Azelastine, sold under the brand name Astelin among others, is a H1 receptor-blocking medication primarily used as a nasal spray to treat allergic rhinitis (hay fever) and as eye drops for allergic conjunctivitis.[ Onset of effects is within minutes when used in the eyes and within an hour when used in the nose.][
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Common side effects include headache, sleepiness, change in taste, and sore throat.[ It is unclear if use is safe during pregnancy or breastfeeding.][
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Azelastine was patented in 1971 and came into medical use in 1986.
Medical uses
Azelastine nasal spray is indicated for the local treatment of the symptoms of seasonal allergic rhinitis and perennial allergic rhinitis, such as rhinorrhea, sneezing and nasal pruritus in people five years of age and older.
Side effects
Azelastine is safe and well tolerated in both adults and children with allergic rhinitis.
The most common side effect is a bitter taste (about 20% of people). Due to this, the manufacturer has produced another formulation of azelastine with sucralose.
In addition, anosmia (loss in the ability to smell) can occur with nasal spray antihistamines (including both formulations of azelastine).
Pharmacology
Pharmacodynamics
Azelastine has a triple mode of action:
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Antihistamine effect,
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Mast-cell stabilizing effect and
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Anti-inflammatory effect.
Pharmacokinetics
The systemic bioavailability of azelastine is approximately 40% when administered intranasally. Maximum plasma concentrations (Cmax) are observed within 2–3 hours. The elimination half life is 22 h, the steady-state volume of distribution is 14.5 L/kg, and the plasma clearance is 0.5 L/h/kg (based on intravenous and oral administration data). Approximately 75% of an oral dose is excreted in feces. Pharmacokinetics of orally administered azelastine is not affected by age, gender, or hepatic impairment.
Metabolism
Azelastine is oxidatively metabolized by the cytochrome P450 family into its active metabolite, desmethylazelastine, and two inactive carboxylic acid metabolites.
Chemical properties
The chemical nomenclature of azelastine is (±)-1-(2H)-phthalazinone, 4-(4-chlorophenyl)-2-(hexahydro-1-methyl-1H-azepin-4-yl)-monohydrochloride. It is white, almost odorless with a bitter taste.[drugs.com Azelastine Page accessed 28 June 2015]
History
Azelastine was first synthesized by Dietrich in 1971, developed through collaborative research between Eisai Co., Ltd. in Japan and Degussa GmbH in West Germany.
An ophthalmic drop formulation of azelastine (Optivar) was approved by the US FDA in 2000.
Research
Azelastine may have in vitro antiviral activity against respiratory viruses, including SARS-CoV-2.
