What is the recommended dosing for hydroxyzine (an antihistamine)?

Hydroxyzine Dosing

For adults with pruritus or allergic conditions, hydroxyzine should be dosed at 25 mg three to four times daily, or alternatively 10-50 mg at bedtime when used as a sedating antihistamine adjunct to daytime non-sedating antihistamines. 1, 2

Standard Adult Dosing by Indication

Pruritus and Allergic Conditions

• 25 mg three to four times daily (TID or QID) is the FDA-approved dose for managing pruritus due to chronic urticaria, atopic dermatitis, and contact dermatoses 1
• 10-50 mg at bedtime is recommended by the British Journal of Dermatology as an adjunct to non-sedating antihistamines taken during the day, particularly beneficial for patients with urticaria who need improved sleep 2, 3
• For mild to moderate itching, 10 mg every 6 hours as needed can be used for 2-4 weeks 2

Anxiety and Tension

• 50-100 mg four times daily (QID) for symptomatic relief of anxiety associated with psychoneurosis or organic disease states 1
• Clinical trials demonstrate significant anxiolytic effects at 50 mg/day, with benefits appearing within the first week and maintained throughout 4 weeks of treatment 4

Preoperative Sedation

• 50-100 mg as a single dose when used as premedication or following general anesthesia 1

Pediatric Dosing

• Children under 6 years: 50 mg daily in divided doses for both pruritus and anxiety indications 1
• Children over 6 years: 50-100 mg daily in divided doses 1
• Optimal pediatric dose for atopic dermatitis: 0.7 mg/kg three times daily provides effective pruritus suppression (>85% suppression for 2-12 hours) with significantly less sedation than higher doses 5

Dose Adjustments and Special Populations

Renal Impairment

• Moderate renal insufficiency (creatinine clearance 10-20 mL/min): Reduce dose by half 2, 3
• Severe renal impairment (creatinine clearance <10 mL/min): Avoid hydroxyzine 3

Hepatic Impairment

• Severe hepatic disease: Avoid hydroxyzine due to enhanced sedative effects 2, 3

Elderly Patients

• Use lower doses due to increased sensitivity to psychomotor impairment and anticholinergic effects 2, 6
• The Journal of Allergy and Clinical Immunology notes that older adults are at high risk for side effects from first-generation antihistamines, particularly with pre-existing conditions like prostatic hypertrophy, elevated intraocular pressure, or cognitive impairment 7
• Consider second-generation antihistamines (fexofenadine, loratadine, desloratadine) as safer alternatives 6

Dosing Strategy to Minimize Side Effects

Evening or bedtime dosing (50 mg at bedtime) significantly reduces daytime psychomotor impairment while maintaining antihistamine efficacy. 8

• Research demonstrates that hydroxyzine 25 mg twice daily significantly prolongs reaction times and causes drowsiness, dry mouth, and irritability 9
• Bedtime dosing of 50 mg eliminates reaction time degradation seen with divided doses while maintaining histamine skin test suppression the following morning 8
• This strategy preserves the pharmacokinetic and cost advantages of first-generation antihistamines while mitigating adverse effects 8

Duration of Treatment

• Avoid extended monotherapy with hydroxyzine; favor use as a nighttime adjunct to non-sedating antihistamines for long-term management 2
• For acute symptoms, 2-4 weeks is appropriate 2
• Transition to second-generation antihistamines for chronic conditions requiring prolonged treatment 2
• No tolerance develops to sedative or performance effects even after 5 days of continuous use 9

Critical Contraindications and Precautions

• Contraindicated in early pregnancy 2, 3; if antihistamine therapy is necessary during pregnancy, chlorphenamine is preferred 3
• Avoid concomitant use with other CNS depressants (including alcohol, benzodiazepines, opioids) as this enhances performance impairment and sedation 7, 3
• Do not combine with benzodiazepines when treating depression, as benzodiazepines may antagonize the effects of SSRIs; hydroxyzine does not interfere with SSRI efficacy 10
• Hydroxyzine causes 80% sedation rates compared to 50% with diphenhydramine and 60-73% with promethazine 7

Clinical Pearls

• Subjective symptoms are unreliable predictors of objective performance impairment—patients may not feel drowsy but still have prolonged reaction times 9
• For steroid-refractory pruritus in immune checkpoint inhibitor toxicity, hydroxyzine 10-25 mg QID or at bedtime can be combined with topical corticosteroids 7
• Adding an H2-antagonist (cimetidine) may provide better control in urticaria not responding to hydroxyzine alone 3
• The anticholinergic effects of hydroxyzine provide better control of rhinorrhea compared to second-generation antihistamines 7