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What is Nasal spray and explain in detail?
Nasal sprays are used to deliver medications locally in the nasal cavities or systemically. They are used locally for conditions such as nasal congestion and allergic rhinitis. In some situations, the nasal delivery route is preferred for systemic therapy because it provides an agreeable alternative to injection or pills. Substances can be assimilated extremely quickly and directly through the nose. Many pharmaceutical drugs exist as nasal sprays for systemic administration (e.g. sedative-analgesics, treatments for migraine, osteoporosis and nausea). Other applications include hormone replacement therapy, treatment of Alzheimers disease and Parkinsons disease. Nasal sprays are seen as a more efficient way of transporting drugs with potential use in crossing the blood–brain barrier.

Antihistamines
Antihistamines work by competing for receptor sites to block the function of histamine, thereby reducing the inflammatory effect. Antihistamine nasal sprays include:

Azelastine hydrochloride
Levocabastine hydrochloride
Olopatadine hydrochloride

Corticosteroids
Corticosteroid nasal sprays can be used to relieve the symptoms of sinusitis, hay fever, allergic rhinitis and non-allergic (perennial) rhinitis. They can reduce inflammation and histamine production in the nasal passages, and have been shown to relieve nasal congestion, runny nose, itchy nose and sneezing. Side effects may include headaches, nausea and nose bleeds. Corticosteroid nasal sprays include:

Beclomethasone dipropionate
Budesonide
Ciclesonide
Flunisolide
Fluticasone furoate
Fluticasone propionate
Mometasone
Triamcinolone acetonide

Saline
Saline sprays are typically non medicated. A mist of saline solution containing sodium chloride is delivered to help moisturize dry or irritated nostrils. This is a form of nasal irrigation. They can also relieve nasal congestion and remove airborne irritants such as pollen and dust thereby providing sinus allergy relief.
Three types of nasal sprays preparations of sodium chloride are available including hypertonic (3% sodium chloride or sea water), isotonic (0.9% sodium chloride) and hypotonic (0.65% sodium chloride). Isotonic solutions have the same salt concentration as the human body, whereas hypertonic solutions have a higher salt content and hypotonic solutions have a lower salt content