Azelastine hydrochloride
[CAS# 79307-93-0]

Identification

• Classification: API >> Antiallergic >> Antihistamine
• Name: Azelastine hydrochloride
• Synonyms: 4-[(4-Chlorophenyl)methyl]-2-(1-methylazepan-4-yl)-phthalazin-1-one hydrochloride
• Molecular Formula: C₂₂H₂₄ClN₃O.HCl
• Molecular Weight: 418.36
• CAS Registry Number: 79307-93-0
• EC Number: 620-469-0
• SMILES: CN1CCCC(CC1)N2C(=O)C3=CC=CC=C3C(=N2)CC4=CC=C(C=C4)Cl.Cl

Properties

• Solubility: 10 mM (DMSO)
• Melting point: 226 °C

Safety Data

• Hazard Symbols: GHS07;GHS08 Warning
• Risk Statements: H302-H361
• Safety Statements: P203-P264-P270-P280-P301+P317-P318-P330-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute toxicity	Acute Tox.	4	H302
Reproductive toxicity	Repr.	2	H361
Acute toxicity	Acute Tox.	4	H332
Chronic hazardous to the aquatic environment	Aquatic Chronic	2	H411
Self-heating substances or mixtures	Self-heat.	2	H252
Acute toxicity	Acute Tox.	4	H312
Skin irritation	Skin Irrit.	2	H315
Specific target organ toxicity - single exposure	STOT SE	3	H335
Flammable solids	Flam. Sol.	2	H228

Discovery and Applications

Azelastine hydrochloride is an antihistamine medication primarily used to treat allergic conditions such as allergic rhinitis (hay fever) and allergic conjunctivitis. Discovered and developed in the 1970s, azelastine has since become a widely prescribed drug due to its effectiveness in alleviating symptoms of allergy with a relatively low incidence of side effects.

Azelastine hydrochloride works by blocking histamine H1 receptors. Histamine is a chemical in the body that is released during allergic reactions, leading to symptoms such as sneezing, itching, runny nose, and watery eyes. By preventing histamine from binding to its receptors, azelastine reduces or prevents these allergic symptoms, providing relief to individuals suffering from allergies.

The discovery of azelastine was part of broader research efforts aimed at developing more effective and targeted antihistamines. Previous generations of antihistamines often caused significant drowsiness and other side effects, limiting their use. Azelastine was developed to offer a better balance between efficacy and tolerability, making it suitable for long-term use in managing chronic allergic conditions.

Azelastine hydrochloride is available in several formulations, including nasal sprays and eye drops. The nasal spray is commonly used to treat allergic rhinitis, offering quick relief from nasal symptoms such as congestion, sneezing, and itching. Eye drops containing azelastine are used to treat allergic conjunctivitis, alleviating symptoms like itchy, red, and watery eyes. The medication is typically administered twice daily, though the frequency can vary depending on the severity of symptoms and the specific formulation used.

One of the key advantages of azelastine hydrochloride is its rapid onset of action. Patients often experience symptom relief within minutes of administration, making it an effective option for managing acute allergic reactions. Additionally, azelastine is known for its relatively low sedative effect compared to earlier antihistamines, allowing patients to use it during the day without significant drowsiness.

The safety profile of azelastine is well-established, with common side effects generally mild and transient. These can include a bitter taste in the mouth, headache, and mild drowsiness, particularly when used as a nasal spray. Serious side effects are rare, making azelastine a preferred choice for many patients with allergic conditions.

Azelastine hydrochloride is also sometimes used off-label for other conditions, such as non-allergic rhinitis, where it helps reduce nasal symptoms caused by irritants other than allergens. Its versatility in treating different types of rhinitis highlights its broad applicability in clinical practice.

In conclusion, azelastine hydrochloride is a significant advancement in the treatment of allergic conditions, offering effective relief with a favorable safety profile. Its development has provided patients with a reliable option for managing both acute and chronic allergy symptoms, improving their quality of life.

References

2023. Efficacy and safety of the combination nasal spray olopatadine hydrochloride-mometasone furoate in the treatment of allergic rhinitis. Allergo Journal International, 13(1).
DOI: 10.1007/s40629-023-00282-5

2011. Efficacy and safety of azelastine 0.15% nasal spray administered once daily in patients with allergy to Texas mountain cedar pollen. International Forum of Allergy & Rhinology, 1(3).
DOI: 10.1002/alr.20065

2008. Comparison of the Conjunctival Toxicity of Topical Ocular Antiallergic Agents. Journal of ocular pharmacology and therapeutics : the official journal of the Association for Ocular Pharmacology and Therapeutics, 24(6).
DOI: 10.1089/jop.2008.0071