The Nurse Is Reviewing the Mechanisms of Action for Ondansetron

The nurse is reviewing the mechanisms of action for ondansetron (Zofran) being used to treat nausea for a person receiving chemotherapy for cancer. Which of the following accurately reflects the mechanism of action of ondansetron?

A) Ondansetron is a serotonin receptor antagonist which blocks the effect of serotonin on vagal afferent nerves that stimulate the vomiting centre.
B) Ondansetron blocks dopamine receptors in the chemoreceptor trigger zone to suppress nausea and vomiting.
C) Ondansetron acts by blocking histamine and acetylcholine receptors in the neural pathway from the inner ear to the vomiting centre.
D) Ondansetron antagonizes H1-receptors, competing for binding with free histamine, thus relieving nausea and vomiting.