Hydroxyzinum

Quick links to important sections

Medically reviewed

Rosario Oropesa

Last updated on 22/12/2025

This page provides general, reference-level information compiled from official medical sources. It is not a substitute for professional medical advice, diagnosis, or treatment. For decisions about your health, please consult a qualified healthcare professional.

Overview of Hydroxyzinum

Property Description
Active Ingredient Hydroxyzine
Forms Tablet, Capsule, Oral Solution, Liquid for Injection
Pharmacological Class First-Generation Antihistamine, Miscellaneous Anxiolytic
General Purpose Relieves itching and provides sedation
Origin/Type Synthetic, Piperazine derivative

Defining Hydroxyzinum: Class and Origin

Hydroxyzinum is the international non-proprietary name (INN) for the active substance Hydroxyzine, which is professionally classified as a first-generation antihistamine and a miscellaneous anxiolytic. This medication is a synthetic compound derived from the piperazine chemical class. Its primary action involves blocking the histamine H1-receptor, a mechanism that is clinically recognized for effectively suppressing symptoms of allergic hypersensitivity. This dual classification—antihistamine plus anxiolytic—is a key differentiator from modern, non-sedating antihistamines.

Composition and Available Forms

The core of the medicine is the single active ingredient, Hydroxyzine, which is typically prepared using one of two salts: Hydroxyzine hydrochloride or Hydroxyzine pamoate. Hydroxyzine is available in diverse pharmaceutical preparations, including oral dosage forms such as tablets, capsules, and an oral solution or suspension, as well as a sterile liquid for intramuscular injection. This allows for administration via the oral or intramuscular route. This wide range of forms provides the flexibility required for use in both routine outpatient care and specific pre-procedural needs.

General Purpose and Effects

The general purpose of Hydroxyzinum is to relieve intense itching (pruritus) associated with allergic skin reactions and to promote sedation for the short-term management of anxiety. Hydroxyzine achieves its effects by simultaneously blocking histamine activity and decreasing activity in specific subcortical regions of the central nervous system. This combined action is why the drug is frequently utilized for premedication before procedures when generalized relaxation is needed. The medication is also utilized to help reduce feelings of nausea due to its established antiemetic properties.

Regulatory References

  1. NIH, MedlinePlus

What side effects are possible with Hydroxyzinum?

Possible Side Effects and Safety Information

The safety profile of hydroxyzine is defined by common, generally transient side effects, and rare, but serious, cardiac risks that necessitate specific restrictions from governmental regulatory authorities.


Adverse Reactions and Frequency

The most Common adverse reactions are related to the drug's effect on the central nervous system and its anticholinergic properties, including drowsiness (usually transitory, often subsiding after a few days of continued use) and dry mouth.

Other reported effects involve the gastrointestinal and nervous systems. In Rare instances or through postmarketing reports, involuntary motor activity (e.g., tremor, convulsions, typically at higher doses), hallucination, confusion, and headache have occurred.

Serious Safety Concerns and Contraindications

Hydroxyzine is associated with a risk of QT interval prolongation and Torsades de pointes, a potentially life-threatening cardiac arrhythmia. Due to this risk, the medicine is contraindicated in patients with a known acquired or congenital prolonged QT interval or other risk factors for QT prolongation (e.g., significant electrolyte imbalance, cardiovascular disease, recent heart attack). It is also contraindicated for use with other medications known to prolong the QT interval.

Rare, serious dermatological reactions, such as Acute Generalized Exanthematous Pustulosis (AGEP), have also been reported.

Population-Specific Safety

  • Elderly Patients: Use is generally not recommended due to reduced elimination and increased susceptibility to anticholinergic effects, confusion, over-sedation, and cardiac risks. If used, the total daily dose must be restricted (e.g., maximum 50 mg/day as per EMA recommendations).
  • Pregnancy/Breastfeeding: The drug is contraindicated in early pregnancy, and use is not recommended in nursing mothers as it may be excreted in human milk.

Regulatory measures stress using the lowest effective dose for the shortest possible duration to mitigate risk, especially concerning cardiac safety.

Overdose and Emergency Response

Overdose and When to Seek Help

Overdose involving Hydroxyzine is primarily characterized by effects on the central nervous and cardiovascular systems. Officially documented manifestations often include signs of profound Central Nervous System (CNS) depression, such as hypersedation, stupor, and potentially coma or seizures. Anticholinergic toxicity presents through symptoms like blurred vision, dry mouth, and difficulty urinating. Regulatory sources note that paradoxical CNS excitation, presenting as agitation or tremor, may occur in some patients, particularly children.

The most critical and potentially life-threatening complication is the cardiovascular risk. Overdose significantly increases the likelihood of QT interval prolongation, which can lead to severe ventricular arrhythmias, including Torsade de Pointes. Respiratory depression and marked hypotension are also documented as severe outcomes.

Because no specific antidote is known for Hydroxyzine, management focuses exclusively on symptomatic and supportive treatment. Immediate medical attention must be sought upon suspected overdose. Regulatory guidance mandates urgent contact with emergency services for life-threatening symptoms, such as trouble breathing or loss of consciousness. Continuous hospital-level observation and ECG monitoring are required to manage and mitigate the documented severe cardiac risks.

Therapeutic Uses of Hydroxyzinum

What Hydroxyzinum Treats: Main Uses and Benefits

The primary therapeutic applications of Hydroxyzinum are focused on situations where short-term symptomatic assistance is needed for acute distress or discomfort, and the medication is commonly used to help manage symptoms across multiple relevant therapeutic areas.

This medication is considered relevant in conditions characterized by symptoms related to inflammatory or irritative states and acute or disruptive symptom patterns. Its uses cover symptomatic relief for chronic urticaria and other dermatoses, managing nervousness and apprehension, and providing support during clinical procedures. The medication is applied in scenarios where patients experience disruptive physical symptoms (like itching or nausea) alongside emotional tension, offering a calming, supportive effect that contributes to general well-being.

Quick Facts on Therapeutic Domains

  • Symptom Management: Helps ease the overall symptom burden associated with intense itching, anxiety, and procedural apprehension.
  • Clinical Context: Applied when short-term symptomatic assistance is needed for episodes of heightened discomfort or tension.

Eligibility and Restrictions for Use

Who can and cannot use Hydroxyzinum? — Official Regulatory Information

The eligibility profile for Hydroxyzinum is defined by specific cardiac, allergic, and physiological restrictions as stated in official regulatory documents.

Populations for whom use is Contraindicated

The medicine is strictly prohibited for patients with a known prolonged QT interval or congenital long QT syndrome. It is also contraindicated for individuals with known hypersensitivity to hydroxyzine, its active metabolites (cetirizine, levocetirizine), or any component of the formulation. Use in early pregnancy is contraindicated, and the medicine should not be given to nursing mothers.


Age and Organ Function Restrictions

Hydrozyxinum is approved for use in adults and certain pediatric populations (down to specific minimum ages for various forms). However, for older adults (geriatric), use is not recommended by some regulators or requires caution with initiation at the lowest dose due to decreased organ function and increased vulnerability to adverse effects.

Patients with impaired renal function or hepatic impairment require caution and potential modification due to reduced drug elimination. Caution is also necessary for patients with risk factors for QT prolongation, such as uncompensated heart failure or recent myocardial infarction. Caution is also advised for conditions exacerbated by anticholinergic activity, such as glaucoma or urinary retention.

What should I know about interactions with other medicines?

Interactions with other medicines and products

Official regulatory information for Hydroxyzinum establishes specific constraints regarding its concurrent use with other substances, primarily focused on additive effects and metabolic interference.


Contraindicated Combinations

Co-administration is strictly contraindicated with drugs that are known to prolong the QT interval and/or induce Torsade de Pointes. This includes, but is not limited to, certain Class IA and III antiarrhythmics, some antipsychotics, specific antibiotics, and other agents documented to increase the risk of serious cardiac rhythm disturbances.


Significant Interaction Categories

Interaction Type Interacting Agents Practical Implication
Potentiation (Pharmacodynamic) CNS Depressants (e.g., narcotics, barbiturates, alcohol) Consideration of increased central nervous system depression is required.
Metabolic Inhibition (Pharmacokinetic) Potent Inhibitors of CYP3A4/5 or Alcohol Dehydrogenase Increased blood concentrations of Hydroxyzinum may occur.
Additive Cardiac Risk (Pharmacodynamic) Bradycardia-inducing or Hypokalaemia/Hypomagnesaemia-inducing drugs Caution is required due to increased cardiac susceptibility.

Specific Regulatory Notes

  • The potentiating action of Hydroxyzinum on agents such as meperidine and barbiturates has been documented in official labeling.
  • Its action is not known to interfere with digitalis, and atropine and related alkaloids are not reported to be affected by co-administration.
  • Regulatory guidance advises that use in elderly patients is generally not recommended due to reduced drug elimination and increased vulnerability to adverse effects.

Mechanism of Action

Primary Action: Histamine mathbfH1 Receptor Blockade

Hydroxyzinum is primarily a competitive antagonist at the histamine mathbfH1 receptor. By binding reversibly to this receptor, it prevents the endogenous mediator histamine from binding and activating the receptor site. This interference with the H1 signaling cascade results in the targeted receptor pathway demonstrating reduced responsiveness to the local release of histamine.


Central Pathway Modulation

The drug is highly lipophilic, enabling its rapid distribution into central nervous system (CNS) pathways. Blockade of mathbfH1 receptors in the brain, particularly those regulating states of vigilance, modifies activating neural signals. This initiates signaling sequences that result in a pronounced CNS depressant effect. Hydroxyzinum also engages mechanisms that influence the serotonin mathbf5-mathbfHTmathbf2A pathway, further modulating CNS activity.


Ancillary Muscarinic Receptor Modulation

Hydroxyzinum additionally interacts with secondary targets, specifically muscarinic cholinergic receptors. This anticholinergic activity modulates key pathways associated with acetylcholine signaling, including those within smooth muscle tissue. Furthermore, M receptor-mediated signaling in the chemoreceptor trigger zone and nucleus of the solitary tract is altered.

Dosage and Administration Information

How to Use Hydroxyzinum: Official Administration Guidelines

The usage of Hydroxyzinum (Hydroxyzine) is defined by established parameters that outline the method, frequency, and quantity of administration. The medication is officially administered via the oral route (tablets, capsules, or solution) or by Intramuscular (IM) injection for acute or pre-procedural needs. All use is guided by the principle of utilizing the lowest effective dose for the shortest possible duration.

Official Dosing and Frequency

Standard dosing for adults typically ranges from 25 mg to 100 mg per dose, with daily regimens for conditions like anxiety and itching often divided and administered up to four times a day. For premedication or sedation, the medication is generally used as a single oral or IM dose.

Administration Requirements

Aspect Official Guideline
Timing in Relation to Meals Oral dosage forms can be taken with or without food.
Preparation The oral solution requires vigorous shaking before measuring a dose to ensure consistency.
Parenteral Route The injectable form is strictly for IM use and must not be administered intravenously or subcutaneously.

Population-Specific Dosing

Specific dosage adjustments are utilized for certain patient groups. Older adults are advised to use a lower dose, with a maximum recommended total daily dose of 50 mg. Furthermore, patients with renal or hepatic impairment may require a reduction in their total daily dosage, such as a 50% reduction for moderate to severe renal impairment. If a dose is missed, the standard approach is to skip the missed dose if it is almost time for the next scheduled dose, and not taking a double dose.

Recent Clinical Evidence

Research Evidence / Overview of Studies for Hydroxyzinum

Evidence for Use in Pruritus (Itching) and Allergic Skin Conditions

Research has examined the use of Hydroxyzinum in exploring how symptoms change over time related to itching (pruritus) due to conditions linked to inflammatory or irritative states, such as chronic hives (urticaria) and allergic skin issues. Short-term Randomized Controlled Trials (RCTs) were a key component of this research, comparing the treatment to a placebo or to other older antihistamines. Studies included adults relevant in trials assessing short-term or episodic symptom patterns of itching.

The research has explored how symptoms change over time by measuring standardized itch severity scores and assessing patient-reported outcomes describing perceived discomfort. Findings describe patterns observed in the studies where individuals reported changes in itch severity during the short-term study period. The evidence for this use is generally based on studies with short-term follow-up durations.


Evidence for Use in Short-Term Anxiety and Tension

Hydroxyzine was studied for conditions characterized by fluctuating or episodic manifestations of anxiety and tension. Research has primarily focused on research exploring short-term changes related to anxiety and tension. This evidence base includes short-term RCTs that compare the treatment to both placebo and other studied anxiolytics. These studies typically included adult outpatients.

The research explored outcomes related to systemic or functional imbalance by monitoring standardized anxiety rating scales and using clinician assessments. Findings indicate patterns where scores on anxiety scales were measured as changing in the observed populations during the short study interval. A point often noted in regulatory data is that systematic clinical studies have not been conducted to assess the drug's effect when used for longer than four months.


What is Still Uncertain about Hydroxyzinum Research

Key limitations include the modest sample sizes of many of the core studies and the limited information for long-term outcomes for its primary applications, such as the short-term study of anxiety symptoms. Comparative evidence is lacking in some areas, making it difficult to fully contextualize the observed patterns against newer, alternative treatments. Overall, the research provides context but not individual predictions, and the findings describe group patterns related to outcomes linked to inflammatory or irritative states and functional imbalance over defined, short time intervals.

Key Studies & References Hydroxyzine: MedlinePlus Drug Information (National Library of Medicine / NIH)

Frequently Asked Questions (FAQ)

Common questions about Hydroxyzinum (FAQ)

Q: How quickly does Hydroxyzinum usually start to have an effect?

A: According to official product information, Hydroxyzine is rapidly absorbed by the body. Sedative effects may begin relatively quickly, often starting within 15 to 45 minutes after taking the oral dose. The antihistaminic effects usually begin within about an hour.

Q: Is Hydroxyzinum classified as a controlled substance?

A: No, Hydroxyzine is not classified as a controlled substance under the U.S. Controlled Substances Act. Regulatory-aligned information notes that it is not classified as a controlled substance and is generally not associated with the same potential for abuse or dependency as those controlled medications.

Q: Is it possible for Hydroxyzinum to affect reaction time while driving or operating machinery?

A: Yes. Regulatory safety warnings advise caution regarding driving or operating heavy machinery. Patients are warned that these activities should be avoided until they are certain the medication does not impair their reaction time or cause excessive drowsiness.

Q: Is Hydroxyzinum the same drug as Vistaril or Atarax?

A: Hydroxyzine is the generic active ingredient found in these medicines. Atarax was a common brand name for hydroxyzine hydrochloride, and Vistaril was a common brand name for hydroxyzine pamoate. These different names refer to the same active medication substance.

Q: How long does the effect of Hydroxyzinum typically last?

A: The noticeable clinical effects typically last for a few hours. However, the body processes the medication over a longer period, with the reported half-life (the time it takes for half the drug to be eliminated) in adults generally ranging from approximately 14 to 25 hours.

Q: Does taking Hydroxyzinum affect the results of allergy skin tests?

A: Yes, as the medication is an antihistamine, it can interfere with or prevent a positive reaction to allergy skin tests. Official guidance notes that due to this interference, consultation with a healthcare professional regarding the appropriate timing for discontinuing the medication before testing is generally needed.

Q: Are there official statements regarding stopping Hydroxyzinum abruptly?

A: Official regulatory guidance advises that healthcare providers should periodically assess whether the medication is still useful for the patient. Stopping use or changing the regimen should only be done under the direction of a healthcare professional.

Q: Does Hydroxyzinum typically cause weight gain or loss?

A: Hydroxyzine is not commonly associated with direct or significant weight changes. However, post-marketing data has included reports of changes in appetite or reduced activity levels due to sedation, which may indirectly lead to some weight fluctuations.

Q: Is Hydroxyzinum a high-risk medication for overdose?

A: Regulatory safety information warns that taking more than the prescribed amount is dangerous. Symptoms of overdose can be severe and may include extreme drowsiness, confusion, rapid heart rate, seizures, and coma. If an overdose is suspected, emergency medical assistance should be sought immediately.

Q: Is there a link between Hydroxyzinum and restless legs syndrome?

A: Some clinical literature suggests a potential for it to worsen symptoms of Restless Legs Syndrome (RLS) in some individuals. This potential effect is not always listed as an official side effect but is considered in the context of the drug's activity.

Q: Do studies mention Hydroxyzinum being a non-addictive medication?

A: Regulatory-aligned documents note that Hydroxyzine is not associated with the same potential for abuse or dependency as certain other prescription medications.

Q: Is it true that Hydroxyzinum can sometimes increase appetite?

A: Yes, while not a primary or common side effect, changes in appetite, including the possibility of an increased appetite, have been reported in post-marketing safety data.

Q: Are there differences in how the body processes the tablet versus the liquid form of Hydroxyzinum?

A: Yes, regulatory data indicates that the liquid form may begin its sedative effect faster (sometimes within 5–10 minutes) compared to the tablets (30–45 minutes). However, the overall amount of the drug that the body absorbs and processes is generally very similar between the two oral forms.

Q: Is Hydroxyzinum available over the counter in some countries?

A: Official information from major regulatory bodies indicates that in countries like the United States, Canada, and the United Kingdom, Hydroxyzine is regulated as a prescription-only medication and is not available over the counter.

Q: Is Hydroxyzinum generally covered by insurance plans?

A: As a generic prescription medication, Hydroxyzine is typically covered by most major insurance plans, including commercial and government plans in the U.S. Context (like Medicare Part D). However, specifics regarding copays and coverage always vary by individual plan.

Q: Are there any common vision changes associated with Hydroxyzinum?

A: Yes. While not the most common side effect, regulatory-aligned patient materials list blurring of vision as a potential effect. This is related to the drug’s anticholinergic activity, which affects certain functions of the body.

Q: Is it common to experience dizziness when taking Hydroxyzinum?

A: Yes, official patient information often lists both dizziness and drowsiness among the common side effects of Hydroxyzine. These effects are related to the drug's activity in the central nervous system.

Q: Can Hydroxyzinum be taken alongside common antidepressants?

A: Caution is advised. The official label contraindicates the combination of Hydroxyzine with certain antidepressants that are known to prolong the QT interval (a measure of heart rhythm). Use alongside other antidepressants should always be assessed by a healthcare professional.

Q: Can Hydroxyzinum affect blood pressure?

A: The official product information primarily focuses on the cardiac risk of QT prolongation. Regulatory-aligned documents note that low blood pressure (hypotension) has been reported as a serious symptom in cases of overdose. Caution is advised for patients with existing heart conditions, as regulatory documents prioritize cardiac risk information.

Q: Is it possible to develop a tolerance to Hydroxyzinum over time?

A: Official research summaries note that systematic clinical studies have not been conducted to fully assess the drug’s effectiveness or effects when used for periods longer than four months. Therefore, information about tolerance with long-term use is limited.

Q: Can Hydroxyzinum be used as needed, or does it require regular daily use?

A: Regulatory-aligned patient materials confirm that Hydroxyzine can be taken either on a regular daily schedule or on an as-needed (PRN) basis. The specific pattern of use should be established with a healthcare professional.

Q: What is the chemical difference between Hydroxyzinum hydrochloride and pamoate?

A: Both Hydroxyzine hydrochloride and Hydroxyzine pamoate are different forms, or salts, of the active ingredient, Hydroxyzine. They differ in the acid counterion they are bonded to. This difference primarily affects their molecular weight and how they are formulated (e.g., hydrochloride is often the tablet form, pamoate is often the capsule or suspension form).

Q: What does official guidance suggest regarding taking Hydroxyzinum and grapefruit juice?

A: Official guidance warns against taking Hydroxyzine with strong inhibitors of the CYP3A4/5 enzyme, which is responsible for processing the drug. Grapefruit juice is widely recognized as a CYP3A4 inhibitor, suggesting a potential for the drug to accumulate in the bloodstream and increase the risk of side effects.

Q: Can Hydroxyzinum cause stomach upset or nausea?

A: While the drug can be used for its antiemetic (anti-nausea) properties, some patient information recommends taking it with food if stomach upset occurs. Additionally, nausea and vomiting are listed among the potential symptoms of overdose, highlighting a possible gastrointestinal effect.

Q: How does Hydroxyzinum differ from benzodiazepines in its mechanism?

A: Hydroxyzine is chemically distinct from the benzodiazepine class of drugs. Its mechanism of action relies primarily on blocking histamine receptors and suppressing activity in subcortical brain areas, rather than influencing the GABA neurotransmitter pathways that are targeted by benzodiazepines.

Q: Why is monitoring necessary for some patients taking Hydroxyzinum?

A: Monitoring may be necessary due to the risk of QT prolongation (requiring heart rhythm tests like ECGs) and the need for dosage adjustment in patients with kidney or liver impairment. These measures are taken to prevent the drug from accumulating in the body and increasing the risk of serious adverse effects.

Q: Does Hydroxyzinum interact with common herbal supplements?

A: Regulatory documents advise general caution when combining Hydroxyzine with any non-prescription product, including herbal supplements. Specific warnings are issued for any herbal products that might inhibit the CYP3A4/5 enzyme or cause central nervous system depression, as these can increase side effects.

How should Hydroxyzinum be stored and disposed of?

Storage and Disposal Requirements for Hydroxyzine

Official labeling mandates specific conditions to maintain the stability and safety of Hydroxyzine. The oral forms must be stored at Controlled Room Temperature, defined as 20^circ to 25 C (68^circ to 77 F), with permitted excursions up to 30 C. The injectable solution requires specific protection from light, and any unused portion of a single-dose vial must be discarded.

Packaging and Safety

All forms must be stored out of the reach of children; oral forms require dispensing in a tight container with a child-resistant closure. For disposal of unused or expired product, Hydroxyzine is not on the list of medicines to be flushed. Disposal should adhere to federal guidelines, utilizing a community drug take-back program or mixing the medication with an undesirable substance before sealing it for household trash.

Attention! Always consult to a doctor or pharmacist before using pills or medicines.

Available in countries:

Equivalent of Hydroxyzinum found in:

A-Z Index: