Cetirizine: 6 things you should know
Medically reviewed by C. Fookes, BPharm. Last updated on Jan 10, 2019.
1. How it works
- Cetirizine is an antihistamine that works selectively on peripheral histamine-1 (H-1) receptors (these are histamine receptors that are located outside of the brain and spinal cord). Because it acts on peripheral histamine receptors, cetirizine is much less likely to cause drowsiness compared with some older antihistamines.
- Histamine is a chemical that is released by mast cells in response to an allergen, and it is responsible for many of the symptoms of an allergic reaction, such as swelling of the mucous membranes, sneezing, and itching. Cetirizine binds to histamine receptors and prevents histamine from having an effect at those receptors, which reduces the symptoms of an allergic reaction.
- Cetirizine belongs to the group of drugs known as antihistamines. Cetirizine may also be called an H1-antihistamine, a second generation antihistamine, or a nonsedating antihistamine.
- Used to treat allergic-type reactions due to perennial or seasonal allergic rhinitis (hay fever).
- Effective at controlling symptoms such as sneezing, itching, watery eyes, and runny nose that occur as a result of other respiratory allergens.
- Can provide relief from itching that occurs as a result of chronic urticaria (hives). Symptoms of hives include raised, red, itchy bumps, streaks, or blotches on the skin.
- May be used in the treatment of allergic conjunctivitis, insect bites, and other allergic skin disorders.
- Is less likely to cause sedation than older antihistamines.
- Can be taken once a day.
- May be given daily on a regular basis when allergens are most prevalent (such as during spring or summer).
- Cetirizine does not appear to interact with many drugs (theophylline slightly decreased the clearance of cetirizine).
- Cetirizine has been demonstrated to be safe in children older than 6 months.
- No dosage adjustment is required in liver disease.
- Available over-the-counter.
- Generic cetirizine is available.
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.
Notes: 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. For a complete list of all side effects, click here.
- 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.
- Cetirizine [Package Insert]. Revised 02/2017. Aidarex Pharmaceuticals LLC https://www.drugs.com/pro/cetirizine.html
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.
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- Drug class: antihistamines
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