How cetirizine works
As a so-called H1 antihistamine, cetirizine blocks the docking sites (H1 receptors) of the body’s own messenger substance histamine – a substance that occurs everywhere in the body and is involved in normal concentrations in important processes such as the immune response, the production of stomach acid and the regulation of sleep. However, histamine also plays an important role in allergic reactions.
An allergic reaction is a hypersensitivity reaction of the immune system. The body reacts to contact with an actually harmless allergy trigger (allergen such as pollen, house dust or animal hair) with an excessive release of histamine in order to combat the supposedly dangerous allergen.
If histamine subsequently binds to its receptor, the typical symptoms of an allergy occur, such as increased blood flow to the tissue (redness and swelling), itching, watery eyes and even cramping of the airway muscles (bronchospasm).
By blocking the histamine receptor, cetirizine prevents the effects of histamine and thus alleviates the symptoms of an allergic reaction.
Absorption, breakdown and excretion
The active substance is excreted primarily via the kidneys. For this reason, the dosage must be reduced in people with kidney failure (renal insufficiency).
When is cetirizine used?
The areas of application (indications) of the antihistamine are
- Relief of symptoms of chronic hives (urticaria)
- Relief of symptoms of the eyes (allergic conjunctivitis) and nose (hay fever)
How cetirizine is used
Cetirizine is most commonly taken in tablet form. However, cetirizine drops and cetirizine juice are also available. The cetirizine dosage is usually ten milligrams a day, less for children and people with kidney problems.
It is usually taken once a day according to the doctor’s instructions. Food slows down the rate of absorption (and therefore the onset of action), but not the amount of active ingredient absorbed.
What are the side effects of cetirizine?
In general, the active ingredient is well tolerated. Frequently (i.e. in one to ten percent of patients), cetirizine causes tiredness, sedation and gastrointestinal complaints (at higher doses).
Less than one percent of those treated develop headaches, dizziness, insomnia, aggressiveness or dry mouth as side effects.
What should I bear in mind when taking Cetirizine?
Contraindications
Cetirizine must not be used in the following cases
- hypersensitivity to the active substance or any of the other ingredients of the medicine
- severe renal dysfunction
- children under two years of age
Interactions
No interactions with other medicines are known to date.
Cetirizine suppresses the skin’s reaction to allergy tests. Therefore, the medication should be discontinued three days before such a test in order not to falsify the result.
Experts recommend avoiding alcohol during treatment with antihistamines such as cetirizine.
Ability to drive and operate machinery
In contrast to many other antihistamines, cetirizine has only a mild sedative effect. Nevertheless, caution is required when driving a motor vehicle and operating machinery. Patients should be aware of their body’s individual reaction to the active substance (tiredness, dizziness, etc.).
Age restriction
Use in children under two years of age is not recommended.
Pregnancy and breastfeeding
Cetirizine can be used during breastfeeding after consultation with a doctor. However, there are no data on the transfer of the active substance into breast milk in humans. In principle, long-term use of antihistamines could cause restlessness, sedation and other symptoms in breastfed children. In the specific case of cetirizine, however, this is rather unlikely. According to experts, the active ingredient can therefore be taken while breastfeeding without the need to discontinue breastfeeding.
How to obtain medication with cetirizine
Medicines containing cetirizine are available over-the-counter in pharmacies in Germany, Austria and Switzerland.
How long has cetirizine been known?
Cetirizine has not been known for very long. After taking a first-generation antihistamine, cetirizine was found as a conversion product in the body of those affected. Clinical studies then showed that the new substance had a comparable effect with fewer side effects.
The active ingredient is therefore better tolerated than older preparations and has largely replaced their use as medication for allergic reactions.
