What is the maximum recommended dose of hydroxyzine (antihistamine) for adults?

Maximum Dose of Hydroxyzine for Adults

The maximum dose of hydroxyzine for adults is 100 mg four times daily (400 mg/day total) for anxiety and tension, or 25 mg four times daily (100 mg/day total) for pruritus management. 1

FDA-Approved Maximum Dosing by Indication

The FDA label provides clear maximum dosing parameters based on clinical indication 1:

For Anxiety and Tension

• Standard dose: 50-100 mg four times daily (q.i.d.) 1
• This translates to a maximum daily dose of 400 mg/day when using the upper limit
• Dosing should be adjusted according to patient response 1

For Pruritus (Allergic Conditions)

• Standard dose: 25 mg three to four times daily (t.i.d. or q.i.d.) 1
• Maximum daily dose is 100 mg/day for this indication
• Used for chronic urticaria, atopic dermatitis, contact dermatoses, and histamine-mediated pruritus 1

For Premedication/Sedation

• Single dose: 50-100 mg 1
• Used as premedication or following general anesthesia 1

Important Dosing Modifications

Renal Impairment

• Moderate renal impairment: Reduce dose by 50% 2
• Severe renal impairment (CrCl <10 mL/min): Avoid hydroxyzine entirely 2

Hepatic Impairment

• Severe liver disease: Avoid hydroxyzine due to its sedating effects 2

Pregnancy

• Contraindicated in early pregnancy 2
• If antihistamine therapy is necessary during pregnancy, chlorphenamine is preferred 2

Clinical Considerations for Dosing Strategy

Timing to Minimize Side Effects

Research demonstrates that bedtime dosing (50 mg at night) significantly reduces psychomotor impairment while maintaining therapeutic efficacy 3. This strategy:

• Maintains H1-receptor antagonism the following morning 3
• Alleviates reaction time prolongation seen with divided doses 3
• Reduces but does not eliminate subjective symptoms like drowsiness 3

Combination Therapy

• For refractory urticaria: Add an H2-antagonist (such as cimetidine) to hydroxyzine for better control 2
• Particularly useful: Add hydroxyzine at night to a non-sedating antihistamine regimen 2

Critical Safety Warnings

CNS Depression and Driving Impairment

• Hydroxyzine produces significant CNS depressant effects including fatigue, sedation, and impaired memory 4
• Avoid concomitant use with other CNS depressants as this enhances performance impairment 2
• Studies confirm hydroxyzine significantly prolongs both simple and choice reaction times (p ≤0.0001) 5
• No tolerance develops to these objective impairments even after 5 days of use 5

Common Pitfalls

• Subjective symptoms are unreliable predictors of objective performance impairment—patients may not feel impaired despite measurable deficits 5
• The most common side effects at standard doses include drowsiness (28%), dry mouth (14%), and weight gain (12%) 6
• Sleepiness typically appears during the first week and progressively diminishes with continued treatment 6

Pharmacokinetic Profile Supporting Dosing

• Elimination half-life: 20 hours 7
• Time to peak concentration: 2.1 hours after oral administration 7
• Duration of antihistaminic effect: Wheal suppression persists 36 hours, flare suppression 60 hours after a single dose 7
• This prolonged effect supports less frequent dosing strategies 7