Cetirizine dihydrochloride is a chemical compound, an antihistamine, selective peripheral histamine H1 receptor antagonist, first generation H1 metabolite of hydroxyzine with inhibitors on eosinophil chemotaxis.

The name describes the structure of the molecule:

• Cetirizine. Cetirizine is a second-generation antihistamine used in the treatment of hay fever, allergies, angioedema and urticaria. It is known to be less sedative than the older first-generation antihistamines. It works by blocking the action of histamine, a substance in the body that causes allergic symptoms.
• Dihydrochloride. Dihydrochloride refers to a type of salt formed when two hydrochloric acid (HCl) molecules are attached to a parent molecule. In the context of cetirizine dichlorhydrate, this means that two hydrochloride groups are attached to a cetirizine molecule. This form of the drug is often used because it is stable, easy to manufacture and store, and can be easily absorbed by the body when taken orally.

The synthesis process takes place in different steps:

• Piperazine production. The first step involves the production of piperazine, a cyclic organic compound by different methods, including the reaction of ethylene dichloride with ammonia.
• Reaction with methyl chloroformate and ethyl acetoacetate. Piperazine is reacted with methylchloroformate and ethyl acetoacetate in a multi-step process to produce a compound called cetirizine.
• Conversion to cetirizine hydrochloride. Cetirizine is converted to cetirizine dihydrochloride through a reaction with hydrochloric acid. This process involves the addition of two hydrochloride groups to the cetirizine molecule.

It occurs in the form of a white-beige powder

What it is for and where

Medical

Take only under medical supervision

It is a second-generation nonsedating antihistamine drug used as symptomatic treatment for chronic urticaria, seasonal and permanent allergic rhinitis, atopic dermatitis, and also used as an adjunct in seasonal asthma and allergic cough. 

Both cetirizine and levocetirizine showed significant improvement in nasal peak expiratory flow compared with the placebo group, and ceterizine appeared to be more effective than levocetirizine.(1) , enantiometer R of cetirizine.

This preliminary study demonstrated that 4-week treatment with cetirizine for the treatment of seasonal allergic rhinitis was able to significantly improve quality of life. Treatment with cetirizine also significantly reduced symptom severity in Italian children with seasonal allergic rhinitis and was safe (2).

Early treatment of symptomatic COVID-19 patients with antihistamines and azithromycin and administration of antihistamines in asymptomatic, high-risk patients had excellent results in the population by reducing mortality rates, hospitalizations, and ICU admissions regardless of patient age and risk factors (3).

In 2019, intravenous cetirizine was approved for the treatment of acute urticaria, and compared with intravenous diphenhydramine, cetirizine has fewer contraindications and lower risk on elderly patients (4).

Like all drugs it can cause side effects. Always ask the physician.

Cetirizine Dihydrochloride studies

Typical optimal characteristics of the commercial product Cetirizine dihydrochloride

Appearance	Powder fine, white tp beige
Solubility	H2O: 5 mg/mL, clear
Flash point	281.6ºC
Density	1.237 g/cm3
Boiling Point	542.1ºC at 760 mmHg
Melting Point	110-115ºC
PSA	53.01000
LogP	3.82600
Hazard Class	6.1(b)

• Molecular Formula:  C₂₁H₂₇Cl₃N₂O₃
• Molecular Weight:  461.8 g/mol
• CAS: 83881-52-1
• UNII 64O047KTOA
• MDL number MFCD00941428 
• PubChem Substance ID 329775040
• EC Number: 620-533-8
• DSSTox Substance ID: DTXSID2044268
• InChi= 1S/C21H25ClN2O3.2ClH/c22-19-8-6-18(7-9-19)21(17-4-2-1-3-5-17)24-12-10-23(11-13-24)14-15-27-16-20(25)26;;/h1-9,21H,10-16H2,(H,25,26);2*1H
• InChi Key      PGLIUCLTXOYQMV-UHFFFAOYSA-N
• SMILES    C1CN(CCN1CCOCC(=O)O)C(C2=CC=CC=C2)C3=CC=C(C=C3)Cl.Cl.Cl
• IUPAC 2-[2-[4-[(4-chlorophenyl)-phenylmethyl]piperazin-1-yl]ethoxy]acetic acid;dihydrochloride
• ChEBI    3562

Synonyms: 

• Cetirizine Dihydrochloride
• Dihydrochloride, Cetirizine
• (2-(4-((4-Chlorophenyl)phenylmethyl)-1-piperazinyl)ethoxy)acetic Acid

References_______________________________________________________________________

(1) Lee CF, Sun HL, Lu KH, Ku MS, Lue KH. The comparison of cetirizine, levocetirizine and placebo for the treatment of childhood perennial allergic rhinitis. Pediatr Allergy Immunol. 2009 Aug;20(5):493-9. doi: 10.1111/j.1399-3038.2008.00816.x.

(2) Benazzo M, Leonardi S, Corsico A, Licari A, Miraglia Del Giudice M, Peroni D, Salpietro C, Marseglia GL, Ciprandi G. Cetirizine modifies quality of life and symptoms in children with seasonal allergic rhinitis: a pilot study. Acta Biomed. 2020 Jun 17;92(1):e2021003. doi: 10.23750/abm.v92i1.9948.

(3) Morán Blanco JI, Alvarenga Bonilla JA, Homma S, Suzuki K, Fremont-Smith P, Villar Gómez de Las Heras K. Antihistamines and azithromycin as a treatment for COVID-19 on primary health care - A retrospective observational study in elderly patients. Pulm Pharmacol Ther. 2021 Apr;67:101989. doi: 10.1016/j.pupt.2021.101989. 

(4) Blaiss MS, Bernstein JA, Kessler A, Pines JM, Camargo CA Jr, Fulgham P, Haumschild R, Rupp K, Tyler T, Moellman J. The Role of Cetirizine in the Changing Landscape of IV Antihistamines: A Narrative Review. Adv Ther. 2021 Dec 4. doi: 10.1007/s12325-021-01999-x.