What is the dosage and usage of Hydroxyzine for treating itching and allergic reactions?

Hydroxyzine Dosage and Usage for Treating Itching and Allergic Reactions

For treating pruritus (itching) due to allergic conditions, hydroxyzine is dosed at 25 mg three to four times daily for adults, 50 mg daily in divided doses for children under 6 years, and 50-100 mg daily in divided doses for children over 6 years. 1

Adult Dosing for Pruritus and Allergic Conditions

• Standard adult dosage: 25 mg three to four times daily 1
• For nighttime pruritus: 25-100 mg at bedtime (particularly effective due to sedative effects) 2
• For chronic urticaria and dermatoses: 10-25 mg four times daily or at bedtime 3

Pediatric Dosing

• Children under 6 years: 50 mg daily in divided doses 1
• Children over 6 years: 50-100 mg daily in divided doses 1
• Note: In children with atopic dermatitis, a dose of 0.7 mg/kg three times daily has been shown to be as effective as higher doses with less sedation 4

Clinical Applications

Dermatologic Conditions Where Hydroxyzine is Indicated:

• Chronic urticaria
• Atopic dermatitis
• Contact dermatoses
• Histamine-mediated pruritus 1

Severity-Based Dosing:

• Mild pruritus (Grade 1): Hydroxyzine 10-25 mg four times daily or at bedtime 3
• Moderate pruritus (Grade 2): Hydroxyzine 10-25 mg four times daily or at bedtime, may be combined with topical treatments 3
• Severe pruritus (Grade 3): Consider alternative or additional therapies such as systemic corticosteroids 3

Important Considerations and Precautions

Sedation and CNS Effects

• Significant potential for sedation, drowsiness, and performance impairment 2
• Avoid morning dosing due to prolonged half-life (mean 7.1 hours) and potential for daytime drowsiness 2, 4
• Consider as a nighttime option when sedation is beneficial 2

Special Populations

1. Elderly patients:

   • Require reduced dosing
   • More sensitive to psychomotor impairment
   • Increased risk for falls, fractures
   • More susceptible to anticholinergic effects 2

2. Patients with liver disease:

   • Start with half the standard dose
   • Monitor for side effects 2

3. Patients with renal impairment:

   • Dose adjustment required 2

4. Children:

   • May experience impaired learning and school performance
   • Lower doses (0.7 mg/kg three times daily) may be as effective as higher doses with fewer side effects 4

Adverse Effects

• Dry mouth and eyes
• Constipation
• Urinary retention
• Increased risk for narrow-angle glaucoma 2
• Somnolence (reported in 40% of patients taking hydroxyzine vs. 5% with newer antihistamines) 5

Alternative Options

For patients who cannot tolerate hydroxyzine's sedative effects:

• Second-generation antihistamines: Cetirizine 10 mg daily, loratadine 10 mg daily 3, 6
• For generalized pruritus without rash: Consider gabapentin, pregabalin, or paroxetine 3

Clinical Pearls

1. Hydroxyzine is particularly useful for nighttime pruritus due to its sedative properties.

2. Avoid using hydroxyzine in patients with known sensitivity to ethylenediamine as it may worsen contact dermatitis in these individuals 7.

3. In real-world settings, hydroxyzine has shown significant improvement in pruritus symptoms and quality of life over a 12-week period 8.

4. For allergy testing, discontinue hydroxyzine 7-10 days before the procedure 2.

5. When treating chronic pruritus, consider combination therapy with topical corticosteroids and emollients for enhanced effect 3.