Hydroxyzine belongs to the class of medications called antihistamines. It is used to relieve itching and other symptoms caused by allergic conditions. It can help to alleviate itching due to an adverse reaction to opioid medications. It works by blocking the actions of one of the body's natural chemicals known as histamine. Histamine is responsible for many of the symptoms seen when an allergic reaction occurs. The calming effects of hydroxyzine result from its sedating side effect.

It is also used to manage anxiety and tension caused by situations such as dental procedures or acute emotional problems. Hydroxyzine is also used to control nausea and vomiting (except in pregnancy).

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

For adults and children weighing more than 40 kg, the recommended dose of hydroxyzine when taken by mouth is up to a maximum of 100 mg per day, divided into 3 or 4 doses.  For people over the age of 65 years, the maximum daily dose is 50 mg.

For children weighing less than 40 kg, the dose is based on body size, and is calculated as 2 mg per kilogram of body weight. This dose is then divided into 3 or 4 doses to be taken spaced out throughout the day. The maximum daily dose of hydroxyzine for this group is 80 mg per day.

Use an oral syringe to measure each dose of the liquid, as it gives a more accurate measurement than household teaspoons.

Hydroxyzine may be taken with or without food.

Many things can affect the dose of a medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Each 5 mL of mint-flavoured syrup contains 10 mg of hydroxyzine hydrochloride and 1.5 mg of sodium benzoate. Nonmedicinal ingredients: sucrose, water, alcohol, menthol, spearmint oil, peppermint oil, and sodium hydroxide or hydrochloric acid (for pH adjustment).

Do not take this medication if you:

• are allergic to hydroxyzine or any ingredients of the medication
• are in early pregnancy (first trimester)
• have had an allergic reaction to aminophylline or cetirizine
• have asthma and have had a breathing problem relating to histamine or allergies
• have a history of irregular heartbeat, other heart rhythm problems, or a family history of sudden cardiac death
• have untreated low levels of potassium or magnesium,
• have porphyria
• are taking certain medications that can affect heart rhythm, including:
• antidepressants (e.g., amitriptyline, citalopram, fluoxetine)
• 'azole' antifungals (e.g., itraconazole, ketoconazole, voriconazole)
• bronchodilators (e.g., formoterol, salmeterol)
• certain antibiotics (e.g., erythromycin, ciprofloxacin)
• medications for heart rhythm (e.g., flecainide, sotalol)
• medications to treat HIV/AIDS (e.g., atazanavir, ritonavir, saquinavir)
• domperidone
• ondansetron

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent. The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• drowsiness
• dry mouth, nose, or throat
• flushing
• headache
• itching

Although most of these side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• hallucinations (seeing or hearing things that aren't there)
• skin rash
• symptoms of irregular heartbeat (e.g., chest pain, dizziness, rapid, pounding heartbeat, shortness of breath)
• symptoms of too much medication (e.g., nausea, vomiting, slurred speech, excitement, restlessness, nervousness, irritability, or tremors)

Stop taking the medication and seek immediate medical attention if any of the following occur:

• seizures
• signs of an allergic reaction (e.g., rash, itching, or hives)
• signs of a severe skin reaction such as blistering, peeling, a rash covering a large area of the body, a rash that spreads quickly, or a rash combined with fever or discomfort

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Abnormal heart rhythms: This medication can cause abnormal heart rhythms. Certain medications (e.g., sotalol, quinidine, thioridazine, chlorpromazine, pimozide, moxifloxacin, mefloquine, pentamidine, arsenic trioxide, tacrolimus) can increase the risk of a type of abnormal heart rhythm called QT prolongation and should not be used in combination with hydroxyzine. You are more at risk for this type of abnormal heart rhythm and its complications if you:

• are female
• are older than 65 years of age
• have a family history of sudden cardiac death
• have a history of heart disease or abnormal heart rhythms
• have a slow heart rate
• have congenital prolongation of the QT interval
• have diabetes
• have had a stroke
• have low potassium, magnesium, or calcium levels
• have nutritional deficiencies

If you have heart disease and abnormal heart rhythms, or people are taking certain medications , discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Alcohol and other medications that cause drowsiness: People taking this medication should not combine it with alcohol and avoid combining it with other medications, such as narcotic pain relievers or sedatives, that cause drowsiness. Doing so can cause additive drowsiness and reduced breathing, as well as other side effects, which can be dangerous.

Breathing problems: People with breathing problems such as asthma, emphysema, or chronic bronchitis may find that hydroxyzine makes breathing more difficult. It can dry the mucus in the lungs, making it more difficult to clear the lungs. If you experience difficulty breathing, stop taking the medication and contact your doctor.

Digestive system problems: Antihistamines, such as hydroxyzine, cause the passage of food though the digestive system to slow down. If you have any condition that already slows down the movement of food through the stomach and intestines, hydroxyzine may make this worse.

Drowsiness/reduced alertness: Hydroxyzine may cause drowsiness or dizziness, affecting your ability to drive or operate machinery. Avoid driving, operating machinery, or performing other potentially hazardous tasks until you have determined how you are affected by this medication.

Enlarged prostate and urinary difficulties: Hydroxyzine may worsen urinary difficulties. If you have an enlarged prostate or difficulty starting urination, including a blockage from the bladder, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Epilepsy: Hydroxyzine should be used with caution by people with epilepsy, as it may increase the risk for seizures. If you have a history of seizures, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Glaucoma: This medication may cause a slight increase in pressure in the eye and therefore should be used with caution by anyone with glaucoma. If you have glaucoma, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

If you notice vision changes while you are taking this medication, contact your doctor.

Kidney function: The kidneys are partially responsible for removing this medication from your body. Kidney disease or reduced kidney function may cause this medication to build up in the body, causing side effects. If you have reduced kidney function or kidney disease, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Liver function: Liver disease or reduced liver function may cause this medication to build up in the body, causing side effects. If you have liver problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Myasthenia gravis: Hydroxyzine may worsen the muscle weakness experienced by people with myasthenia gravis. This medication should be used with caution if you have myasthenia gravis.

Sedation: The sedating effect of hydroxyzine must be considered when the medication is used at the same time as other sedating medications such as narcotics, non-narcotic pain relievers, sleeping pills, sedatives, barbiturates, or alcohol.

Skin reactions: Rarely, people taking hydroxyzine experience a severe skin reaction that can be life-threatening. These reactions may start as a puffy, red skin rash that forms many small blisters, covering a large area of the body. If you experience these symptoms or worsening of an existing skin condition, contact your doctor immediately.

Thyroid disease: Hydroxyzine may cause symptoms of an overactive thyroid gland (hyperthyroidism). If you have thyroid problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Pregnancy: Hydroxyzine should not be used during early pregnancy. It may be used during later pregnancy only if the potential benefits outweigh the risks.

Breast-feeding: It is not known if hydroxyzine passes into breast milk. If you are a breast-feeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Seniors: Seniors may be at increased risk for the sedating and impaired coordination effects of this medication. Seniors should use extra caution, for example, when getting up during the night.

There may be an interaction between hydroxyzine and any of the following:

• aclidinium
• alcohol
• amantadine
• amphetamines (e.g., dextroamphetamine, lisdexamfetamine)
• other antihistamines (e.g., azelastine, bilastine, cetirizine, doxylamine, diphenhydramine, loratadine, rupatadine)
• antiarrhythmic medications (e.g., amiodarone, flecainide, procainamide, quinidine, sotalol)
• anti-psychotics (e.g., chlorpromazine, clozapine, haloperidol, olanzapine, quetiapine, risperidone)
• atropine
• barbiturates (e.g., butalbital, pentobarbital phenobarbital)
• belladonna
• benzodiazepines (e.g., alprazolam, diazepam, lorazepam)
• benztropine
• betahistine
• botulinum toxin
• brimonidine
• buprenorphine
• cannabis
• chloral hydrate
• clidinium
• clonidine
• darifenacin
• dimenhydrinate
• diphenoxylate
• diuretics (water pills; e.g., amiloride, furosemide, hydrochlorothiazide)
• domperidone
• donepezil
• efavirenz
• eluxadoline
• entacapone
• esketamine
• fesoterodine
• galantamine
• glucagon
• glycopyrrolate
• grapefruit juice
• HIV protease inhibitors (e.g., atazanavir, ritonavir, saquinavir)
• ipratropium
• kava kava
• laxatives
• lemborexant
• long-acting beta 2 agonists (e.g., formoterol, salmeterol)
• macrolide antibiotics (e.g., clarithromycin, erythromycin)
• methadone
• methotrimeprazine
• metoclopramide
• metyrosine
• mifepristone
• mirabegron
• mirtazapine
• moclobemide
• muscle relaxants (e.g., baclofen, cyclobenzaprine, methocarbamol, orphenadrine)
• nabilone
• narcotic pain relievers (e.g., codeine, fentanyl, morphine, oxycodone, tapentadol, tramadol)
• nitroglycerin
• oxybutynin
• potassium chloride
• pramipexole
• pregabalin
• protein kinase inhibitors (e.g., lapatinib, pazopanib, sunitinib, vandetanib)
• quinine
• quinolone antibiotics (e.g., ciprofloxacin, ofloxacin, )
• rivastigmine
• ropinirole
• rotigotine
• scopolamine
• seizure medications (e.g., carbamazepine, clobazam, levetiracetam, phenobarbital, phenytoin, primidone, rufinamide, topiramate, valproic acid, zonisamide)
• selective serotonin reuptake inhibitors (SSRIs; e.g., citalopram, fluoxetine, paroxetine, sertraline)
• serotonin antagonists (anti-emetic medications; e.g., granisetron, ondansetron,)
• solifenacin
• stiripentol
• tacrolimus
• tetrabenazine
• thiazide diuretics (water pills; e.g., hydrochlorothiazide, indapamide, metolazone)
• tiotropium
• tizanidine
• tolterodine
• tranylcypromine
• trazodone
• tricyclic antidepressants (e.g., amitriptyline, clomipramine, desipramine, trimipramine)
• trospium
• umeclidinium
• valerian
• venlafaxine
• zolpidem
• zopiclone

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.