What is the daily maximum dose of Hydroxyzine (antihistamine) for adults with anxiety or itching, considering factors such as age, medical history, and impaired renal function?

Hydroxyzine Daily Maximum Dose

The maximum daily dose of hydroxyzine for adults is 400 mg per day (100 mg four times daily) for anxiety, or 100 mg four times daily for pruritus, with dose reductions required in elderly patients and those with renal impairment. 1

Standard Adult Dosing by Indication

For Anxiety and Tension

• Standard dose: 50-100 mg four times daily (200-400 mg total daily) 1
• This dosing is supported by clinical trial data showing efficacy at 50 mg daily for generalized anxiety disorder 2

For Pruritus (Itching/Urticaria)

• Standard dose: 25 mg three to four times daily (75-100 mg total daily) 1
• Hydroxyzine is typically used as adjunct therapy at night for urticaria rather than first-line monotherapy due to sedating properties 3

As Premedication/Sedation

• Single dose: 50-100 mg 1

Dose Adjustments for Special Populations

Elderly Patients (≥65 Years)

• Reduce dose by half due to age-related decline in renal function and increased sensitivity to central nervous system effects 3
• Elderly patients experience higher rates of CNS and gastrointestinal symptoms at standard doses 4

Renal Impairment

• Moderate renal impairment: Reduce dose by half 3
• Hydroxyzine should be avoided or used with extreme caution in severe renal dysfunction due to accumulation risk 3

Hepatic Impairment

• Severe liver disease: Avoid hydroxyzine entirely 3
• Use with caution in any degree of hepatic impairment 3

Pediatric Dosing

Children Under 6 Years

• Maximum: 50 mg daily in divided doses (for both anxiety and pruritus) 1

Children Over 6 Years

• Maximum: 50-100 mg daily in divided doses 1

Important Clinical Considerations

Side Effect Profile

• Most common adverse effect: Sedation/drowsiness, which typically appears during the first week and may diminish with continued use 2
• Other common effects include dry mouth (14%), weight gain (12%), loss of concentration (9%), and insomnia (9%) 2
• Hydroxyzine significantly prolongs reaction times without development of tolerance over 5 days of administration 5

Dosing Strategy to Minimize Side Effects

• Evening/bedtime dosing can maintain antihistamine efficacy while mitigating daytime psychomotor impairment and reaction time degradation 6
• A single 50 mg dose at bedtime provides comparable histamine suppression to divided dosing while reducing objective performance deficits 6

Contraindications and Precautions

• Pregnancy: Avoid in early pregnancy, especially first trimester 3
• Severe liver disease: Absolute contraindication 3
• Renal impairment: Requires dose reduction 3
• No evidence of organ toxicity or dependency with appropriate use 7

Lack of Tolerance Development

• Clinical experience demonstrates absence of dependency and maintained efficacy without rebound anxiety upon abrupt discontinuation after 4 weeks of treatment 2
• No withdrawal symptoms reported after stopping hydroxyzine 2