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Zyrtec (Cetirizine)

Zyrtec (Cetirizine)


Cetirizine, sold under the brand name Zyrtec among others, is a second-generation antihistamine used to treat allergic rhinitis (hay fever), dermatitis, and urticaria. It is taken by mouth. Effects generally begin within an hour and last for about a day.

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Zyrtec (Cetirizine) is an anti-histamine pill. It is new and selective – it means it only blocks H-1 receptors.  Histamine is secreted through eosinophils, and Zyrtec decreases the level of their involvement. It decreases the manifestations of immune reactions like skin rash or bronchial constriction, like in asthma.

It is very effective in form of pills or capsules – two thirds of Zyrtec (Cetirizine) are excreted unchanged, it does not involve in metabolism. There is no strong correlation between taking Zyrtec and eating or even drinking moderate amounts of alcohol (the influence of alcohol was not studied profoundly). Taking this medicine with big amounts of food creates mechanical barrier to the absorption of Cetirizine, but does not impact its absorption and properties.

Zyrtec (Cetirizine) is widely used to treat allergic rhinitis, season allergies, skin rush of allergic etiology, eases symptoms like sneezing, rhinorrhea, itching in the nose.


Naturally, Zyrtec (Cetirizine) should not be taken in patients with increased sensitivity to Cetirizine or its components, or any Piperazine derivatives.  Also patients with severe kidney disorders should withhold from taking it, but these two contraindications are rather a formality than something you will meet in the real life. In general, the medication is very well tolerated and shows a very small scope of side effects.

Zyrtec (Cetirizine) starts acting at a dose 5 mg, and its action can be enhanced by increasing the dose up to 60 mg. It makes no sense to take more than 60 mg, if you have taken 60 and it still does not show any effect you should consider alternative anti-histamine or corticosteroid.

Normal dose at which you should see the effect is 10 mg.

In elderly patients the medication is excreted more slowly, so the time between administration can be increased or supportive dose decreased.

Itching or skin rash can appear after you stop taking Zyrtec (Cetirizine) even if they were absent before.

Zyrtec (Cetirizine) is present in the breastmilk in concentrations that are approximately quarter from the blood plasma concentrations.

Although there was no evidence that the medication can cause any damage to the baby, but because it is present in the breastmilk it is recommended not to take it when breastfeeding, or take it only when the dangers to mothers’ health exceed the possible harm to the baby.

More importantly, Zyrtec (Cetirizine) does not influence the speed of reaction, does not affect ability to operate machinery. Many older anti-histamine medications caused sleepiness and slowed down reactions.

The trials were made on the dosage of 10 mg however.


Zyrtec (Cetirizine) cannot be effectively cleared from bloodstream via hemodialysis. Therefore, it is not recommended to increase the amount of the pills taken unless absolutely necessary.

If the initial dose of 10 mg was not effective – consult your doctor before considering increasing the dose – perhaps you will have to change the medication to other antihistamine or corticosteroid.

Side effects

Trials have shown that taking Zyrtec (Cetirizine) can cause following symptoms:

Headaches, dizziness (it was insignificantly bigger than in placebo group)

tiredness, eye accommodation disorders.

A patient taking Zyrtec (Cetirizine) may complain about the feeling of dryness in the mouth.

In children from six months to twelve years of age the following symptoms were noticed:

Diarrhea, sleepiness, rhinitis, tiredness.

In children from six months to twelve years of age the following symptoms were noticed:

Diarrhea, sleepiness, tiredness.

Pharmacological interaction

Zyrtec (Cetirizine) does not interact with most known drugs.

Theoretically, based on pharmacokinetics, pharmacodynamics and tolerance of Zyrtec, the interactions with other substances are unlikely.

In practice, Cetirizine has been tested for interaction with many substances, namely there was no interaction, neither pharmacokinetic nor pharmacodynamical, when it was simultaneously taken with pseudoephedrine or theophylline.

Simultaneous use of Zyrtec with kethonazole and macrolides did not cause clinically significant changes to the ECG.

There is no evidence that simultaneous use of Zyrtec with tranquillizers and sedatives can enhance any of them, it is not recommended to take them simultaneously, but that is more of a precaution.

Interaction with alcohol was tested at concentrations 0,5 g/l. No clinically significant interactions were noted, which makes Zyrtec (Cetirizine) one of the few anti-histamine drugs that can be taken with alcohol.

Patients with epilepsy should contact their doctors before taking Zyrtec for in patients with epilepsy this medication in rare cases may cause seizures.

In patients with impeded urination (suffering from spinal injuries or prostate hyperplasia) Zyrtec should be taken with care as it may increase the risk of urinary retention.

Patients who drive motor vehicles, engage in potentially dangerous work or service mechanized equipment should not exceed the recommended dosage and should take into account their own response to the drug.

In sensitive patients, concurrent administration of the drug with alcohol or other CNS suppressant agents may cause additional impairment of attention when performing potentially hazardous work.

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