A client diagnosed with allergic rhinitis is prescribed an antihistamine to assist with symptoms. Which of the following medications below would be considered a second-generation antihistamine?
cetirizine (Zyrtec)
chlorpheniramine (Aller-Chlor)
diphenhydramine (Benadryl)
montelukast (Singulair)
The Correct Answer is A
A) Cetirizine (Zyrtec): This medication is classified as a second-generation antihistamine. Second-generation antihistamines are designed to be less sedating than first-generation agents, as they are less likely to cross the blood-brain barrier. Cetirizine effectively alleviates symptoms of allergic rhinitis by blocking histamine receptors and is commonly used due to its efficacy and reduced sedation compared to older antihistamines.
B) Chlorpheniramine (Aller-Chlor): Chlorpheniramine is a first-generation antihistamine. It tends to cause more sedation and has a higher likelihood of causing side effects such as drowsiness, dry mouth, and dizziness. First-generation antihistamines are typically less selective and can affect the central nervous system more significantly than their second-generation counterparts.
C) Diphenhydramine (Benadryl): This medication is also a first-generation antihistamine. It is well-known for its sedative effects and is often used for allergic reactions, as well as for its sleep-inducing properties. Like other first-generation antihistamines, diphenhydramine can cause significant drowsiness and other anticholinergic effects.
D) Montelukast (Singulair): Montelukast is not an antihistamine but rather a leukotriene receptor antagonist. It is used for the management of allergic rhinitis and asthma but works through a different mechanism by blocking leukotriene receptors, thereby reducing inflammation and mucus production. It is not classified as an antihistamine, either first or second generation.
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Correct Answer is D
Explanation
A. Stimulate alpha-adrenergic receptors, thus producing vascular constriction of capillaries in nasal mucosa: This describes the action of decongestants, not guaifenesin. Guaifenesin does not work by constricting blood vessels; rather, its primary function is to help manage mucus production.
B. Compete with histamine for receptor sites, thus preventing a histamine response and overall congestion: This mechanism is associated with antihistamines, which are used to relieve symptoms of allergic reactions, not with guaifenesin. Guaifenesin does not block histamine but focuses on mucus management.
C. Treat allergic rhinitis and prevent motion sickness: While these are common uses for antihistamines, they do not apply to guaifenesin. Guaifenesin is primarily an expectorant and is not indicated for treating allergic rhinitis or motion sickness.
D. Loosen bronchial secretion to assist in elimination: Guaifenesin acts as an expectorant, promoting the clearance of mucus from the airways by loosening bronchial secretions. This facilitates easier expectoration of mucus, helping to relieve chest congestion associated with upper respiratory infections.
Correct Answer is C
Explanation
A. Inhibits the production of leukotrienes and histamine, preventing further asthma attacks: This statement is misleading. Omalizumab does not directly inhibit the production of leukotrienes or histamine; rather, it works by targeting IgE, which is involved in the allergic response.
B. Inhibits mast cells from releasing histamine, preventing further asthma attacks: While omalizumab does reduce the overall allergic response, it does so by binding to IgE rather than directly inhibiting mast cell activity. Therefore, this description does not accurately represent its primary mechanism of action.
C. Selectively binds to IgE, reducing allergic mediators and asthma attacks: This statement correctly describes the mechanism of action of omalizumab. By binding to immunoglobulin E (IgE), omalizumab prevents IgE from attaching to mast cells and basophils, thus reducing the release of allergic mediators that contribute to asthma attacks.
D. Stimulates alpha-adrenergic receptors to assist in reduction of allergic-related symptoms: This statement is incorrect. Omalizumab does not stimulate alpha-adrenergic receptors; such action is associated with certain bronchodilators. Omalizumab specifically targets IgE to mitigate allergic responses.