Ondansetron

Question 1

Brand Names

Answer 1

Zofran

Question 2

Broad Category

Answer 2

Antiemetic

Question 3

Pharmacological class

Answer 3

selective 5-HT3 receptor antagonist

Question 4

MOA

Answer 4

Selectively blocks serotonin 5-HT3 receptors (ligand gated ion channel), with little to no effect on dopamine receptors
- located in CTZ area postrema and the nucleus tactus solitarius
- also located peripherally on abdominal vagal afferents in the GI tract

Blocks emetogenic stimuli arising from the GI tract

Question 5

Indications / Clinical uses

Answer 5

Perioperative use
- rescue treatment and prophylaxis for PONV

Rescue and prophylaxis for chemo-induced N/V

Question 6

Adult dosing

Answer 6

4 mg IV

Question 7

Pediatric Dosing

Answer 7

50-100 mcg/kg (MAX 4 mg)

Question 8

Optimal timing?

Answer 8

End of surgery/procedure
Long procedure: 20-30 mins before end

Question 9

Onset

Answer 9

˜10 mins

Question 10

Duration

Answer 10

4-6 hours

Question 11

Most Common SE

Answer 11

HA and Diarrhea

Question 12

CV effects

Answer 12

QT prolongation (massive doses)
- black box warning: torasades de pointes (after doses of 32 mg given lol)

Question 13

Precautions

Answer 13

Hepatic impairment
- Prolongs clearance
CYP2D6 poor metabolizers (prolongs)
QT prolongation (cautious - leads to torsades)

Question 14

Drug to drug interactions

Answer 14

May precipitate serotonin syndrome when given with 2 or more other serotonergic meds
- SSRIs
- MAOIs
- fentanyl
- meperidine
- linezolid

Question 15

Metabolism

Answer 15

Hepatic CYP450
- CYP3A4
- CYP2D6
- CYP1A2

Conjugation

Question 16

Elimination

Answer 16

Primarily: Renal and Biliary

Question 17

Vd considerations

Answer 17

Moderate - Large
- extensive tissue distribution
- moderate lipophilicity

Question 18

Clearance Considerations

Answer 18

Reduced Clearance with severe hepatic impairment

Question 19

Protein binding

Answer 19

70-76%