====== Hydroxyzine ======

Hydroxyzine is a **first-generation antihistamine** with **anxiolytic**, **sedative**, and **anticholinergic** properties. It is used in the treatment of anxiety, insomnia, pruritus, and as an adjunct in allergic and psychoneurotic conditions.

===== Classification =====
  * **Drug class:** H1-antihistamine (first-generation)
  * **ATC code:** N05BB01
  * **Subtypes:** 
    * Hydroxyzine hydrochloride (Atarax®)
    * Hydroxyzine pamoate (Vistaril®)

===== Mechanism of Action =====
  * Antagonist at **histamine H1 receptors** in the CNS and periphery
  * Also has effects on **muscarinic**, **serotonergic**, and **dopaminergic** receptors
  * Produces **sedation, anxiolysis**, and **antiemetic** effects

===== Indications =====
  * **Anxiety disorders** (short-term treatment)
  * **Preoperative sedation**
  * **Insomnia** (off-label)
  * **Urticaria** and **pruritus**
  * **Allergic rhinitis**
  * **Tinnitus-related distress** (off-label)

===== Dosage (Adults) =====
  * **Anxiety:** 25–50 mg up to 4 times daily
  * **Pruritus:** 25 mg at night or every 6–8 hours
  * **Sedation:** 50–100 mg at bedtime
  * **Titrate** based on sedation and tolerability

===== Adverse Effects =====
  * **Common:** Drowsiness, dry mouth, headache, dizziness, blurred vision
  * **Anticholinergic:** Constipation, urinary retention, confusion (especially in elderly)
  * **Rare but serious:** QT prolongation, seizures (at high doses)

===== Contraindications =====
  * Hypersensitivity to hydroxyzine or cetirizine (its active metabolite)
  * **Prolonged QT interval** or history of **torsades de pointes**
  * **First trimester of pregnancy** (teratogenic risk)

===== Precautions =====
  * Use with caution in **elderly** (Beers Criteria)
  * Avoid in **renal or hepatic impairment** without dose adjustment
  * Caution with **other CNS depressants** (alcohol, opioids, benzodiazepines)

===== Drug Interactions =====
  * **CNS depressants:** Additive sedation
  * **QT-prolonging drugs:** Increased risk of arrhythmia
  * **MAO inhibitors:** Avoid concomitant use

===== Clinical Notes =====
  * Considered a **non-addictive alternative** to benzodiazepines for anxiety or sleep
  * Onset of action: **~15–30 minutes**
  * May impair psychomotor performance; avoid driving

===== Synonyms and Brand Names =====
  * **Hydroxyzine hydrochloride:** Atarax®
  * **Hydroxyzine pamoate:** Vistaril®
  * **Metabolite:** Cetirizine (second-generation antihistamine)

===== Related Topics =====
  * [[antihistamines|Antihistamines]]
  * [[anxiolytics|Anxiolytic medications]]
  * [[insomnia|Pharmacological management of insomnia]]
  * [[tinnitus|Tinnitus and pharmacologic modulation]]