Can You Overdose On Zyrtec (Cetirizine)?

In our latest question and answer, the pharmacist discusses whether or not it is possible to overdose on Zyrtec (cetirizine).

Question

Is it possible to overdose on Zyrtec? Are there any side effects I should be aware of?

Asked by Jeremy On Jul 31, 2018

Answered by
Medical Content Reviewed By PharmacistAnswers Staff

On Jul 31, 2018

It is possible to overdose on Zyrtec (cetirizine), just like any medication. Fortunately, if you accidentally take an extra dose or two, the side effects are relatively mild and are generally not serious.


The prescribing information for Zyrtec notes two cases studies in which an overdose was observed in an adult and pediatric patient:

  • In one case study of an adult overdose, 150mg was taken (15 tablets) and only minimal effects were reported. It was noted that the patient was 'somnolent' (i.e. sleepy), but they did not display any other serious clinical signs of toxicity or abnormal blood chemistry.
  • An 18 month old pediatric patient accidentally ingested 180 mg (18 tablets). No serious symptoms were reported aside from restlessness and irritability, followed by drowsiness.


The package insert for Zyrtec goes on to say the following regarding overdose:

"Should overdose occur, treatment should be symptomatic or supportive, taking into account any concomitantly ingested medications. There is no known specific antidote to cetirizine hydrochloride."

Although most cases studies report minimal side effects in regard to overdosing with Zyrtec, it is important to note that some individuals may be more susceptible to side effects than others. It is therefore important to consider all of the side effects that Zyrtec can cause, such as:

  • Dry mouth
  • Dry eyes
  • Constipation
  • Drowsiness
  • Increased heart rate
  • Cardiac effects
  • Headache
  • Hyperventilation
  • Central nervous system excitation


In any case involving an overdose, it would be prudent to contact the poison control center at 1-800-222-1222 or go to the emergency room.


Additional Information

There have been no deaths reported with Zyrtec overdose and such studies have only been completed in mice and rats.


The prescribing information gives the following data regarding lethal doses in rodents:

  • The acute minimal lethal oral doses was 237 mg/kg in mice. For a 100 pound adult, this translates to over 10,000 mg (1,000-10 mg tablets).
  • The acute minimal lethal oral doses was 562 mg/kg in rats. For a 100 pound adult, this translates to over 25,000 mg (2,500-10 mg tablets).


Although many cases of overdose are accidental, know that assistance is available if you or someone you know has suicidal thoughts or has spoken about overdosing on medication. The National Suicide Prevention Lifeline hotline is 1-800-273-8255.

About the Pharmacist

Dr. Brian Staiger Pharm.D

Dr. Brian Staiger is a licensed pharmacist in New York State and the founder of PharmacistAnswers.com. He graduated from the University At Buffalo with a Doctor of Pharmacy degree in 2010. He has been featured in numerous publications including the Huffington Post as well as a variety of health and pharmacy-related blogs. Please feel free to reach out to him directly if you have any inquiries or want to connect! He's answered thousands of medication and pharmacy-related questions and he's ready to answer yours! Brian.Staiger@PharmacistAnswers.com Office: 716-389-3076

About Zyrtec (Cetirizine)

Zyrtec (cetirizine) is a "second-generation" antihistamine, indicated for the treatment and prevention of perennial allergies, seasonal allergies and hives. At indicated doses (5mg and 10mg), it generally has a higher incidence of sedation than other second-generation antihistamines, such as Allegra (fexofenadine) and Claritin (loratadine). Nevertheless, it still causes less sedation than older, first-generation antihistamines such as Benadryl. Zyrtec is taken once daily, with an onset of action around one hour.

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