A nurse is caring for a client who is prescribed aluminum hydroxide (Amphojel) and cimetidine (Tagamet HB). Which of the following statements from the client requires additional teaching?

A. Ondansetron agonizes serotonin receptors on afferent vagal neurons. – This is incorrect. Ondansetron works by blocking, not activating, serotonin (5-HT3) receptors in areas involved in nausea and vomiting.

B. Ondansetron agonizes serotonin receptors in the medulla oblongata. – This is incorrect. Ondansetron does not act as an agonist at serotonin receptors in the medulla oblongata; instead, it antagonizes receptors to reduce nausea.

C. Ondansetron agonizes dopaminergic receptors in the vestibular apparatus. – This is incorrect. Ondansetron does not affect dopaminergic receptors or the vestibular apparatus. Medications like promethazine address dopaminergic pathways.

D. Ondansetron blocks serotonin receptors in the chemoreceptor trigger zone. – This is correct. Ondansetron acts as a 5-HT3 receptor antagonist, blocking serotonin receptors in the chemoreceptor trigger zone and vagal nerve terminals, effectively preventing nausea and vomiting.

A. "This medication may cause increased libido." This is incorrect. Cimetidine (Tagamet) can cause side effects such as decreased libido, especially in men. This occurs because the drug inhibits the action of certain hormones, leading to sexual dysfunction.

B. "You may take this medication with antacids to prevent stomach upset." This is incorrect. Cimetidine should not be taken with antacids because antacids can reduce its absorption and effectiveness. It is advised to space the administration of cimetidine and antacids by at least 1 hour.

C. "This medication will neutralize your stomach acid." This is incorrect. Cimetidine works by blocking histamine receptors (H2 receptors), which reduces the production of stomach acid but does not neutralize it.

D. "This medication may cause decreased libido." This is correct. One of the side effects of cimetidine is reduced libido, particularly in male clients, due to its anti-androgenic effects.