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 , steady-state volume of distribution and plasma clearance are 22 h, l/kg and l/h/kg respectively (based on intravenous and oral administration data). Azelastine is oxidatively metabolized by the cytochrome P450 family into its active metabolite, desmethylazelastine, and two inactive carboxylic acid metabolites. Approximately 75% of an oral dose is excreted in feces. Pharmacokinetics of orally administered azelastine are not affected by age, gender or hepatic impairment. 
During the post approval use of ASTEPRO % and ASTEPRO %, the following adverse reactions have been identified. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. Adverse reactions reported include: abdominal pain, atrial fibrillation , blurred vision, chest pain, confusion, disturbance or loss of sense of smell and/or taste, dizziness, dyspnea , facial swelling, hypertension , involuntary muscle contractions, nasal burning, nausea, nervousness, palpitations , paresthesia , parosmia, pruritus , rash, sneezing, insomnia, sweet taste, tachycardia , and throat irritation.
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