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Updated on December 14, 2021

Hydroxyzine Overdose

What is Hydroxyzine (& What Does it Treat)?

Hydroxyzine Pamoate is in a class of medicines called antihistamines. It's a first-generation antihistamine. It has weak sedative, anticholinergic, and antiemetic properties.

It leads to sedation and breathing difficulties by inhibiting the hypothalamic H-1 histamine receptors involved in the sleep-wake cycle.

The drug sells under the brand names Atarax and Vistaril

Cetirizine is an over-the-counter antihistamine used to treat allergic rhinitis, dermatitis, and urticaria. It's non-sedating for most people. Cetirizine is a second-generation antihistamine.

Hydroxyzine blocks the action of histamine. This is a substance in the body that leads to allergic symptoms. It also decreases activity in the central nervous system (CNS).

Adults and children take Hydroxyzine Pamoate to relieve itching resulting from allergic reactions on the skin, such as hives. It is also used alone or in combination with other medicines to treat medical conditions like anxiety and tension in adults and children.


The medication is also used with other medicines for sedation before and after general anesthesia for surgery. It depresses the central nervous system (CNS).

The drug is available in the following forms:

  • Capsules
  • Tablets
  • Syrup
  • A suspension (to take by mouth)

Usually, Hydroxyzine is taken three or four times a day. Follow the directions on the prescription label correctly. Ask your doctor or a healthcare professional to explain any parts of the treatment you do not understand.

Do not consume more or less Hydroxyzine or take it more often than prescribed by your doctor. If you take Hydroxyzine by suspension, shake it well before use to mix the solution evenly.

Antihistamines like Hydroxyzine are safe when taken correctly.

Here are some tips and advice to avoid consuming too much of the drug:

  • Do not double up on doses
  • Keep the drugs out of reach of children
  • Do not take two doses too close together
  • Ensure you read labels carefully

Side Effects & Risks of Hydroxyzine Use

Taking Hydroxyzine may result in side effects and risks.

There are precautions for its use in:

  • Pregnant women
  • Those who have recently had a heart attack
  • Those with slow or irregular heartbeats
  • Those with glaucoma
  • Those with low or high potassium levels

Speak with your doctor or a healthcare professional if any of the following symptoms are severe or persist after ingestion:

  • Dry mouth
  • Constipation (especially in older adults)
  • Confusion (especially in older adults)
  • Dizziness
  • Headache
  • Hypotension
  • Hypersensitivity 

Some side effects can be more serious.

If you experience any of these symptoms or side effects, speak with your doctor or a healthcare professional immediately:

  • Unintentional trembling or shaking movements
  • Seizures 

If you experience any of the following side effects or symptoms of a severe skin condition, stop taking Hydroxyzine and speak with your doctor or healthcare professional immediately:

  • Pus-filled rash, blister-like sores or lesions
  • Areas of redness or swelling on the skin
  • Fever

Hydroxyzine may lead to other side effects. Speak with your doctor if you notice any abnormalities while taking this medicine. If you have glaucoma, you should also speak with your doctor before taking the drug. 

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Can You Overdose on Hydroxyzine?

Yes, it is possible to overdose on Hydroxyzine. Hydroxyzine overdose occurs when an individual takes more than the usual or recommended amount of the medication. This can be done by accident or intentionally.

Allergy medications like Hydroxyzine are considered safe when used correctly and can deliver quick relief from symptoms. However, an antihistamine overdose can be life-threatening, so it is essential to understand proper dosing to avoid toxicity.

This drug shouldn't be used for more than 4 months. Contact your doctor if your symptoms don't improve in this timeframe.

Drugs to Avoid While Taking Hydroxyzine

Hydroxyzine can interact with other drugs you take. If you do not know whether it is safe to take Hydroxyzine with another medicine, speak with your doctor or a pharmacist. 

Drug interactions may alter how your medications work or increase your risk for severe side effects. A good idea is to keep a list of all the products you use and share it with your doctor or pharmacist. This includes prescription and non-prescription drugs and herbal supplements.

Do not begin, stop, or alter the dosage of any medicines without a healthcare professional’s approval. 

The following drugs may cause drowsiness, and you should tell your doctor or pharmacist if you are planning on taking them with Hydroxyzine:

  • Opioid pain or cough relievers, such as codeine or hydrocodone
  • Alcohol
  • Marijuana (cannabis)
  • Medicines for sleep or anxiety, like alprazolam, lorazepam, or zolpidem
  • Muscle relaxants, like carisoprodol or cyclobenzaprine
  • Other antihistamines, like diphenhydramine or promethazine
  • Drugs known to prolong QT interval
  • Class III antiarrhythmics
  • Some antimalarials (e.g., mefloquine)
  • Some antibiotics (e.g., erythromycin, levofloxacin)
  • Gastrointestinal agents (e.g., prucalopride)
  • Anti-cancer drugs (e.g. toremifene, vandetanib)

Always check the disclaimer labels on your medications, especially allergy or cough-and-cold products. This is because they may contain ingredients that lead to drowsiness. 

Do not use Hydroxyzine with any other antihistamines applied to the skin, like diphenhydramine cream, ointment, or spray. This is because increased side effects could occur.

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Symptoms of Hydroxyzine Overdose

Dilated pupils are the most common symptom of a Hydroxyzine overdose.

Below is the full list of  the vital signs of a Hydroxyzine overdose:

  • Dilated pupils
  • Shortness of breath
  • Difficulty urinating
  • Blurred vision
  • Dry mouth
  • Enlarged pupils
  • Dry eyes
  • Ringing in the ears
  • Rapid heartbeat
  • Low blood pressure
  • Pounding heartbeat (palpitations)
  • Agitation
  • Coma
  • Lack of responsiveness
  • Decreased level of consciousness
  • Seizures
  • Delirium
  • Depression
  • Disorientation 
  • Dizziness
  • Sleepiness
  • Excitation
  • Hallucinations
  • Nervousness
  • Tremor
  • Uncoordinated movement
  • Unsteadiness
  • Dry, red, or flushed skin
  • Nausea
  • Vomiting

How Long Do Overdose Symptoms Last?

It is challenging to predict when an overdose may occur or how long it will last. The length of overdose symptoms depends on various factors, such as how much Hydroxyzine was taken and the body weight and size of the individual.

If you are concerned about a potential overdose, it is essential to seek medical attention immediately. Symptoms do not go away on their own. Without proper medical help, overdoses are almost always fatal. 

How Dangerous Are They? 

Recovery from a Hydroxyzine overdose is likely if the person survives the first 24 hours.

However, the following complications may lead to permanent disability:

  • Pneumonia
  • Muscle damage from lying on a hard surface for an extended period
  • Brain damage from a lack of oxygen

Few people die from an antihistamine overdose unless they have severe heart rhythm disturbances or breathing issues. However, there have been some deaths due to antihistamine toxicity. These include both accidental and intentional overdoses.

Deaths typically occur when a Hydroxyzine overdose leads to severe complications, including:

  • Respiratory distress
  • Cardiac arrest
  • Seizures

Each individual’s tolerance to antihistamines varies. However, toxicity typically occurs when a person consumes three to five times the recommended dosage.

When to Visit the ER

Some side effects and symptoms of taking antihistamines can mimic overdosage of the drug.

These side effects include:

  • Mild nausea
  • Dizziness
  • Vomiting
  • Diarrhea
  • Stomach pain

These side effects do not usually require medical attention. They may subside as your body adjusts to the medicine. 

However, it is always best to check with a doctor if you have side effects. You may need to adjust your dosage or take a different medicine.

The difference between side effects and an overdose is usually the severity of symptoms.

If someone is experiencing the following symptoms, they must visit the emergency room:

  • Rapid heart rate
  • Tightness in the chest
  • Convulsions

Before calling for emergency help, have the following information ready:

  • The individual’s age, weight, and condition
  • Name of the medication, including ingredients and strength if known
  • Time the medicine was swallowed
  • Amount of medicine swallowed
  • Whether the medicine was prescribed for the individual

Treatment for Antihistamine Overdoses

Antihistamine overdose treatment works to stabilize the individual’s health and provides supportive care. The patient will likely receive activated charcoal in the hospital. This product is typically used in emergencies to help reverse the effects of drug poisoning.

Activated charcoal works as an antidote, stopping the absorption of toxins and chemicals from entering the body from the stomach. Toxins then bind to the charcoal and leave the body through bowel movements.

Additionally, treatment may include cardiac and respiratory monitoring. The prognosis depends on the quantities of antihistamine consumed and the extent of an overdose. However, a full recovery is possible with immediate treatment.

If possible, bring the antihistamine product to the hospital with you. 

Tests that may be performed during an antihistamine overdose include:

  • Blood and urine tests 
  • Chest x-ray ECG (electrocardiogram or heart tracing)

Treatments may include: 

  • Fluids through a vein (by IV) 
  • Medications to treat symptoms 
  • Activated charcoal
  • Laxatives
  • Breathing assistance, including a tube through the mouth into the lungs and connected to a ventilator
  • Activated charcoal if the patient was brought in within the first hour of hydroxyzine overdose
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  1. Hydroxyzine, MedlinePlus, January 2021, 
  2. Hydroxyzine overdose, MedlinePlus, February 2021, 
  3. Borowy CS, Mukherji P. Antihistamine Toxicity. [Updated 2020 Nov 19]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan, 
  4. FDA warns about serious problems with high doses of the allergy medicine diphenhydramine (Benadryl), United States Food and Drug Administration, September 2020, 
  5. Randall, Katrina L, and Carolyn A Hawkins. “Antihistamines and allergy.” Australian prescriber vol. 41,2 : 41-45, 
  6. Church, Martin K, and Diana S Church. “Pharmacology of antihistamines.” Indian journal of dermatology vol. 58,3 : 219-24,

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