Hydroxyzine: Uses, Dosage & Side Effects

What Is Hydroxyzine and What Is It Used For?

Hydroxyzine hydrochloride is a first-generation antihistamine belonging to the piperazine class of compounds. First synthesised in the 1950s, it has been used clinically for decades and remains an important pharmacological tool in the management of anxiety and pruritus. Unlike most other first-generation antihistamines, hydroxyzine is distinguished by its dual clinical utility: it functions both as an effective antipruritic agent through peripheral H1 receptor blockade and as an anxiolytic through its effects on the central nervous system.

The anxiolytic properties of hydroxyzine are thought to arise from its ability to suppress activity in certain subcortical regions of the brain, including portions of the reticular activating system. This central nervous system depression produces a calming effect without the euphoria, reinforcement, or physical dependence associated with benzodiazepines or barbiturates. This non-addictive profile makes hydroxyzine a particularly valuable option for patients with anxiety who have a history of substance use disorder or for those in whom benzodiazepines are considered inappropriate.

For anxiety, hydroxyzine is approved for use in adults and provides symptomatic relief within 30 to 45 minutes of oral administration. It is typically used for short-term management of generalised anxiety, pre-operative anxiety, or as an adjunct to other anxiolytic treatments. While it is not a first-line treatment for anxiety disorders according to most international guidelines (which favour selective serotonin reuptake inhibitors and cognitive behavioural therapy), hydroxyzine offers a useful alternative in situations where rapid symptom relief is needed without the risks associated with controlled substances.

For pruritus (itching), hydroxyzine is approved for adults, adolescents, and children from 6 years of age. The antipruritic effect is mediated primarily through antagonism of histamine H1 receptors at peripheral sites, combined with sedative properties that can help patients whose itching disrupts sleep. Hydroxyzine is used for various causes of pruritus, including allergic dermatitis, urticaria (hives), eczema-associated itching, and pruritus of unknown origin. Symptom relief for itching typically occurs within approximately 1 hour of ingestion.

How Hydroxyzine Works

Hydroxyzine exerts its pharmacological effects through multiple receptor-mediated mechanisms. Its primary action is competitive antagonism of histamine H1 receptors. By blocking these receptors in peripheral tissues, hydroxyzine suppresses the effects of histamine release during allergic reactions, including vasodilation, increased capillary permeability, smooth muscle contraction, and sensory nerve stimulation that causes itching.

In addition to its antihistaminic activity, hydroxyzine possesses anticholinergic (antimuscarinic) properties, which contribute to side effects such as dry mouth, urinary retention, and blurred vision. It also exhibits antiserotonergic activity, antagonising 5-HT2A receptors, which may contribute to its anxiolytic and sedative effects. The combined action on multiple neurotransmitter systems produces the characteristic profile of sedation, anxiolysis, and antipruritic activity.

Hydroxyzine is rapidly and completely absorbed from the gastrointestinal tract after oral administration, with peak plasma concentrations reached within approximately 2 hours. It is extensively metabolised in the liver, primarily via the cytochrome P450 enzymes CYP3A4 and CYP3A5. The principal active metabolite is cetirizine, a second-generation antihistamine that is itself widely used as a standalone medication for allergic conditions. The elimination half-life of hydroxyzine is approximately 14 hours in healthy adults, though this may be prolonged in elderly patients (up to 29 hours) and those with hepatic impairment.

What Should You Know Before Taking Hydroxyzine?

Contraindications

Hydroxyzine has a significant number of contraindications compared to many other antihistamines, primarily due to its cardiovascular safety profile. The medication must not be taken in the following situations:

• Hypersensitivity — allergy to hydroxyzine hydrochloride, cetirizine (the active metabolite), aminophylline, ethylenediamine, piperazine derivatives, or any excipient in the formulation.
• Porphyria — a group of metabolic disorders affecting haem biosynthesis. Hydroxyzine may exacerbate porphyric crises.
• QT prolongation — patients whose electrocardiogram (ECG) shows a prolonged QT interval must not take hydroxyzine due to the risk of fatal cardiac arrhythmias.
• Cardiovascular disease — patients with current or prior cardiovascular disease, including heart failure, coronary artery disease, or cardiomyopathy.
• Bradycardia — patients with very slow heart rate.
• Electrolyte imbalances — low blood levels of potassium (hypokalaemia) or magnesium (hypomagnesaemia), as these conditions increase the risk of QT prolongation and cardiac arrhythmias.
• Concomitant QT-prolonging medications — hydroxyzine must not be used simultaneously with other drugs known to prolong the QT interval (see Drug Interactions section).
• Family history of sudden cardiac death — patients with a family history of sudden cardiac death should not take hydroxyzine.
• Pregnancy and breastfeeding — hydroxyzine crosses the placenta and passes into breast milk (see Pregnancy and Breastfeeding section).

Warnings and Precautions

Several clinical situations require special caution and possibly dose adjustment when using hydroxyzine. Patients should discuss any of the following conditions with their prescribing physician:

• Kidney disease — hydroxyzine's active metabolite (cetirizine) is primarily eliminated through the kidneys. Patients with moderate or severe renal impairment require dose reduction to prevent drug accumulation.
• Liver disease — since hydroxyzine is extensively metabolised in the liver, impaired hepatic function can lead to increased drug levels and prolonged duration of action. A daily dose reduction is recommended.
• Elderly patients — the elderly are more susceptible to the central nervous system effects of hydroxyzine, including excessive sedation, confusion, and falls. The initial dose should be halved, and the maximum daily dose should not exceed 50 mg.
• Seizure disorder — hydroxyzine may lower the seizure threshold. Patients with epilepsy or a history of seizures should be closely monitored.
• Stroke risk factors — patients with risk factors for cerebrovascular events should exercise caution.
• Glaucoma — the anticholinergic effects of hydroxyzine may increase intraocular pressure, potentially worsening angle-closure glaucoma.
• Urinary obstruction — anticholinergic effects may exacerbate urinary retention in patients with prostatic hyperplasia or other urinary tract obstructions.
• Constipation — anticholinergic effects can reduce gastrointestinal motility, worsening constipation or ileus.
• Myasthenia gravis — hydroxyzine may worsen muscle weakness in patients with this neuromuscular disorder.
• Dementia — anticholinergic medications may worsen cognitive function in patients with dementia.

Pregnancy and Breastfeeding

Hydroxyzine is contraindicated during pregnancy. The active substance crosses the placental barrier and may adversely affect the developing foetus. Animal studies have shown teratogenic effects, and although controlled human studies are limited, the precautionary principle applies. Neonatal adverse effects have been observed in newborns whose mothers used hydroxyzine during late pregnancy or during labour, including tremors, muscle rigidity and/or weakness, respiratory difficulties, and urinary retention. These symptoms were observed immediately or within a few hours after birth.

Hydroxyzine is also contraindicated during breastfeeding. The drug and its metabolites, including cetirizine, are excreted into breast milk at clinically significant concentrations. If hydroxyzine treatment is deemed medically necessary, breastfeeding must be discontinued. Women of childbearing potential should use effective contraception during treatment, and the medication should be stopped if pregnancy is suspected or confirmed.

Driving and Operating Machinery

Hydroxyzine may significantly impair the ability to drive and operate machinery. It can cause drowsiness, decreased attention, and reduced reaction time. These effects are most likely to occur at the beginning of treatment or when the dose is increased. Patients should not drive or operate heavy machinery until they have fully assessed how hydroxyzine affects them individually. The combination of hydroxyzine with alcohol or other central nervous system depressants can dramatically amplify these effects.

Excipients

Hydroxyzine film-coated tablets typically contain lactose monohydrate as an excipient. Patients with rare hereditary conditions of galactose intolerance, total lactase deficiency, or glucose-galactose malabsorption should not take these formulations and should inform their prescribing physician. The tablets also contain less than 1 mmol (23 mg) sodium per tablet, making them essentially sodium-free.

Children

Hydroxyzine film-coated tablets are not recommended for children under 6 years of age, as younger children may have difficulty swallowing tablets. The medication should not be used in children under 12 months, as it has not been studied in this age group. Younger children are more susceptible to central nervous system side effects, particularly seizures. For itching in children aged 6 years and older, hydroxyzine may be prescribed at a weight-based dose determined by the treating physician.

How Does Hydroxyzine Interact with Other Drugs?

Hydroxyzine's drug interaction profile is broader and more clinically significant than that of second-generation antihistamines. This is due to its central nervous system activity, anticholinergic properties, and most critically, its potential to prolong the QT interval. Understanding these interactions is essential for safe use of this medication.

The most dangerous interactions involve drugs that also prolong the QT interval. When two or more QT-prolonging agents are combined, the risk of developing Torsades de Pointes, a potentially fatal ventricular tachycardia, increases substantially. For this reason, hydroxyzine is absolutely contraindicated in combination with several classes of medications detailed below.

Hydroxyzine is metabolised primarily by the cytochrome P450 enzyme CYP3A4 in the liver. Drugs that inhibit this enzyme may increase hydroxyzine plasma levels and prolong its duration of action, potentially increasing the risk of adverse effects including QT prolongation.

Contraindicated Combinations

Significant Interactions Requiring Caution

Food and Alcohol Interactions

Alcohol should be completely avoided while taking hydroxyzine. The combination of hydroxyzine and alcohol produces synergistic central nervous system depression, significantly enhancing sedation, cognitive impairment, and psychomotor dysfunction. This interaction is more pronounced than with second-generation antihistamines and poses a substantial risk for falls, motor vehicle accidents, and other injuries.

Hydroxyzine can be taken with or without food. Food does not significantly affect the absorption or bioavailability of hydroxyzine. The tablets should be swallowed whole with a sufficient amount of water.

What Is the Correct Dosage of Hydroxyzine?

Hydroxyzine dosing is individualised by the prescribing physician based on the indication, severity of symptoms, patient weight, age, and the presence of any conditions that may affect drug metabolism or elimination. The fundamental principle with hydroxyzine is to use the lowest effective dose for the shortest possible treatment duration. This approach minimises the risk of adverse effects, particularly cardiovascular risks associated with higher doses.

Adults — Anxiety

The standard regimen for anxiety in adults is 50 mg daily, divided into three separate doses: half a 25 mg tablet (12.5 mg) in the morning, half a tablet (12.5 mg) in the afternoon, and one whole 25 mg tablet at bedtime. The larger evening dose accounts for the sedative properties of hydroxyzine, which are beneficial for patients with anxiety-related sleep disturbance. In more severe cases, the daily dose may be increased to up to 100 mg per day, but this should only be done under close medical supervision and with consideration of the cardiovascular risks associated with higher doses.

Treatment of anxiety with hydroxyzine should always be considered a supportive measure and not a substitute for definitive treatment. Most international guidelines recommend cognitive behavioural therapy and/or selective serotonin reuptake inhibitors (SSRIs) as first-line treatments for generalised anxiety disorder. Hydroxyzine is best suited for short-term symptomatic relief or as an adjunct to established therapies. Patients should not adjust their dose without consulting their prescribing physician.

Adults — Pruritus (Itching)

For the management of itching, the recommended starting dose is 25 mg taken approximately 1 hour before bedtime. This evening dosing takes advantage of the sedative properties of hydroxyzine, which can help patients whose itching is particularly troublesome at night. If symptoms persist during the day, additional doses of up to 25 mg may be taken three to four times daily, with a total maximum daily dose of 100 mg. As with anxiety treatment, the guiding principle is to use the lowest effective dose.

Children ≥6 Years — Pruritus

Hydroxyzine is approved for the treatment of itching in children aged 6 years and older. The recommended dose is 1 to 2 mg/kg/day, divided into multiple dosing occasions throughout the day. For children weighing more than 40 kg, the maximum daily dose is 100 mg. For children weighing 40 kg or less, the maximum daily dose is 2 mg/kg/day. Hydroxyzine is not approved for the treatment of anxiety in children. If a child has difficulty swallowing tablets, the prescribing physician should consider alternative formulations containing hydroxyzine, such as oral solutions.

Elderly Patients

Elderly patients are particularly sensitive to the effects of hydroxyzine due to age-related changes in drug metabolism and elimination. The elimination half-life is prolonged in this population (up to 29 hours compared to approximately 14 hours in younger adults), leading to greater drug accumulation. The initial dose should be half the recommended adult dose, and the maximum daily dose must not exceed 50 mg. Treatment duration should be kept as short as possible. Elderly patients should be monitored closely for excessive sedation, confusion, falls, and anticholinergic side effects.

Missed Dose

If you forget to take a dose of hydroxyzine, take it as soon as you remember, unless it is nearly time for your next scheduled dose. In that case, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to compensate for a forgotten tablet, as this increases the risk of side effects and QT prolongation.

Overdose

Symptoms of hydroxyzine overdose may include severe drowsiness, nausea, vomiting, involuntary motor activity, impaired consciousness, cardiac arrhythmias, hypotension, and respiratory depression. Treatment is supportive and symptomatic, as there is no specific antidote. Continuous ECG monitoring is essential due to the risk of QT prolongation and associated cardiac arrhythmias. Gastric lavage may be considered if the overdose is recent and the patient is fully conscious.

What Are the Side Effects of Hydroxyzine?

Like all medications, hydroxyzine can cause side effects, although not everyone who takes it will experience them. The side effect profile of hydroxyzine reflects its pharmacological properties: its antihistaminic, anticholinergic, and central nervous system depressant actions all contribute to the range of possible adverse effects. Drowsiness is by far the most frequently reported effect and is often the dose-limiting factor in clinical practice.

Side Effects Reported with Unknown Frequency

The following side effects have been reported during post-marketing surveillance, but their exact frequency cannot be determined from available data:

• Thrombocytopenia — decreased platelet count, which may lead to easy bruising or bleeding
• Aggression
• Depression
• Tics — repetitive involuntary muscle movements
• Dystonia — abnormal prolonged muscle contractions
• Paraesthesia — tingling, prickling, or numbness sensations
• Syncope — fainting
• Oculogyric crisis — uncontrolled rolling eye movements
• QT prolongation and Torsades de Pointes — potentially life-threatening cardiac arrhythmias
• Diarrhoea
• Hepatitis — liver inflammation
• Pemphigoid — blistering skin condition
• Toxic epidermal necrolysis — severe skin damage with peeling
• Enuresis — bedwetting or urinary incontinence
• Asthenia — extreme weakness or fatigue
• Oedema — tissue swelling due to fluid retention
• Weight gain

Dry Mouth and Oral Health

Dry mouth (xerostomia) is a common side effect of hydroxyzine due to its anticholinergic properties. Chronic dry mouth can increase the risk of dental caries, gum disease, and oral infections. Patients should maintain good oral hygiene during treatment, use sugar-free drinks or chewing gum to stimulate saliva production, and attend regular dental check-ups. If dry mouth is severe or persistent, discuss management options with your healthcare provider or dentist.

Reporting Side Effects

It is important to report suspected side effects after a medication has been authorised for use. Reporting helps regulatory agencies continuously monitor the benefit-risk balance of medicines. In the United Kingdom, adverse reactions can be reported to the MHRA through the Yellow Card Scheme. In the United States, reports can be filed with the FDA through the MedWatch programme. In the European Union, national pharmacovigilance systems accept reports from both healthcare professionals and patients.

How Should You Store Hydroxyzine?

Hydroxyzine film-coated tablets should be kept out of the sight and reach of children at all times. The medication should be stored at room temperature; no special temperature requirements apply for either blister pack or bottle formulations. However, the tablets are moisture-sensitive and should be stored in their original packaging to protect against humidity. Do not transfer tablets to a separate container unless it provides equivalent protection from moisture.

Do not use hydroxyzine after the expiry date stated on the carton, blister, or bottle packaging. The expiry date refers to the last day of the indicated month. Expired medications may have reduced efficacy and potentially altered safety profiles. Unused or expired medications should never be disposed of via household waste or flushed down the toilet, as pharmaceutical residues can contaminate water supplies. Return unused medicines to a pharmacy for proper disposal through established take-back programmes.

What Does Hydroxyzine Contain?

Active Ingredient

The active pharmaceutical ingredient is hydroxyzine hydrochloride, available in two strengths: 10 mg and 25 mg per film-coated tablet. Hydroxyzine hydrochloride is the hydrochloride salt of hydroxyzine, a piperazine derivative with the chemical name 2-[2-[4-(p-chloro-alpha-phenylbenzyl)-1-piperazinyl]ethoxy]ethanol dihydrochloride. It appears as a white or almost white crystalline powder that is very soluble in water. Hydroxyzine is metabolised in the liver to its active metabolite cetirizine, which itself is a widely used second-generation antihistamine.

Inactive Ingredients (Excipients)

The inactive ingredients in hydroxyzine film-coated tablets typically include:

• Microcrystalline cellulose — a filler and binder that provides structural integrity to the tablet
• Lactose monohydrate — a filler; patients with galactose intolerance or lactase deficiency should consult their physician
• Croscarmellose sodium — a disintegrant that helps the tablet break apart in the gastrointestinal tract for rapid absorption
• Colloidal anhydrous silica — a glidant that improves powder flow during manufacturing
• Talc — an anti-adherent used in the manufacturing process
• Magnesium stearate — a lubricant that prevents the tablet from sticking to manufacturing equipment
• Hypromellose (HPMC) — forms the film coating of the tablet, providing a smooth surface for swallowing
• Macrogol 400 — a plasticiser used in the film coating to improve flexibility
• Titanium dioxide (E171) — a white colouring agent used in the film coating

Appearance

Hydroxyzine 10 mg film-coated tablets are white to off-white, round, biconvex tablets. Hydroxyzine 25 mg film-coated tablets are white to off-white, oblong (capsule-shaped), biconvex tablets with a score line on both sides. The 25 mg tablet can be divided into two equal halves of 12.5 mg each, which is useful for dose titration and for patients requiring lower doses, such as elderly patients or those initiating treatment for anxiety. Tablets are available in blister packs and bottles with child-resistant closures, with various pack sizes ranging from 20 to 250 tablets.

References

This article is based on the following international medical guidelines, regulatory documents, and peer-reviewed sources:

1. European Medicines Agency (EMA). Summary of Product Characteristics — Hydroxyzine hydrochloride film-coated tablets. Updated 2024. Available from: www.ema.europa.eu
2. U.S. Food and Drug Administration (FDA). Vistaril (hydroxyzine pamoate) and Atarax (hydroxyzine hydrochloride) — Drug Label Information. Available from: www.accessdata.fda.gov
3. World Health Organization (WHO). WHO Model List of Essential Medicines — 23rd List (2023). Geneva: World Health Organization; 2023.
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5. National Institute for Health and Care Excellence (NICE). Generalised anxiety disorder and panic disorder in adults: management. Clinical guideline [CG113]. Updated 2024. Available from: www.nice.org.uk/guidance/cg113
6. British National Formulary (BNF). Hydroxyzine hydrochloride monograph. National Institute for Health and Care Excellence (NICE). Available from: bnf.nice.org.uk
7. Pharmacovigilance Risk Assessment Committee (PRAC). Assessment report: Hydroxyzine-containing medicinal products. EMA/145085/2015. European Medicines Agency; 2015.
8. Simons FER, Simons KJ. Histamine and H1-antihistamines: celebrating a century of progress. J Allergy Clin Immunol. 2011;128(6):1161-1174. doi:10.1016/j.jaci.2011.09.005
9. Llorca PM, et al. Efficacy and safety of hydroxyzine in the treatment of generalized anxiety disorder: a 3-month double-blind study. J Clin Psychiatry. 2002;63(11):1020-1027.
10. Guaiana G, et al. Hydroxyzine for generalised anxiety disorder. Cochrane Database Syst Rev. 2010;(12):CD006815. doi:10.1002/14651858.CD006815.pub2

Editorial Team

Last medical review: January 23, 2026 | Next scheduled review: July 2026