PreOp Meds: 5HT3 Antagonists & Ondansetron (Zofran)

Question 1

Where is serotonin released from and how does it cause emesis?

Answer 1

• Released via chromaffin cells of small intestine → vagal stimulation via 5HT3 receptors

Question 2

Where are the highest concentration of serotonin receptors found?

Where else are they commonly found?

Answer 2

• Brain & GI tract
• Kidney, liver, lung, stomach

Question 3

What is the greatest general benefit of 5HT3 antagonists?
What are they not useful for?

Answer 3

• Very few side effects
• Not useful for motion sickness

Question 4

What is the E ½ time of Ondansetron? Why is this relevant?

Answer 4

• 4 hours: dose must be given so that effect peaks towards end of the case.

Question 5

What is the normal dose of Ondansetron?

Answer 5

• 4 - 8 mg IV

Question 6

If side effects are seen with ondansetron, what might be seen?

Answer 6

• Slight QT prolongation, headache, diarrhea