Cetirizine

Structural formula
1: 1 mixture of ( R ) - (-) - cetirizine (top) and ( S ) - (+) - cetirizine (bottom), see stereochemistry
General
Non-proprietary name	Cetirizine
other names	( RS ) -2 - {[4- (4-chlorophenyl) phenylmethyl] -1-piperazinyl} ethoxyacetic acid rac -2 - {[4- (4-chlorophenyl) phenylmethyl] -1-piperazinyl} ethoxyacetic acid (±) -2 - {[4- (4-Chlorophenyl) phenylmethyl] -1-piperazinyl} ethoxyacetic acid DL -2 - {[4- (4-chlorophenyl) phenylmethyl] -1-piperazinyl} ethoxyacetic acid
Molecular formula	C 21 H 25 ClN 2 O 3 [cetirizine] C 21 H 25 ClN 2 O 3 · 2 HCl [cetirizine dihydrochloride]
External identifiers / databases
CAS number 83881-51-0 [( RS ) -Cetirizine] 83881-52-1 [( RS ) -Cetirizine · Di hydrochloride ] 130018-77-8 [( R ) -Cetirizine] 130018-87-0 [( R ) -Cetirizine · dihydrochloride] EC number 695-115-1 ECHA InfoCard 100.223.545 PubChem 2678 ChemSpider 2577 DrugBank DB00341 Wikidata Q423075
Drug information
ATC code	R06 AE07
Drug class	Antihistamines of ethylenediamine -type
properties
Molar mass	388,89 g · mol -1 [( RS ) -Cetirizin] 461.81 g · mol -1 [( RS ) -Cetirizin · dihydrochloride]
Melting point	110-115 ° C [( RS ) -Cetirizine] 225 ° C [( RS ) -Cetirizine · dihydrochloride] 229.3 ° C [( R ) -Cetirizine · dihydrochloride]
safety instructions
Please note the exemption from the labeling requirement for drugs, medical devices, cosmetics, food and animal feed GHS labeling of hazardous substances Caution H and P phrases H: 302 P: no P-phrases
Toxicological data	365 mg kg −1 ( LD 50 ,  rat ,  oral , dihydrochloride)
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Cetirizine is a drug from the group of antihistamines of the 2nd generation that is used to relieve symptoms of allergic diseases . The substance was developed on the basis of hydroxyzine , a first generation antihistamine. Chemically, cetirizine is one of the derivatives of ethylenediamine or piperazine .

application

Cetirizine is used to relieve the symptoms of allergies , neurodermatitis , hives and itching and other allergic skin reactions. Cetirizine can also be taken for hay fever and allergic conjunctivitis . Among the newer H ₁ antihistamines, cetirizine, along with loratadine, is one of the most frequently used antiallergic drugs .

In domestic cats with atopic dermatitis , cetirizine has no antipruritic effect.

Mechanism of action

The effect of histamine on the H ₁ receptor is interrupted. Histamine causes the typical hay fever symptoms such as watery eyes and a stuffy nose, but also itchy skin. The second generation antihistamines have the advantage that very little active substance reaches the central nervous system , since the drug molecule is present as a zwitterion under physiological conditions and the blood-brain barrier can hardly be crossed. Compared to antihistamines of the first generation, sedating side effects such as B. Fatigue occurs less often.

Maximum plasma concentrations are reached 0.5 to 1.5 hours after oral administration. The plasma half-life is approximately 9 and 10 hours, respectively. 65% of the excretion is via the kidneys, mainly in unchanged form. Cetirizine has linear kinetics over the range of 5 to 60 mg.

Side effects

Some (about 1 in 100 people) reported tiredness , headache , hallucinations , drowsiness or dry mouth .

In addition, cetirizine, like loratadine and azelastine, is suspected of triggering cardiac arrhythmias in certain predispositions - but not as often as terfenadine , where this side effect is known and proven.

Interactions

At therapeutic doses of cetirizine, no clinically significant drug interactions were found in connection with the ingestion of alcohol - at a plasma concentration of 0.5 grams / liter (0.5 "per mille") .

Based on the pharmacokinetics , pharmacodynamics and tolerability profile of cetirizine, no interactions with this antihistamine are expected. In fact, neither pharmacodynamic nor significant pharmacokinetic interactions were reported in interaction studies performed, especially with pseudoephedrine and theophylline (400 mg / day). The extent of absorption of cetirizine is through food intake is not reduced, although the rate of absorption is decreased.

Stereochemistry

Cetirizine is a 1: 1 mixture ( racemate ) of the ( R ) - (-) - enantiomer and ( S ) - (+) - enantiomer. Through a resolution can be selectively active ( R ) - enantiomer ((-) - eutomer win of cetirizine, which as) levocetirizine is called. The importance of the enantiomeric purity of the synthetically produced active substances was given attention by the development of levocetirizine, because the two enantiomers of a chiral drug almost always show different pharmacology and pharmacokinetics. In the past, this was often ignored due to a lack of knowledge of stereochemical relationships.

However, due to the lack of comparative studies, levocetirizine has not yet been clearly superior to racemic cetirizine in terms of effectiveness, even if individual studies indicate this.

Trade names

Monopreparations

Cerchio (IT), Cerzin (CH), Cetallerg (CH), Cet eco (CH), Ceterifug (D), Cetiderm (D), CetiLich (D), Ceti-Puren (D), Cetirigamma (D), Cetrin ( CH), Cetryn (TR), Helvecin (CH), Hista-X (CH), RatioAllerg (A), Reactine (D), Tirizin (A), Triofan Allergie (CH), Zyrtec (D, A, CH), numerous generics (D)

Combination preparations

Reactine duo (D)

Individual evidence

1. ↑ ^{a b c} The Merck Index . An Encyclopaedia of Chemicals, Drugs and Biologicals . 14th edition, 2006, p. 334, ISBN 978-0-911910-00-1 .
2. ↑ ^{a b c} data sheet cetirizine dihydrochloride from Sigma-Aldrich , accessed on March 16, 2011 ( PDF ).
3. ↑ K. Wildermuth, S. Zabel, RA Rosychuk: The efficacy of cetirizine hydrochloride on the pruritus of cats with atopic dermatitis: a randomized, double-blind, placebo-controlled, crossover study. In: Veterinary dermatology. Volume 24, number 6, December 2013, pp. 576–81, e137, doi : 10.1111 / vde.12067 , PMID 24112588 .
4. ↑ Johnson & Johnson: Product Information Reactine duo 5 mg / 120 mg prolonged-release tablets. As of December 2018.
5. ↑ ODDB.org: Information for professionals on Cetirizin Actavis® 10 mg ( Memento of the original from November 25, 2013 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , accessed June 21, 2013. 
6. ↑ S. Haffner et al. (2002): Adverse drug reactions: QT prolongation and torsade de pointes arrhythmias. In: German Medical Weekly . Vol. 127, pp. 1022-1024. doi : 10.1055 / s-2002-28319 .
7. ^ Woosley RL, Chen Y, Freiman JP, Gillis RA. Mechanism of the cardiotoxic actions of terfenadine. J Am Med Ass. 1993; 269 : pp. 1532-1536, PMID 8445816 .
8. ↑ Zyrtec: Summary of Product Characteristics, as of October 8, 2008 on the website of the European Medicines Agency EMEA (PDF, 323 kB), accessed on August 18, 2009.
9. ↑ EJ Ariëns (1984): Stereochemistry, a basis for sophisticated nonsense in pharmacokinetics and clinical pharmacology. In: European Journal of Clinical Pharmacology . Vol. 26, pp. 663-668, doi : 10.1007 / BF00541922 .
10. ↑ GM Walsh (2008): A review of the role of levocetirizine as an effective therapy for allergic disease. In: Expert Opin Pharmacother . Vol. 9, pp. 859-867, PMID 18345961 .
11. ↑ C. Bachert (2006): Levocetirizine vs. Cetirizine: An evidence-based differentiation based on pharmacology and clinic. In: Allergology. Vol. 29, pp. 268-273.

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