Maximum Daily Dosage of Hydroxyzine
The maximum daily dosage of hydroxyzine for adults is 400 mg per day, divided into multiple doses throughout the day.
Dosing Guidelines by Age Group and Indication
Hydroxyzine dosing varies based on age and clinical indication:
Adults
- Anxiety/Tension: 50-100 mg four times daily (maximum 400 mg/day) 1
- Pruritus/Allergic Conditions: 25 mg three to four times daily (maximum 100 mg/day) 1
- Premedication/Post-anesthesia Sedation: 50-100 mg per dose 1
Children
- Under 6 years: 50 mg daily in divided doses 1
- Over 6 years: 50-100 mg daily in divided doses 1
- Premedication: 0.6 mg/kg of body weight 1
Clinical Considerations
Dosing Adjustments
- Renal Impairment: The dose should be halved in moderate renal impairment 2
- Severe Renal Impairment: Hydroxyzine should be avoided in severe renal impairment (creatinine clearance <10 mL/min) 2
- Hepatic Impairment: Should be avoided in severe liver disease due to its sedating effects 2
Administration Timing
- Evening dosing may help mitigate daytime sedation while maintaining therapeutic effects
- Studies show that bedtime dosing (50 mg qhs) maintains skin H1-receptor antagonism the following morning while reducing daytime drowsiness 3
Side Effect Profile
- Common side effects: Drowsiness (28%), dry mouth (14%), weight gain (12%) 4
- Sedation is typically most pronounced during the first week of treatment and often diminishes with continued use 4
- Higher doses increase risk of sedation and anticholinergic effects
Special Populations
Pregnancy
- Contraindicated during early pregnancy according to UK manufacturer's Summary of Product Characteristics 2
- Should be avoided if possible throughout pregnancy, especially during the first trimester 2
Elderly
- Lower doses are generally recommended due to increased sensitivity to anticholinergic and sedative effects
- Start at the lower end of the dosing range and titrate based on response and tolerability
Clinical Efficacy
- Effective for anxiety at doses as low as 50 mg/day in clinical trials 4, 5
- For allergic conditions, doses up to 150 mg/day have shown efficacy in seasonal allergic rhinitis 6
Important Precautions
- Hydroxyzine has significant sedative properties that may impair driving and operation of machinery
- Avoid concurrent use with other CNS depressants when possible
- Tolerance to the antihistamine effects may develop with prolonged use 7
- Dosage should be adjusted according to individual patient response 1
When prescribing hydroxyzine, always consider the specific indication, patient age, comorbidities, and potential for drug interactions to determine the most appropriate dosing regimen within the maximum daily limit of 400 mg for adults.