What is the appropriate dose of hydroxyzine (antihistamine) for an adult patient with anxiety or itching?

Hydroxyzine Dosing for Adults

For pruritus (itching), use hydroxyzine 10-25 mg four times daily or at bedtime; for anxiety, use 50-100 mg four times daily. 1

Pruritus/Itching Management

The optimal dosing strategy for itching is hydroxyzine 10-50 mg at bedtime as an adjunct to non-sedating antihistamines during the day. 2, 3

• For mild to moderate pruritus, the FDA-approved dose is 25 mg three to four times daily 1
• The Society for Immunotherapy of Cancer recommends 10-25 mg four times daily or at bedtime for dermatologic toxicities and pruritus 4
• Bedtime dosing (10-50 mg) is particularly effective when added to a non-sedating antihistamine regimen, as it provides nighttime symptom control while minimizing daytime sedation 2, 3
• For patients not responding to hydroxyzine alone, adding an H2-antagonist like cimetidine may improve control 2

Anxiety Management

For generalized anxiety disorder, the FDA-approved dose is 50-100 mg four times daily. 1

• Clinical trials have demonstrated efficacy at a fixed dose of 50 mg daily for GAD, with superiority over placebo beginning in the first week 5, 6
• The anxiolytic effect is maintained throughout 4 weeks of treatment without rebound anxiety upon abrupt discontinuation 6

Critical Dosing Adjustments

Renal Impairment

• Reduce dose by 50% in moderate renal impairment (creatinine clearance 10-20 mL/min) 2, 3
• Avoid completely in severe renal impairment (creatinine clearance <10 mL/min) 2

Hepatic Impairment

• Avoid hydroxyzine in severe liver disease due to enhanced sedating effects 2, 3

Elderly Patients

• Use lower doses in older adults due to increased risk of sedation and anticholinergic effects 3
• Older adults are at particularly high risk for side effects, especially with pre-existing prostatic hypertrophy, elevated intraocular pressure, or cognitive impairment 3

Important Safety Considerations

Contraindications

• Absolutely contraindicated in early pregnancy 2, 3
• If antihistamine therapy is necessary during pregnancy, chlorphenamine is preferred due to its long safety record 2

Drug Interactions

• Avoid concomitant use with other CNS depressants (benzodiazepines, opioids, alcohol) as this significantly enhances sedation and performance impairment 2, 3

Common Side Effects

• Sedation occurs in approximately 80% of patients, which is higher than diphenhydramine (50%) or promethazine (60-73%) 3
• Transient sleepiness typically appears during the first week and progressively diminishes with continued treatment 6
• Other common effects include dry mouth (14%), weight gain (12%), and loss of concentration (9%) 6

Practical Dosing Strategy

The most effective approach is bedtime dosing to minimize daytime impairment:

• Hydroxyzine 50 mg at bedtime maintains H1-receptor antagonism the following morning while alleviating the reaction time prolongation seen with divided doses 7
• This strategy provides therapeutic benefit without the significant psychomotor performance degradation documented with twice-daily dosing 8, 7
• Prolonged monotherapy is not recommended; hydroxyzine should be used as a nighttime adjunct to non-sedating antihistamines for long-term management 2, 3

Common Pitfall

Subjective symptoms of drowsiness are unreliable predictors of objective performance impairment—patients may not feel drowsy but still demonstrate prolonged reaction times 8. Therefore, warn all patients about potential impairment regardless of how they feel.