Antiemetics

Question 1

Ondansetron: Class

Answer 1

5-HT3 receptor antagonist

Question 2

Ondansetron: use

Answer 2

PONV
Chemotherapy related N/V
Carcinoid Syndrome

Question 3

Ondansetron: Mechanism of Action

Answer 3

Inhibits serotonin both peripherally on vagus nerve terminals and centrally in the medulla’s Chemoreceptor trigger zone (CRTZ)

Question 4

Ondansetron: Dose

Answer 4

4 - 8 mg

Question 5

Ondansetron: Pharmacokinetics

Answer 5

Absorption: IV, PO

Onset: 10 minutes
Duration of Action: 4 hours

Metabolism: Hepatic

Elimination: Renal

Question 6

Ondansetron: Contraindications

Answer 6

Prolonged QT interval
Hypersensitivity

Question 7

Ondansetron: Considerations

Answer 7

Can cause Headache
prolongs QT interval

Question 8

Dexamethasone: Class

Answer 8

Synthetic glucocorticoid steriod

Question 9

Dexamethasone: Use

Answer 9

Decrease PONV risk
Reduce edema
Reduce postoperative pain

Question 10

Dexamethason: Mechanism of Action

Answer 10

↓ inflammation by inhibiting prostaglandin synthesis (from Vargo)

Dexamethasone’s mechanism of antiemetic activity is not entirely known, however:
↓ prostaglandin synthesis = ↓ N+V

decreases inflammation by suppression of migration of polymorphonuclear leukocytes and reversal of increased capillary permeability

inhibits phospholipase that is necessary for the conversion of phospholipids to arachidonic acid, which leads to the inflammatory chain reaction along both the cyclooxygenase and lipoxygenase pathways =↓ painq

Question 11

Dexamethasone: Dose

Answer 11

4 - 12 mg

Question 12

Dexamethasone: Pharmacokinetics

Answer 12

Absorption: IV, PO

Onset: 30 minutes
Duration of action: 36 hours

Metabolism: Hepatic

Elimination: Renal

Question 13

Dexamethasone: Contraindications

Answer 13

Systemic fungal infections
Live virus vaccines
Allergy/hypersensitivity

Question 14

Dexamethasone: Considerations

Answer 14

Delayed wound healing
HPA axis surpression
Hyperglycemia
Perianal itching (why it’s given after induction)