How many times a day can you take cetirizine

Cetirizine is an antihistamine used to treat and prevent allergies such as hay fever. Find out how to take it safely and possible side effects.

• Belongs to a group of medicines known as antihistamines (allergy treatment)
• Non-sedating antihistamine

• Zista®
• Histaclear®
• Allerid C®
• Cetirizine-AFT® 
• Zyrtec®
• Razene®
• Zetop®

What is cetirizine?

Cetirizine is used to treat and prevent allergies such as hay fever (sneezing, runny or itchy nose, itchy eyes) or skin allergies such as hives (itching, redness, lumps). It works by blocking a chemical in your body, called histamine, which is released during an allergic reaction. 

Cetirizine belongs to a group of medicines known as antihistamines. Cetirizine is a non-sedating antihistamine, which means that it is less likely to cause drowsiness or make you feel sleepy. In New Zealand, cetirizine is available as tablets or as a liquid. Read more about antihistamines.

Dose

• The usual dose of cetirizine for adults and children over 12 years, is 1 tablet (10 milligrams) once a day.
• The dose for children under 12 years will depend on their age and weight. Your doctor or pharmacist will advise you on the correct dose for your child.
• You can just take cetirizine on the days you need it. It can be restarted if the symptoms come back. 
• Some people take cetirizine for a few weeks when their allergies are a problem, such as in springtime. Others take it long-term to help control allergy symptoms. 

How to take cetirizine

• Timing: Take cetirizine once a day at the same time each day. You can take cetirizine with or without food. Swallow the tablet whole, with a glass of water.
• Limit drinking alcohol while you are taking cetirizine. It may increase your chance of side effects such as sleepiness.  
• Missed dose: It is not harmful if you miss your cetirizine dose. If you forget to take your dose, and you usually take it regularly, take it as soon as you remember that day. If it is less than 12 hours for your next dose, just take the next dose at the right time. Do not take double the dose.

Precautions before starting cetirizine

• Are you are pregnant, trying for a baby or breastfeeding?
• Do you have epilepsy?
• Do you have any problems with the way your kidneys work?
• Are you taking or using any other medicines? This includes any medicines that you can buy without a prescription, as well as herbal and complementary medicines.

If so, it’s important that you tell your doctor or pharmacist before you start cetirizine. Sometimes a medicine isn’t suitable for a person with certain conditions, or it can only be used with extra care.

What are the side effects of cetirizine?

Like all medicines, cetirizine can cause side effects, although not everyone gets them. Often side effects improve as your body adjusts to the new medicine.

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If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:

• A headache, sore throat, abdominal pain, fatigue, drowsiness, or coughing. Other side effects are uncommon.
• Generally does not cause drowsiness, although more likely to do so at higher dosages. Caution should be exercised before driving or operating machinery until the full effects of cetirizine are known.
• The dosage of cetirizine should be reduced in kidney disease and caution should be exercised when cetirizine is used in people with seizure disorders.
• Cetirizine, like all other antihistamines, may decrease the response to skin prick tests. Discontinue cetirizine at least 72 hours prior to skin testing.
• Weigh up the risks versus benefits before using during pregnancy and breastfeeding.

Note: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. View complete list of side effects

4. Bottom Line

Cetirizine is an antihistamine that effectively treats allergic-type reactions such as hay fever or skin reactions caused by insect bites. Although drowsiness with cetirizine is uncommon, cetirizine is more likely than loratadine to cause drowsiness.

5. Tips

• May be taken with or without food. Cetirizine is usually taken once a day. During the pollen season, your doctor may advise you to take it every day if you suffer from seasonal allergic rhinitis.
• Although cetirizine is unlikely to make you drowsy, some people are susceptible to this effect, especially if they are taking dosages at the upper end of the recommended dosage range. Do not drive or operate machinery if cetirizine makes you drowsy. Alcohol and other sedative-like drugs may cause additional reductions in alertness if used with cetirizine.
• Seek urgent medical advice if you have hives and develop swelling of the face, throat, or tongue, dizziness, drooling, difficulty speaking, or shortness of breath.
• Cetirizine is not a substitute for epinephrine which is used for the treatment of severe allergies and anaphylaxis.
• Cetirizine is available as a suspension for adults and children who have difficulty swallowing tablets.
• See your doctor if your mild allergy symptoms have not improved after three days of treatment with cetirizine, or if your hives persist for more than six weeks despite taking cetirizine.
• Discontinue cetirizine once your allergy symptoms have resolved.
• Do not take cetirizine during pregnancy or while breastfeeding unless on the advice of your doctor.

6. Response and effectiveness

• Peak concentrations are reached within one hour of administration of cetirizine tablets or syrup. The onset of effect occurs within 20 minutes in 50% of people and within an hour in 95%.
• Effects persist for at least 24 hours following a single dose of cetirizine. No tolerance has been found to cetirizine's antihistaminic effect. Once discontinued, the skin recovers its normal reactivity to histamine within three days.
• Taking 10mg of cetirizine is more effective than taking 5mg; taking 20mg appears not to provide any additional effect.
• Food has no effect on the overall absorption of cetirizine; however, it may increase the time it takes for peak levels of cetirizine to be reached in the blood.

7. Interactions

Medicines that interact with cetirizine may either decrease its effect, affect how long it works for, increase side effects, or have less of an effect when taken with cetirizine. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed.

Common medications that may interact with cetirizine include:

• anticonvulsants, such as fosphenytoin, lamotrigine, levetiracetam, phenytoin, or valproic acid
• antidepressants, such as clomipramine, escitalopram, or fluvoxamine
• antipsychotics, such as aripiprazole, chlorpromazine, or clozapine
• baclofen
• barbituates, such as butabarbital
• benzodiazepines, such as diazepam or temazepam
• benztropine
• bupropion
• buspirone
• cannabis and cannabinoids
• clonidine
• HIV medications such as darunavir, lopinavir, ritonavir, or saquinavir
• duloxetine
• ketamine
• lithium
• monoamine oxidase antidepressants, such as phenelzine, isocarboxazid
• mumps skin test antigen
• opioids, such as codeine, fentanyl, hydrocodone
• other antihistamines, such as azatadine, azelastine, or brompheniramine
• sleeping medications, such as zolpidem
• St John's wort
• topiramate
• voriconazole.

Alcohol may increase the risk of sedation with cetirizine.

Note that this list is not all-inclusive and includes only common medications that may interact with cetirizine. You should refer to the prescribing information for cetirizine for a complete list of interactions.

More about cetirizine

Patient resources

Other brands

Zyrtec, Quzyttir

Professional resources

Related treatment guides

References

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use cetirizine only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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