How Much Cetirizine Can Be Used?

Patient Presentation
A 6-year-old male came to clinic with a history of seasonal allergic rhinitis. Loratadine usually controlled his symptoms well, but this spring seemed to be worse than usual. His mother was giving him the medicine in the morning but by the evening he was having increased sneezing, watery eyes and his mouth was itching. He was having problems sleeping also because of the increased rhinorrhea and was more tired during the day. “I started giving him some Benadryl® at night to try to help him sleep,” she said. “The medicine is just not working.” The past medical history revealed some mild atopic eczema, two episodes of bronchospasm that responded to albuterol, and seasonal allergic rhinitis that was worse in the spring and fall. The family history was positive for exercise-induced asthma and seasonal allergies on both sides of the family. The review of systems was negative.

The pertinent physical exam showed a healthy boy with normal growth parameters. His eyes had allergic shiners and cobblestoning of the palpebral conjunctiva. There was mild redness of the bulbar conjunctiva bilaterally. His nose showed copious clear rhinorrhea with boggy turbinates without polyps. His lungs were clear. His skin had some mild keratosis pilaris on the upper arms. The rest of his examination was negative.

The diagnosis of seasonal allergic rhinitis and conjunctivitis not responding to his regular antihistamine treatment was made. The physician recommended changing to cetirizine and to use more medicine than what was on the label. He said, “The allergists like this medicine because it seems to work without many side effects, and you can use alot of this medicine. We can increase it to help his symptoms.” He went on, “For your son, I would start with 20 mg or two tablets in the morning, but after a few days if he is still having problems, add another tablet at night. If that isn’t working then you can add another tablet. That would be 40 mg a day. If you look at the label it will tell you only 10 mg a day. It’s a very safe medicine, but let’s start low and see how much he needs to help his symptoms. As things improve with the summer then you can decrease the amount of the medicine too.” The physician also prescribed antihistamine eye drops to help control the eye symptoms, but his mother did not want to use nasal steroids at that time. “Call me in about 5 days or so and let me know how things are going, and we can decide if he needs more of the medicine and also about continuing the eye drops,” he instructed. The patient’s clinical course over the next two weeks showed him needing 20 mg BID to control his symptoms but he was now not using his eye drops. He was not having any medicine side effects and was able to sleep and play. Over the next few months, the boy was able to decrease the cetirizine to 10 mg a day in the summer, but needed 20 mg BID of cetirizine again in the fall.

Antihistamine medications have been available for over 70 years. The original H1-antihistamines, while effective in treated allergic rhinitis, urticaria and other allergic problems, easily penetrated the blood-brain barrier and caused somnolence. The newer, second generation H1-antihistamines have much less somnolent side effects because of poor penetrance.

Fexofenadine (Allegra®), desloratadine (Claritin®) and levocetirizine (Zyrtec®) are commonly used H1-antihistamines in the US today. Previously Astemazole (Hismanal®) and Terfanadine (Seldane®) were used but were withdrawn because of problems with cardiac arrhythmias with a propensity to prolong the QT interval. Fexofenadine in studies has the same somnolence producing effect as placebo. Desloratadine and cetirizine both can have some sedative effects.

Cetirizine is extensively and rapidly absorbed by the gut allowing a rapid onset of action. It interacts with target receptors at effective concentrations, and organs where it would not be effective or toxic are avoided. There is no hepatic metabolism (thus avoiding many potential drug-drug interactions) and the drug is excreted unchanged by the kidney. The half-life is about 10.5 hours in adults. Cetirizine has higher binding affinity for receptors than other similar drugs thus it has “…a more potent, faster onset and longer duration of action…” when used for seasonal allergic rhinitis. “…[T]here is evidence that continuous treatment with cetirizine is more effective than on-demand treatment in achieving significantly greater inflammatory and clinical control in [allergic rhinitis] patients.” Cetirizine does not have cardiotoxic side effects, and is a pregnancy category B medicine ( = without harm to animal fetus and no human studies available). It is excreted in breast milk therefore is not recommended during lacatation. Cetirizine is contraindicated for people with known hypersensitivity to its components or hydroxyzine.

Learning Point
Cetirizine is a safe and effective medication, and because of this some allergists will use it off label in higher doses. As with any time a medicine is used off-label, it is important to monitor the patient closely for efficacy and especially for potential side effects. It is the human metabolite of hydroxyzine (Atarax®) that is used for severe urticaria/pruritis and seasonal allergic rhinitis.
Normal dosing for cetirizine is:
6 months-2 years, 2.5 mg daily to BID
2-5 years, 2.5 mg daily to BID
6-11 years, 5-10 mg daily to BID
> 12 years, 5-10 mg daily to BID

Hydroxyzine is often used at doses of 2 mg/kg/day up to 75 mg BID. Hydroxyine to cetirizine as an equivalent is 25 mg of hydroxyzine to 10-20 mg cetirizine equivalent (personal communication with pediatric allergist).

Thus for a hydroxyzine dose of 75 mg/dose, the cetirizine dose would be 30-60 mg/dose. Using an average of 20 kg weight for the 6 year old above, the dose would be 16-30 mg/dose. Thus the physician above starting at 20 mg once a day was within this range and the amount the child needed to control his symptoms (40 mg/day) was also within this range.

A reported overdose in an adult of 150 mg caused somnolence but no other problems. An overdose in an 18 month old patient of ~180 mg caused restlessness, irritability and then drowsiness. There were no other problems.

Questions for Further Discussion
1. What are indications for use of intranasal steroids for seasonal allergic rhintis?
2. What are indications for use of antihistamine eye drops for allergic conjunctivitis?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for these topics: Allergies and Cough and Cold Medicines.

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

To view videos related to this topic check YouTube Videos.

Cetirizine. RxList. Available from the Internet at (rev. 5/16/2007, cited 5/26/2014).

Zhang L, Cheng L, Hong J. The clinical use of cetirizine in the treatment of allergic rhinitis. Pharmacology. 2013;92(1-2):14-25.

Church MK, Church DS. Pharmacology of antihistamines. Indian J Dermatol. 2013 May;58(3):219-24.

ACGME Competencies Highlighted by Case

  • Patient Care
    1. When interacting with patients and their families, the health care professional communicates effectively and demonstrates caring and respectful behaviors.
    2. Essential and accurate information about the patients’ is gathered.
    3. Informed decisions about diagnostic and therapeutic interventions based on patient information and preferences, up-to-date scientific evidence, and clinical judgment is made.
    4. Patient management plans are developed and carried out.
    5. Patients and their families are counseled and educated.
    8. Health care services aimed at preventing health problems or maintaining health are provided.

  • Medical Knowledge
    10. An investigatory and analytic thinking approach to the clinical situation is demonstrated.
    11. Basic and clinically supportive sciences appropriate to their discipline are known and applied.

  • Practice Based Learning and Improvement
    12. Evidence from scientific studies related to the patients’ health problems is located, appraised and assimilated.
    13. Information about other populations of patients, especially the larger population from which this patient is drawn, is obtained and used.

  • Interpersonal and Communication Skills
    17. A therapeutic and ethically sound relationship with patients is created and sustained.

  • Systems Based Practice
    23. Differing types of medical practice and delivery systems including methods of controlling health care costs and allocating resources are known.


    Donna M. D’Alessandro, MD
    Professor of Pediatrics, University of Iowa Children’s Hospital