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Medical Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice.
Other
Hydroxyzine Dihydrochloride is a first-generation antihistamine with potent anxiolytic, sedative, and antipruritic properties, used to treat anxiety and allergic skin reactions.
Name
Hydroxyzine Dihydrochloride
Raw Name
HYDROXYZINE DIHYDROCHLORIDE
Category
Other
Drug Count
5
Variant Count
183
Last Verified
February 17, 2026
RxCUI
995258, 995281, 995218, 995241, 1794554, 1794552, 995270, 995285
UNII
76755771U3
About Hydroxyzine Dihydrochloride
Hydroxyzine Dihydrochloride is a first-generation antihistamine with potent anxiolytic, sedative, and antipruritic properties, used to treat anxiety and allergic skin reactions.
Detailed information about Hydroxyzine Dihydrochloride
This page is for informational purposes only and does not replace medical advice. Consult a qualified healthcare professional before using any medication containing Hydroxyzine Dihydrochloride.
First synthesized in the 1950s and approved by the U.S. Food and Drug Administration (FDA) in 1956, Hydroxyzine Dihydrochloride has remained a staple in clinical practice for seven decades. It is chemically designated as 2-[2-[4-[(4-chlorophenyl)-phenylmethyl]piperazin-1-yl]ethoxy]ethanol dihydrochloride. While it is primarily classified as an H1-receptor antagonist, its unique pharmacological profile distinguishes it from other antihistamines. Healthcare providers typically prescribe it for the symptomatic relief of anxiety and tension associated with psychoneurosis, as well as for the management of pruritus (severe itching) caused by allergic conditions such as chronic urticaria (hives) and atopic or contact dermatoses.
At the molecular level, Hydroxyzine Dihydrochloride acts as a competitive antagonist at the H1 histamine receptors located throughout the body and the brain. In the periphery (the body outside the brain), blocking these receptors prevents histamine from binding to blood vessels and nerves, which reduces the redness, swelling, and itching associated with allergic reactions. However, its most profound effects occur within the subcortical region of the central nervous system.
In addition to its antihistaminic properties, Hydroxyzine Dihydrochloride exhibits moderate antagonistic activity at the 5-HT2A (serotonin) receptors and D2 (dopamine) receptors, though to a much lesser extent than its H1 activity. The blockade of serotonin receptors in the brain is believed to contribute significantly to its anxiolytic effects. Unlike benzodiazepines (such as Xanax or Valium), Hydroxyzine Dihydrochloride does not affect the Gamma-Aminobutyric Acid (GABA) system, which means it does not carry the same risk for physical dependence, addiction, or withdrawal symptoms. This makes it a preferred option for patients with a history of substance abuse or those requiring long-term management of mild-to-moderate anxiety.
Furthermore, Hydroxyzine Dihydrochloride possesses anticholinergic properties (blocking the neurotransmitter acetylcholine). This leads to its sedative effects but also accounts for several of its common side effects, such as dry mouth and blurred vision. The drug suppresses activity in certain key regions of the subcortical area of the brain, including the hypothalamus and brainstem, which helps to calm the nervous system without impairing mental alertness as severely as some other sedatives.
Understanding the pharmacokinetics (how the body processes the drug) of Hydroxyzine Dihydrochloride is essential for optimizing its therapeutic benefits while minimizing risks.
Hydroxyzine Dihydrochloride is FDA-approved for several distinct clinical indications:
Hydroxyzine Dihydrochloride is available in several formulations to accommodate different patient needs and clinical settings:
> Important: Only your healthcare provider can determine if Hydroxyzine Dihydrochloride is right for your specific condition. The choice of formulation and dosage will depend on your medical history, age, and the severity of your symptoms.
The dosage of Hydroxyzine Dihydrochloride is highly individualized and depends on the condition being treated and the patient's response to the medication. According to clinical guidelines and FDA-approved labeling, the standard adult dosages are as follows:
Hydroxyzine Dihydrochloride is approved for use in children, but the dosage must be carefully calculated based on the child's weight and age to ensure safety.
Because the metabolites of Hydroxyzine Dihydrochloride, including cetirizine, are primarily excreted through the kidneys, patients with impaired renal function (kidney disease) may require a reduced dosage. A common clinical practice is to reduce the starting dose by 50% in patients with moderate to severe renal impairment to prevent the accumulation of the drug in the system, which could lead to excessive sedation.
Hydroxyzine Dihydrochloride is extensively metabolized by the liver. In patients with hepatic cirrhosis or other forms of liver dysfunction, the half-life of the drug can be significantly increased. Healthcare providers typically recommend a lower daily dose or increasing the interval between doses for these patients to avoid toxicity.
The American Geriatrics Society (Beers Criteria) advises caution when using Hydroxyzine Dihydrochloride in the elderly. Due to age-related declines in kidney and liver function, as well as an increased sensitivity to anticholinergic effects (such as confusion and dry mouth), the starting dose for older adults should be at the low end of the range (e.g., 10 mg to 25 mg). Many experts recommend avoiding this medication in the elderly if safer alternatives are available.
To ensure the safety and efficacy of Hydroxyzine Dihydrochloride, patients should follow these specific instructions:
If you miss a dose of Hydroxyzine Dihydrochloride, take it as soon as you remember. However, if it is almost time for your next scheduled dose, skip the missed dose and resume your regular dosing schedule. Do not take two doses at once to make up for a missed one, as this increases the risk of excessive sedation and side effects.
An overdose of Hydroxyzine Dihydrochloride can be serious and requires immediate medical attention. Signs of overdose may include:
In the event of a suspected overdose, contact your local poison control center or seek emergency medical care immediately. Treatment usually involves supportive care, as there is no specific antidote for hydroxyzine poisoning.
> Important: Follow your healthcare provider's dosing instructions. Do not adjust your dose without medical guidance.
Like all medications that affect the central nervous system, Hydroxyzine Dihydrochloride is associated with several common side effects. Most of these are related to its antihistaminic and anticholinergic properties and are usually dose-dependent (meaning they become more pronounced at higher doses).
These side effects may occur in a significant minority of patients and should be monitored:
While rare, these side effects are clinically significant and may require a change in medication:
> Warning: Stop taking Hydroxyzine Dihydrochloride and call your doctor immediately if you experience any of these serious symptoms.
Hydroxyzine Dihydrochloride is generally intended for short-term or intermittent use. Long-term use (months to years) has not been extensively studied in clinical trials. Potential concerns with prolonged use include:
At this time, the FDA has not issued a "Black Box Warning" for Hydroxyzine Dihydrochloride. However, regulatory agencies in Europe (such as the EMA) have issued strong warnings regarding the risk of heart rhythm disturbances, recommending that the daily dose not exceed 100 mg in adults and 55 mg in the elderly.
Report any unusual symptoms to your healthcare provider immediately. Your doctor may perform an electrocardiogram (ECG) to monitor your heart rhythm if you are at risk for cardiovascular complications.
Hydroxyzine Dihydrochloride is a potent medication that requires careful medical supervision. The most critical safety consideration is its effect on the central nervous system. Because it causes significant drowsiness, patients must be extremely cautious when performing tasks that require mental alertness. Furthermore, its potential to affect the heart's electrical activity necessitates a thorough cardiovascular screening before initiation.
No FDA black box warnings for Hydroxyzine Dihydrochloride. However, it is important to note that the lack of a black box warning does not imply the drug is without serious risks, particularly regarding cardiac safety and CNS depression.
Hydroxyzine Dihydrochloride has been associated with a prolongation of the QT interval on an electrocardiogram (ECG). This is a measure of the time it takes for the heart's ventricles to electrically relax. If the QT interval becomes too long, it can trigger a life-threatening heart rhythm called Torsades de Pointes.
The sedative effects of Hydroxyzine Dihydrochloride are additive. This means that if you combine it with other substances that slow down the brain—such as alcohol, benzodiazepines, opioids, or sleep aids—the effect can be dangerous or even fatal. Severe CNS depression can lead to respiratory depression (dangerously slow breathing), coma, and death.
Patients should be warned about the possibility of severe skin reactions. If a rash develops, especially one accompanied by fever or small blisters, the medication must be discontinued immediately, and medical help must be sought. Re-exposure to hydroxyzine after an AGEP event is strictly contraindicated.
Due to its anticholinergic properties, hydroxyzine should be used with caution in patients with:
While routine blood work is not always required for healthy adults on short-term hydroxyzine, certain patients may need monitoring:
Hydroxyzine Dihydrochloride significantly impairs the mental and physical abilities required for driving a car or operating heavy machinery. Patients should not engage in these activities until they are certain how the medication affects them. Even if you do not "feel" sleepy, your reaction times and coordination may be compromised.
Alcohol must be strictly avoided while taking Hydroxyzine Dihydrochloride. Alcohol increases the sedative effects of the drug, leading to extreme drowsiness, impaired judgment, and an increased risk of respiratory depression.
Unlike benzodiazepines, Hydroxyzine Dihydrochloride does not typically require a slow tapering process to prevent withdrawal. However, if you have been taking it for a long period, you should consult your doctor before stopping. Abruptly stopping the medication may cause a return of the original symptoms (rebound anxiety or itching).
> Important: Discuss all your medical conditions with your healthcare provider before starting Hydroxyzine Dihydrochloride.
Certain medications should never be taken with Hydroxyzine Dihydrochloride due to the extreme risk of life-threatening heart rhythm disturbances (QT prolongation).
Clinical Consequence: These combinations significantly increase the risk of Torsades de Pointes, which can lead to sudden cardiac arrest.
Hydroxyzine Dihydrochloride can interfere with the results of allergy skin tests. Because the drug blocks the H1 receptors, it will prevent the "wheal and flare" reaction that doctors look for during skin testing.
Management: Patients should typically stop taking Hydroxyzine Dihydrochloride at least 72 to 96 hours before undergoing allergy skin testing to ensure accurate results.
> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking. A complete list helps your pharmacist check for dangerous interactions.
There are several situations where Hydroxyzine Dihydrochloride must never be used because the risks far outweigh any potential benefits.
These conditions require a careful risk-benefit analysis by a healthcare professional:
Patients who are allergic to piperazine derivatives (a class of chemical compounds) may also be allergic to Hydroxyzine Dihydrochloride. This includes medications like cyclizine or meclizine. Additionally, because hydroxyzine is metabolized into cetirizine (Zyrtec), an allergy to cetirizine is a strong predictor of an allergy to hydroxyzine.
> Important: Your healthcare provider will evaluate your complete medical history before prescribing Hydroxyzine Dihydrochloride. Always be honest about your past allergic reactions and heart health.
Hydroxyzine Dihydrochloride is classified by the FDA as Pregnancy Category C (though this system is being phased out, it remains a common reference).
It is not known with certainty how much Hydroxyzine Dihydrochloride passes into human breast milk. However, because it is a low-molecular-weight drug, some transfer is likely.
Hydroxyzine Dihydrochloride is approved for use in children as young as infants for sedation and pruritus.
The elderly represent a high-risk population for Hydroxyzine Dihydrochloride.
In patients with a Glomerular Filtration Rate (GFR) below 50 mL/min, the excretion of the active metabolite cetirizine is impaired.
For patients with liver cirrhosis (Child-Pugh Class A or B), the clearance of hydroxyzine is reduced by approximately 30-40%.
> Important: Special populations require individualized medical assessment to ensure that the dosage is safe and effective for their unique physiological needs.
Hydroxyzine Dihydrochloride is a competitive H1-receptor antagonist. It works by binding to the H1 receptors on the surface of cells, preventing histamine from triggering the allergic and inflammatory responses. Its anxiolytic effect is distinct from its antihistamine effect; it is thought to result from its activity in the subcortical regions of the brain (the limbic system and reticular formation). By modulating serotonin (5-HT2A) and dopamine (D2) receptors in these areas, it reduces the emotional response to stress without causing the significant motor impairment associated with higher-potency tranquilizers.
| Parameter | Value |
|---|---|
| Bioavailability | Approximately 70-80% |
| Protein Binding | 93% (primarily Albumin) |
| Half-life | 20-25 hours (Adults); 30+ hours (Elderly) |
| Tmax | 2.1 hours |
| Metabolism | Hepatic (Alcohol Dehydrogenase & CYP3A4/2D6) |
| Excretion | Renal (70% as metabolites); Fecal (minor) |
Hydroxyzine Dihydrochloride is a first-generation antihistamine in the piperazine subclass. Related medications include meclizine (used for vertigo) and cetirizine (the second-generation metabolite used for allergies). It is therapeutically categorized as an antipruritic, anxiolytic, and sedative-hypnotic.
Medications containing this ingredient
Common questions about Hydroxyzine Dihydrochloride
Hydroxyzine Dihydrochloride is primarily used for the symptomatic relief of anxiety and tension associated with psychoneurosis. It is also highly effective in treating pruritus (severe itching) caused by allergic conditions like hives or eczema. Additionally, healthcare providers may use it as a sedative before or after surgery to help patients relax. Because it is not a benzodiazepine, it is sometimes preferred for anxiety in patients where addiction is a concern. Always use it exactly as your doctor prescribes for your specific condition.
The most common side effect is significant drowsiness or sleepiness, which often improves after a few days of use. Many patients also experience dry mouth (xerostomia) due to the drug's anticholinergic properties. Other frequent side effects include fatigue, dizziness, and occasionally blurred vision. Because it can cause such strong sedation, you should not drive or operate machinery until you know how it affects you. If these effects persist or become bothersome, consult your healthcare provider.
No, you should strictly avoid alcohol while taking Hydroxyzine Dihydrochloride. Both substances are central nervous system depressants, meaning they slow down brain activity. When taken together, they can cause extreme drowsiness, dangerous levels of respiratory depression, and severely impaired motor skills. This combination significantly increases the risk of accidents, falls, and even fatal overdose. Always inform your doctor about your alcohol consumption habits before starting this medication.
Hydroxyzine Dihydrochloride is generally considered unsafe during the first trimester of pregnancy and is contraindicated during this period. There is evidence from animal studies suggesting it may cause fetal harm or birth defects when used early in development. During the second and third trimesters, it should only be used if the potential benefits clearly outweigh the risks to the fetus. If you are pregnant or planning to become pregnant, discuss safer alternatives for anxiety or allergies with your doctor. Most clinicians prefer to avoid its use throughout pregnancy if possible.
For the relief of itching and allergic symptoms, Hydroxyzine Dihydrochloride typically begins working within 15 to 30 minutes. If you are taking it for anxiety or as a sedative, you can expect to feel the calming effects within 30 to 60 minutes after oral administration. The peak effect usually occurs around 2 hours after the dose is taken. The sedative effects generally last for 4 to 6 hours, though you may feel slightly groggy for longer. The anti-itch benefits can often be felt for up to 24 hours due to its active metabolite.
Yes, Hydroxyzine Dihydrochloride can generally be stopped suddenly without the risk of physical withdrawal symptoms, as it is not a habit-forming medication like benzodiazepines. However, you should only stop the medication after consulting with your doctor. If you stop it abruptly, the symptoms it was treating—such as severe itching or anxiety—may return quickly. Your doctor may suggest a gradual reduction if you have been taking high doses for a long period to see if your symptoms remain under control. Always follow professional medical advice regarding discontinuation.
If you miss a dose, take it as soon as you remember. If it is almost time for your next scheduled dose, skip the missed dose and continue with your regular timing. Never take two doses at once to "catch up," as this can lead to excessive sedation and increase the risk of serious side effects like heart rhythm issues. If you frequently miss doses, consider setting an alarm or using a pill organizer. Consistency is key to maintaining the therapeutic levels needed to control your symptoms.
Weight gain is not a commonly reported side effect of Hydroxyzine Dihydrochloride in short-term clinical trials. However, because the medication causes significant drowsiness and fatigue, some patients may become less active, which could lead to weight gain over time. Additionally, antihistamines as a class have been occasionally linked to increased appetite in some individuals. If you notice significant changes in your weight while taking this medication, discuss it with your doctor to determine the cause. Maintaining a balanced diet and regular activity can help mitigate this risk.
Hydroxyzine Dihydrochloride has many potential drug interactions, some of which are very serious. It should not be taken with medications that affect heart rhythm (like certain antibiotics or antiarrhythmics) or other drugs that cause sedation (like opioids or sleep aids). It can also interact with anticholinergic drugs, increasing the risk of dry mouth, constipation, and confusion. Always provide your doctor and pharmacist with a complete list of all prescription and over-the-counter medications you are taking. They will check for interactions to ensure your treatment plan is safe.
Yes, Hydroxyzine Dihydrochloride is widely available as a generic medication, which is typically much more affordable than brand-name versions. The brand name Atarax has been discontinued in many markets, but the generic equivalent is identical in terms of active ingredient, strength, and efficacy. Generic versions must meet the same strict FDA standards for quality and safety as the original brand-name drug. You can find it in various forms, including tablets and oral solutions, at most retail pharmacies. Check with your insurance provider to see how it is covered under your plan.