Respiratory system: rhinitis

23 Respiratory system


rhinitis





Questions



image What is allergic rhinitis?

image What drugs are used for the treatment of rhinitis?

Rhinitis is a common and debilitating disease characterized by rhinorrhoea, sneezing, itching nasal congestion and obstruction. Allergic rhinitis is a common form of this disease, and symptoms arise following acute exposure to allergen, which binds to cell surface-bound IgE on mast cells and triggers their degranulation and release of inflammatory mediators such as histamine, tryptase, cysteinyl-leukotrienes and cytokines. This acute response triggers symptoms of itching, sneezing, rhinorrhoea and nasal congestion (Fig. 3.23.1). A delayed recruitment of lymphocytes and eosinophils to the nasal mucosa, and the mediators released from these cells, is also thought to contribute towards these symptoms, although nasal congestion and obstruction predominate. Non-allergic rhinitis is not caused by an airborne allergen and symptoms might be triggered by viral infection, hormonal imbalance or vasomotor, occupational or drug causes. Allergy avoidance can minimize the symptoms of allergic rhinitis but this has many disadvantages as it requires a change in lifestyle, which is impracticable for many. There area number of pharmacological approaches for the treatment of allergic rhinitis (Fig. 3.23.1B).


image

Fig. 3.23.1 Allergic rhinitis. (A) Formation of inflammatory mediators; (B) reactions in the nasal passages.



Pharmacological treatments



Antihistamines


Antihistamines are the most frequently used drugs in the treatment of allergic rhinitis. Histamine released from mast cells acts on a number of cells within the nasal mucosa resulting in symptoms of itching, sneezing (sensory nerves), rhinorrhoea and mucus secretion (submucosal glands). These drugs are less effective in reducing nasal congestion. First-generation antihistamines such as diphenhydramine and chlorpheniramine cross the blood–brain barrier and cause drowsiness; the incidence of this side-effect was reduced with second-generation antihistamines terfenadine and astemizole; however, these drugs produced potentially fatal cardiac arrhythmias in some patients. Newer antihistamines such as loratidine and fexofenadine are non-sedating, non-cardiotoxic and have long duration of action. As such, these drugs are administered orally. Intranasal preparations are available and include azelastine, which provides rapid relief. Some antihistamines also have a mild anti-inflammatory action (e.g. cetirizine).

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Jul 18, 2016 | Posted by in PHARMACY | Comments Off on Respiratory system: rhinitis

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