Cetirizine • Dosage & Side Effects

The allergy drug cetirizine has a rapid and long-lasting effect on allergies. That is why it is often used in people with hay fever to relieve the annoying symptoms. What role does histamine play in the effectiveness of the drug and what are the side effects – apart from the typical tiredness?

To treat allergies such as hay fever, the well-tolerated and quickly effective active ingredient cetirizine is often prescribed. Since it inhibits the effects of histamine in the body, it helps against allergic reactions such as a runny nose and itching. However, many people complain of increased fatigue after taking it as a side effect of the drug.

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What is cetirizine and when is it used?

As an effective drug against allergies, cetirizine is often used. The most common form of allergy is hay fever, here the antiallergic acts against the typical symptoms of watery eyes, runny nose or a blocked nose due to swelling of the mucous membranes. Allergic skin reactions such as itching, redness and wheals can also be alleviated with cetirizine. This also applies to allergic hives (urticaria). Since the effect begins within 10-30 minutes, acute symptoms can be alleviated quickly.

How long the treatment lasts depends on the symptoms and their causes. During an acute phase of hay fever, several weeks are often sufficient, while those affected also suffer from asthma-like symptoms, requiring treatment lasting several months. Children, on the other hand, should only take cetirizine for a short time. The exact duration of treatment will be agreed by the doctor after the diagnosis.

effect of the allergy drug

In the event of an allergic reaction, the body reacts to an exogenous substance with an excessive immune response, releasing the messenger substance histamine, among other things. As a result, symptoms such as a runny nose, itchy eyes, water retention in the tissue (edema) or skin rashes can occur. The active ingredient cetirizine blocks specific histamine-1 receptors in the body, which is why it is also known as an H1 antihistamine. Due to the blockade, histamine can only bind to the receptors to a significantly reduced extent in the event of an allergic reaction and develop its effect. At the same time, the active ingredient prevents immediate reactions on the skin and the storage of water in the tissue.


The active ingredient is considered a third-generation antiallergic, so it is a further development of the antiallergic drug cetirizine. Levocetirizine also inhibits histamine receptors. The side effect profile is comparable to that of cetirizine.

Antiallergic dosage

The active ingredient cetirizine is available in the form of cetirizine dihydrochloride as film-coated tablets, lozenges, drops or juice in pharmacies. Since the effect of the anti-allergy drug lasts for a long time, it only needs to be taken once a day. Adults and children over 12 years of age take one film-coated tablet (10 mg) or 20 drops per day.

Children aged 2 to 12 years are given a lower dose depending on their body weight:

  • Less than 30 kg body weight: Half a film-coated tablet (5 mg) or five drops twice a day
  • over 30 kg body weight: One film-coated tablet a day (half a morning and half in the evening) or 10 drops twice a day

If the daily intake of the antiallergic is forgotten, the dose should not be doubled, but continued with the prescribed dose the next day. An overdose of the active substance can lead to drowsiness, dizziness, diarrhea and increased heart rate.

Instructions for taking

Cetirizine is not taken with meals, tablets should be swallowed whole with a glass of water. Those who suffer from severe tiredness and drowsiness can take it in the evening to cushion these side effects. Such patients should take special care when driving or using machines while taking it. Alcohol consumption may affect alertness if cetirizine is taken at the same time.

Possible side effects of cetirizine

The antiallergic is one of the second-generation drugs and crosses the blood-brain barrier in the brain to a significantly reduced extent compared to the first generation. Nevertheless, many complain of fatigue, drowsiness and drowsiness as side effects after use.

In addition, the following side effects are common:

In rare cases, neurological side effects can also occur after taking cetirizine, for example aggressive behavior, hallucinations or confusion. Some patients also report cramps, insomnia, weight gain or palpitations (tachycardia). Further information is contained in the leaflet or can be obtained from the pharmacist. Anyone who notices undesirable effects while using cetirizine should seek medical help immediately.

Interactions with other drugs are not known to date. If antihistamines and heparin are taken at the same time, the effect can be weakened, since heparin causes salt formation in the body.

Contraindications: when should cetirizine not be used?

The active ingredient is approved for children from the age of one year, before that it may not be used. Even if hypersensitivity is known, cetirizine must not be taken. Since the active ingredient is mainly excreted via the kidneys, patients with severe kidney diseases should also not take it. In addition, people with a lactase deficiency, glucose-galactose malabsorption or galactose intolerance should avoid taking it.

pregnancy and breast feeding period

Animal studies have so far not been able to demonstrate any teratogenic effects. Nevertheless, cetirizine should only be taken during pregnancy after consulting a doctor. It is also not recommended to take the active ingredient while breastfeeding, as it has passed into breast milk in animal experiments. However, there is still no corresponding evidence for humans.

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Source: Lifeline | Das Gesundheitsportal by www.lifeline.de.

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