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?

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.