Cetirizine hydrochloride
[CAS# 83881-52-1]

Identification

• Classification: API >> Antiallergic >> Antihistamine
• Name: Cetirizine hydrochloride
• Synonyms: 2-(2-{4-[(4-Chlorophenyl)(phenyl)-methyl]piperazino}ethoxy)acetic acid dihydrochloride
• Molecular Formula: C₂₁H₂₅ClN₂O₃.2(HCl)
• Molecular Weight: 461.81
• CAS Registry Number: 83881-52-1
• EC Number: 620-533-8
• SMILES: C1CN(CCN1CCOCC(=O)O)C(C2=CC=CC=C2)C3=CC=C(C=C3)Cl.Cl.Cl

Properties

• Solubility: 100mM (water), 107 mg/mL (DMSO)

Safety Data

• Hazard Symbols: GHS07;GHS08 Danger
• Risk Statements: H302-H317-H360
• Safety Statements: P203-P261-P264-P270-P272-P280-P301+P317-P302+P352-P318-P321-P330-P333+P317-P362+P364-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute toxicity	Acute Tox.	4	H302
Reproductive toxicity	Repr.	1B	H360
Skin sensitization	Skin Sens.	1	H317
Acute toxicity	Acute Tox.	4	H332
Skin irritation	Skin Irrit.	2	H315
Specific target organ toxicity - single exposure	STOT SE	3	H335
Serious eye damage	Eye Dam.	1	H318
Eye irritation	Eye Irrit.	2	H319
Skin corrosion	Skin Corr.	1A	H314
Skin corrosion	Skin Corr.	1B	H314
Skin corrosion	Skin Corr.	1C	H314
Skin sensitization	Skin Sens.	1B	H317
Chronic hazardous to the aquatic environment	Aquatic Chronic	3	H412

Discovery and Applications

The story of cetirizine hydrochloride begins in the research laboratories of pharmaceutical company UCB (Union of Chemistry of Belgium). Scientists aimed to create an antihistamine that was more effective and had fewer side effects than first-generation antihistamines such as diphenhydramine (Benadryl). These older drugs were often criticized for causing drowsiness, a significant drawback for many patients. By modifying the molecular structure of first-generation antihistamines, researchers developed cetirizine, which exhibits high efficacy in blocking H1 histamine receptors. These receptors are critical in mediating allergic reactions such as sneezing, itching, and hives. Cetirizine's unique properties allow it to effectively relieve these symptoms without significantly crossing the blood-brain barrier, thereby reducing the sedative effects common to earlier antihistamines. The U.S. Food and Drug Administration (FDA) approved cetirizine hydrochloride in 1995.

Cetirizine hydrochloride works by selectively inhibiting peripheral H1 receptors, which are activated during allergic reactions. When allergens trigger the release of histamines in the body, these chemicals bind to H1 receptors on certain cells, leading to inflammation, itching, and mucus production. Cetirizine blocks this binding process, preventing the typical allergic reaction. Because cetirizine is able to specifically bind to peripheral receptors, it minimizes effects on the central nervous system, which helps reduce sedation and cognitive impairment, which are common problems with first-generation antihistamines. This property makes it suitable for a wide range of patients, including those who need to stay alert throughout the day.

Cetirizine hydrochloride is widely used to treat seasonal allergies (allergic rhinitis), perennial allergic rhinitis, and chronic urticaria (urticaria). For patients with these conditions, cetirizine can relieve symptoms such as sneezing, runny nose, and itchy eyes. It is also used to treat insect bites and other minor allergic reactions.

Cetirizine is available in a variety of forms, including tablets, chewable tablets, and syrups, which provide flexible dosing options. It is suitable for adults and children over the age of two, making it a versatile option for treating allergies in different age groups.

References

1990. Cetirizine: Antiallergic therapy beyond traditional H1 antihistamines. The Journal of allergy and clinical immunology, 86(6).
DOI: 10.1016/s0091-6749(05)80251-9

1990. Urticaria: Clinical efficacy of cetirizine in comparison with hydroxyzine and placebo. The Journal of allergy and clinical immunology, 86(6).
DOI: 10.1016/s0091-6749(05)80246-5

1990. Prophylactic treatment of grass pollen‐induced asthma with cetirizine. Clinical and experimental allergy : journal of the British Society for Allergy and Clinical Immunology, 20(5).
DOI: 10.1111/j.1365-2222.1990.tb03140.x