What is the maximum dose of Atarax (hydroxyzine) for a patient with psych anxiety on an as-needed basis (prn)?

Maximum PRN Dose of Hydroxyzine (Atarax) for Psychiatric Anxiety

For psychiatric anxiety on a PRN basis, hydroxyzine (Atarax) should be dosed at 50-100 mg every 6 hours as needed, with a maximum daily dose of 400 mg (100 mg four times daily). 1

Standard PRN Dosing Protocol

The FDA-approved dosing for symptomatic relief of anxiety and tension associated with psychoneurosis is 50-100 mg four times daily (q.i.d.) in adults 1. When used PRN rather than scheduled:

• Start with 50 mg PRN for mild-to-moderate anxiety episodes 1
• Use 100 mg PRN for more severe anxiety or inadequate response to lower doses 1
• Minimum interval between doses: 6 hours (based on q.i.d. dosing schedule) 1
• Maximum single dose: 100 mg 1
• Maximum daily dose: 400 mg (100 mg × 4 doses) 1

Clinical Evidence Supporting Efficacy

Hydroxyzine at 50 mg daily dosing has demonstrated superiority over placebo on all anxiety measures from the first week of treatment, with efficacy maintained throughout 4 weeks 2. In head-to-head comparison, hydroxyzine showed greater and more rapid cognitive improvement than lorazepam 2. The medication has proven effective in generalized anxiety disorder, with 66% of patients achieving excellent or good results 3.

Special Population Adjustments

Elderly or debilitated patients:

• Reduce initial dose to 25-50 mg PRN 1
• Monitor closely for sedation and anticholinergic effects
• Consider maximum daily dose of 200-300 mg rather than 400 mg

Patients with hepatic impairment:

• Start at lower end of dosing range (25-50 mg PRN) 1
• Extend dosing intervals to every 8 hours if needed

Critical Prescribing Considerations

Onset and duration of action:

• Hydroxyzine provides anxiolytic effects within 15-30 minutes of oral administration
• Duration of action is 4-6 hours, supporting q.i.d. dosing 1

Common side effects to counsel patients about:

• Transitory sleepiness (36% of patients) - most common, typically resolves with continued use 3
• Weakness (18%), headache (6%), dry mouth (2%) 3
• Rare allergic reactions including urticaria 3

Key advantages over benzodiazepines:

• No dependency or addiction potential 2
• No organ toxicity with long-term use 2
• Superior cognitive profile compared to benzodiazepines 2
• Can be discontinued abruptly without withdrawal syndrome 2

Practical PRN Prescribing Strategy

For acute anxiety episodes:

• Write prescription as: "Hydroxyzine 50-100 mg PO every 6 hours as needed for anxiety, maximum 400 mg per 24 hours" 1
• Instruct patients to start with 50 mg and increase to 100 mg if inadequate response after 30-60 minutes 1
• Advise against driving or operating machinery until individual response is known due to sedation risk 3

Common pitfall to avoid: Do not combine hydroxyzine with other CNS depressants (benzodiazepines, opioids, alcohol) without careful monitoring, as this potentiates sedation 1. Unlike benzodiazepines, hydroxyzine does not carry the same respiratory depression risk, but sedation is additive 2.