A client frequently takes diphenhydramine (Benadryl) to alleviate his upper respiratory symptoms associated with allergies. Which of the following mechanism of actions applies to diphenhydramine (Benadryl)?
stimulates effects of histamine by occupying all H receptor sites.
blocks effects of histamine by competing and occupying H1 receptor sites.
blocks effects of histamine by competing and occupying H2 receptor sites.
stimulates effects of histamine by increasing amount of H2 receptor sites.
The Correct Answer is B
A. Stimulates effects of histamine by occupying all H receptor sites: This statement inaccurately describes the action of diphenhydramine. Instead of stimulating histamine effects, diphenhydramine actually blocks them, particularly at H1 receptors, which are involved in allergic responses.
B. Blocks effects of histamine by competing and occupying H1 receptor sites: This accurately describes the mechanism of action of diphenhydramine. As an antihistamine, it competes with histamine for binding to H1 receptor sites, effectively reducing symptoms of allergies, such as sneezing, itching, and nasal congestion.
C. Blocks effects of histamine by competing and occupying H2 receptor sites: This option is incorrect because H2 receptor antagonists are used primarily to reduce gastric acid secretion, not to treat allergic reactions. Diphenhydramine specifically targets H1 receptors, not H2 receptors.
D. Stimulates effects of histamine by increasing the amount of H2 receptor sites: This statement is also incorrect. Diphenhydramine does not stimulate histamine activity or increase receptor sites. Instead, it functions to inhibit the action of histamine at H1 receptors, which is fundamental in alleviating allergy symptoms.
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Correct Answer is A
Explanation
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.
Correct Answer is A
Explanation
A. Use this inhaler 15 minutes prior to physical activity: This is the correct recommendation for cromolyn. It is a mast cell stabilizer that helps prevent asthma symptoms by inhibiting the release of inflammatory mediators. Using it before physical activity can help minimize exercise-induced bronchospasm.
B. Tachycardia is an adverse effect associated with this medication: This statement is misleading. Cromolyn is not typically associated with tachycardia as an adverse effect. Unlike bronchodilators, which can cause increased heart rate, cromolyn primarily works to stabilize mast cells and has a different side effect profile.
C. This medication should not be discontinued abruptly: While it is generally good practice to consult a healthcare provider before stopping any asthma medication, cromolyn does not have a significant risk of withdrawal symptoms like corticosteroids might. It is more important to maintain regular use for effectiveness rather than fear abrupt discontinuation.
D. Injections are required weekly to properly prevent asthma attacks: This statement is incorrect. Cromolyn is administered via inhalation, not by injection, and does not require weekly injections. Patients should use the inhaler as prescribed, typically several times a day, depending on their individual treatment plan.