What it's for (Indications)
- Hydroxyzine is a first-generation antihistamine with sedative, anxiolytic, and antiemetic properties, primarily indicated for the symptomatic relief of anxiety and tension associated with psychoneurosis and as an adjunct in organic disease states in which anxiety is manifested.
- It is also extensively used for the symptomatic relief of pruritus due to allergic conditions, such as chronic urticaria and atopic and contact dermatoses, and in histamine-mediated pruritus.
- Furthermore, hydroxyzine can be employed as a sedative when used as a premedication and following general anesthesia, contributing to reduced agitation and requiring less narcotic medication.
- Its broad spectrum of utility makes it a versatile agent in managing various conditions where sedation or antipruritic effects are beneficial.
- The prescribing clinician must carefully evaluate the patient's specific needs and potential risks before initiating therapy.
Dosage Information
| Type | Guideline |
|---|---|
| Standard | The dosage of hydroxyzine must be individualized based on the patient's age, weight, medical condition, and response to treatment, with careful consideration given to its sedative and anticholinergic effects. For symptomatic relief of anxiety and tension, typical adult oral doses range from 50 mg to 100 mg four times daily. For pruritus, adults may receive 25 mg three to four times daily. As a sedative pre- or post-operatively, the adult dose is typically 50 mg to 100 mg. For pediatric patients, dosages are significantly lower and are typically based on weight (e.g., 0.6 mg/kg/day to 2 mg/kg/day divided into several doses for pruritus or anxiety). Intramuscular administration is also available for acute anxiety or sedation, with typical adult doses ranging from 25 mg to 100 mg. It is crucial to use the lowest effective dose for the shortest duration possible, particularly in elderly patients or those with renal or hepatic impairment, to minimize adverse effects. Dosage adjustments may be necessary to mitigate potential side effects, especially central nervous system depression and anticholinergic effects. |
Safety & Warnings
Common Side Effects
- Hydroxyzine, while generally well-tolerated at appropriate doses, can induce a range of side effects, predominantly due to its pharmacological actions.
- The most common adverse reactions include central nervous system depression, manifesting as drowsiness, sedation, somnolence, and fatigue.
- These effects are often dose-dependent and may be more pronounced at the initiation of therapy or with higher doses.
- Anticholinergic effects are also frequently reported, including dry mouth, blurred vision, constipation, and urinary retention, which can be particularly problematic in elderly patients.
- Less common, but potentially more serious, side effects involve cardiac effects, notably QT interval prolongation and, in rare instances, Torsade de Pointes.
- Other reported side effects include headache, dizziness, tremor, confusion, hallucinations (especially at higher doses or in susceptible individuals), skin rash, and hypersensitivity reactions.
- Patients should be advised against operating machinery or driving until they know how the medication affects them.
Serious Warnings
- Black Box Warning: While hydroxyzine does not carry an official FDA-mandated Black Box Warning, it is imperative to include a 'Serious Warnings' section due to significant safety concerns, particularly regarding cardiac risks. **Serious Warnings:** Hydroxyzine is associated with a risk of QT interval prolongation and Torsade de Pointes, a potentially fatal ventricular arrhythmia. This risk is dose-dependent and increased by the presence of underlying cardiac conditions, electrolyte disturbances (such as hypokalemia or hypomagnesemia), or co-administration with other drugs known to prolong the QT interval. Clinicians must thoroughly assess a patient's cardiac history, concomitant medications, and electrolyte status before initiating hydroxyzine therapy. Regular electrocardiogram (ECG) monitoring may be warranted in patients at high risk. Concomitant use of hydroxyzine with other QT-prolonging agents (e.g., certain antiarrhythmics, antipsychotics, antidepressants, antibiotics, and antifungals) is strictly contraindicated due to the significantly augmented risk of life-threatening cardiac events. Patients should be advised to report any symptoms suggestive of cardiac arrhythmia, such as palpitations, dizziness, or syncope, immediately. The lowest effective dose should always be used, and the duration of treatment should be as short as possible, especially in vulnerable populations like the elderly or those with hepatic or renal impairment, who may have altered drug metabolism and excretion, further increasing systemic exposure and cardiac risk.
- Hydroxyzine should be used with extreme caution in patients with conditions that may predispose them to QT interval prolongation, including congenital long QT syndrome, a family history of long QT syndrome, electrolyte imbalances (hypokalemia, hypomagnesemia), and pre-existing cardiac disease.
- Concomitant use with other medications known to prolong the QT interval must be avoided due to an increased risk of serious cardiac arrhythmias, including Torsade de Pointes.
- Elderly patients are particularly susceptible to anticholinergic side effects, sedation, and cognitive impairment, and should receive lower initial doses.
- Patients with hepatic or renal impairment may require dose adjustments due to altered drug metabolism and elimination.
- This medication can potentiate the effects of alcohol and other central nervous system depressants, leading to enhanced sedation and impaired cognitive function; concurrent use should be avoided or carefully monitored.
- Caution is also advised in patients with narrow-angle glaucoma, prostatic hypertrophy, or bladder neck obstruction due to its anticholinergic properties.
- Patients should be informed about potential drowsiness and advised against engaging in activities requiring mental alertness.
How it Works (Mechanism of Action)
Hydroxyzine exerts its therapeutic effects primarily through its potent antagonism of histamine H1 receptors in the central nervous system and periphery. By blocking these receptors, it effectively reduces histamine-mediated allergic responses, leading to its antipruritic actions. Beyond its antihistaminic properties, hydroxyzine also possesses significant anticholinergic activity, which contributes to its sedative and antiemetic effects, though this also accounts for many of its common side effects like dry mouth and urinary retention. It also exhibits some activity as an antagonist at 5-HT2 serotonin receptors and D2 dopamine receptors, although these contributions to its overall clinical profile are generally considered less prominent than its H1 antagonism. The anxiolytic and sedative effects are believed to stem from its central nervous system depression, potentially through its effects on subcortical areas of the brain, including the limbic system, hypothalamus, and reticular formation. This complex pharmacological profile underlies its utility in managing anxiety, pruritus, and as a pre-operative sedative.