A client who suffers from severe persistent allergic asthma is prescribed omalizumab (Xolair). Which statement below correctly describes the mechanism of action associated with omalizumab (Xolair)?

A. This medication (Benadryl) targets H2 receptors to alleviate symptoms: This statement is incorrect. Diphenhydramine is an H1 receptor antagonist, not an H2 antagonist. H1 receptors are primarily involved in allergic reactions, whereas H2 receptors are related to gastric acid secretion.

B. Take this medication on an empty stomach before breakfast. Drowsiness is a common side effect of diphenhydramine (Benadryl): While drowsiness is indeed a common side effect, taking diphenhydramine on an empty stomach is not necessarily required and may lead to gastrointestinal discomfort. It can be taken with food if preferred.

C. Avoid CNS depressants while taking diphenhydramine (Benadryl): This is an important teaching point. Diphenhydramine can cause sedation, and the use of other CNS depressants (like alcohol or sedatives) can enhance this effect, increasing the risk of excessive drowsiness or other complications.

D. This medication is a 2nd generation antihistamine: This statement is incorrect. Diphenhydramine is actually a first-generation antihistamine. First-generation antihistamines tend to cause more sedation and other side effects compared to second-generation antihistamines, which are less sedating.

E. Paradoxical reactions can be seen with this medication: This is true. In some individuals, particularly children, diphenhydramine can cause paradoxical reactions, such as increased excitability or hyperactivity, rather than the expected sedation. This is an important consideration to discuss with clients.

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.