Antiemetics Dosages

Question 1

Ondansetron alternate name:

Answer 1

Zofran

Question 2

Ondansetron Structure:

Answer 2

5-HT3 Receptor Antagonist

Question 3

Ondansetron MOA:

Answer 3

1. Posses specific 5-HT3 subtype receptor antagonism without altering DA, Histamine, adrenergic or cholinergic receptor activity
2. 5-HT3 receptors are excitatory ligand gated Na and K channels found centrally and peripherally

Question 4

Ondansetron Onset:

Answer 4

Rapid

Question 5

Ondansetron duration of action:

Answer 5

4-8 hr

Question 6

Ondansetron PB:

Answer 6

75%

Question 7

Ondansetron Metabolism:

Answer 7

Hepatic CYP3A4 & 2D6, metabolites renally excreted

Question 8

Ondansetron IV dose:

Answer 8

4-8 mg

Question 9

Ondansetron IV peds dose:

Answer 9

0.15 mg/kg

Question 10

Ondansetron Side effects:

Answer 10

1. Headache
2. Diarrhea
3. QT prolongation
4. Cardiac arrhythmias
5. GI cramping

Question 11

Ondansetron Contraindications / cautions:

Answer 11

1. Avoid in prolonged QTc patients
2. Often given at end of case
3. Med allergy
4. Useful for PONV and CINV
5. Not effective for N/V from vestibular stimulation

Question 12

Granisetron alternate name:

Answer 12

Sustol

Question 13

Granisetron structure:

Answer 13

5-HT# receptor antagonist

Question 14

Granisetron MOA:

Answer 14

Blocks serotonin receptors in the CNS and GI prevents nausea and vomiting

Question 15

Granisetron Onset:

Answer 15

5-10 min

Question 16

Granisetron duration of action:

Answer 16

24 hr

Question 17

Granisetron PB:

Answer 17

75%

Question 18

Granisetron Metabolism:

Answer 18

CYP3A4, excreted 38% feces, 60% urine

Question 19

Granisetron IV dose:

Answer 19

1 mg

Question 20

Granisetron IV Peds dose:

Answer 20

10 mcg/kg

Question 21

Granisetron side effects:

Answer 21

1. Headache
2. Constipation
3. Dizziness
4. Fatigue
5. Sedation

Question 22

Granisetron Contraindications / cautions:

Answer 22

1. QT prolongation
2. Previous allergic
3. Contraindicated in patients taking serotonergic agents
4. Contraindicated in liver patients
5. Avoid in low magnesium

Question 23

Metoclopramide alternate name:

Answer 23

Reglan

Question 24

Metoclopramide structure:

Answer 24

Benzamide
Dopamine receptor antagonist

Question 25

Metoclopramide MOA:

Answer 25

1. Effective for PONV due to the antidopaminergic properties as well as cholinergic properties that stimulate the GI tract
2. Dopamine (D2) receptors found in CRTZ and vomiting center and modulate sensation of nausea in the CRTZ (contracts the lower esophageal sphincter and gastric fundus, increased gastric and small intestinal motility, reducing reflux and stomach contents)

Question 26

Metoclopramide Onset:

Answer 26

1-2 min

Question 27

Metoclopramide duration of action:

Answer 27

1-2 hr

Question 28

Metoclopramide PB:

Answer 28

30%

Question 29

Metoclopramide Metabolism:

Answer 29

CYP2D6

Question 30

Metoclopramide IV dose:

Answer 30

10 mg

Question 31

Metoclopramide side effects:

Answer 31

1. Fatigue
2. Restlessness
3. Extrapyramidal reactions
4. Drowsiness
5. Dizziness

Question 32

Metoclopramide contraindications / cautions:

Answer 32

1. Often given at the end of surgery
2. Parkinson’s disease contraindication
3. Restless leg syndrome contraindication
4. Bowel obstruction contraindication
5. Black box warning for tardive dyskinesia (>12 weeks duration)

Question 33

Droperidol alternate name:

Answer 33

Inapsine

Question 34

Droperidol structure:

Answer 34

Butyrophenone

Question 35

Droperidol MOA:

Answer 35

DA antagonist on the D2 receptor I the CTZ of brainstem, some alpha-adrenergic antagonism

Question 36

Droperidol Onset:

Answer 36

3-10 min

Question 37

Droperidol Duration of action:

Answer 37

2-4 hr

Question 38

Droperidol PB:

Answer 38

90%

Question 39

Droperidol Metabolism:

Answer 39

Hepatic CYP3A4 & CYP1A2 - undergoes hydroxylation and glucuronidation and excreted by the urine

Question 40

Droperidol IV / IM dose:

Answer 40

~ 0.625 to 1.25 mg (5 min before termination of anesthesia)
~ Max dose 2.5 mg slow push
~ Additional 1.25 mg doses may be given to achieve desired effect

Question 41

Droperidol side effects:

Answer 41

1. Fatigue
2. Restlessness
3. Extrapyramidal reactions
4. Drowsiness
5. Dizziness

Question 42

Droperidol contraindications / cautions:

Answer 42

1. Avoid in patients with prolong QT
2. Be careful with patients with history of NMS since its a DA antagonist
3. Patients with Parkinson’s - DA antagonist
4. Avoid in patients with heart failure - alpha adrenergic blocking affects - hypotension
5. Electrolyte imbalances - torsades risk

Question 43

Aprepitant alternate name:

Answer 43

Aponvie

Question 44

Aprepitant structure:

Answer 44

Neurokinin-1 (NK1) receptor antagonist

Question 45

Aprepitant MOA:

Answer 45

1. Selectively binds to and blocks NK1 receptors in the brain.
2. Substance P, a neurotransmitter, typically binds to NK1 receptors, triggering vomiting signals. By blocking these receptors, aprepitant prevents substance P from exerting its effect, thus reducing nausea and vomiting.

Question 46

Aprepitant Onset:

Answer 46

1-3 hr

Question 47

Aprepitant duration of action:

Answer 47

24 hr

Question 48

Aprepitant PB:

Answer 48

95%

Question 49

Aprepitant Metabolism:

Answer 49

CYP3A4, less by CYP1A2 and CYP2C19

Question 50

Aprepitant PO dose (PONV):

Answer 50

40 mg 3 hours before induction

Question 51

Aprepitant side effects:

Answer 51

1. Fatigue
2. Headache
3. Diarrhea
4. Hiccups
5. Cough

Question 52

Aprepitant Contraindications / cautions:

Answer 52

1. Penetrates BBB
2. Can cause Neutropenia
3. Not associated with prolonged QT
4. Only FDA approved NK1 receptor antagonist
5. Avoid if allergy