sleep disturbance persists 1, 2, 3
3. Adjust hydroxyzine dose based on tolerability and renal function 3
4. Reduce dose by half in moderate renal impairment 1, 2
5. Start at 10 mg in elderly patients 2, 3

For anxiety:

• Use 50 mg daily as a single dose or divided 5, 6
• Expect onset of anxiolytic effects within first week 5, 6

For pediatric atopic dermatitis:

• Use 0.7 mg/kg three times daily 7
• Do not exceed this dose as higher doses provide no additional benefit 7