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A nurse is caring for a patient who has been newly prescribed ondansetron (Zofran) for post-operative nausea. What is the mechanism of action for ondansetron?

A.

Ondansetron agonizes serotonin receptors on afferent vagal neurons.

B.

Ondansetron agonizes serotonin receptors in the medulla oblongata.

C.

Ondansetron agonizes dopaminergic receptors in the vestibular apparatus.

D.

Ondansetron blocks serotonin receptors in the chemoreceptor trigger zone.

Answer and Explanation

The Correct Answer is D

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.


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Correct Answer is {"dropdown-group-1":"A","dropdown-group-2":"C"}

Explanation

  • Lispro (Humalog): This is a rapid-acting insulin with an onset of action of 15 to 30 minutes, making it effective for controlling blood sugar spikes after meals.
  • Glargine: This is a long-acting insulin that provides a steady level of insulin over 24 hours, helping to maintain baseline blood glucose levels.

Correct Answer is A

Explanation

A. "I will take both aluminum hydroxide (Amphojel) and cimetidine (Tagamet HB) at the same time." – This is correct. Taking aluminum hydroxide and cimetidine simultaneously reduces the effectiveness of cimetidine by impairing its absorption. This statement indicates a need for further teaching.

B. "I will take aluminum hydroxide (Amphojel) 1 hour before taking cimetidine (Tagamet HB)." – This is incorrect. Taking aluminum hydroxide 1 hour before cimetidine allows enough time for the antacid's effects on stomach acidity to stabilize, reducing interference.

C. "I can take aluminum hydroxide (Amphojel) 2 hours before taking cimetidine (Tagamet HB)." – This is incorrect. Taking the antacid 2 hours before cimetidine provides sufficient time for proper absorption of the medication.

D. None of the above – This is incorrect because statement A reflects improper administration.

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