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

Maximum Hydroxyzine Dosing

The maximum recommended dose of hydroxyzine is 100 mg four times daily (400 mg/day) for adults when used for anxiety and tension, though most clinical applications use lower maximum doses. 1

Dosing by Indication

Anxiety and Tension

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

Pruritus (Allergic Conditions, Chronic Urticaria)

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

Sedation/Premedication

• Adults: 50-100 mg 1
• Children: 0.6 mg/kg of body weight 1

Nighttime Sedation for Urticaria

• Adults: 10-50 mg at night when added to a non-sedating antihistamine during the day 2

Critical Dosing Adjustments

Renal Impairment

The dose of hydroxyzine should be halved in patients with moderate renal impairment (creatinine clearance 10-20 mL/min). 2 Hydroxyzine should be avoided entirely in severe renal impairment (creatinine clearance <10 mL/min). 2

Hepatic Impairment

Hydroxyzine should be avoided in severe liver disease because its sedating effect is inappropriate and potentially dangerous in this population. 2

Pregnancy

Hydroxyzine is specifically contraindicated during early pregnancy and is the only antihistamine with this explicit contraindication in U.K. manufacturer guidelines. 2

Important Clinical Considerations

Sedation Profile

Hydroxyzine causes significant sedation, particularly at higher doses, which distinguishes it from non-sedating antihistamines. 2 The sedation typically appears during the first week of treatment and may progressively diminish with continued use. 3

Tolerance Development

Chronic daily use of hydroxyzine (75 mg/day for 3 weeks) can lead to partial tolerance, not only to hydroxyzine itself but also to clinically unrelated antihistamines. 4 This cross-tolerance phenomenon should be considered when planning long-term therapy.

Efficacy Timeline

When used for anxiety disorders at 50 mg/day, hydroxyzine produces statistically significant anxiolytic effects within the first week of treatment, with maintained efficacy throughout 4 weeks without rebound anxiety upon discontinuation. 3

Dosage Adjustment Principle

Dosage should be adjusted according to the patient's response to therapy, as emphasized in the FDA labeling. 1 When treatment is initiated intramuscularly, subsequent doses may be administered orally. 1