Antiemetic Drugs

Question 1

1) Vomiting AKA?
2) Complex reflex activated by what?
3) What stimulates the activation?

Answer 1

1) Emesis
2) Vomiting Center
3) Chemoreceptor Trigger Zone (CTZ)
(& cerebral cortex + inner ear)

Question 2

Emesis is caused by the “em’s” (M’s):

1) Medications? (4)

Answer 2

1) Medications:
- Chemo Cancer
- Opioids
- General anaesthetics
* ** DIGOXIN

Question 3

Antiemetic Drugs:

1) What do they do?
2) Most effective when given when?
3) What determines choice of antiemetic drug?

Answer 3

1) Suppress Nausea & Vomiting
2) Prophylactically (preventative)
(instead of after symptoms occur)
3) Clinical situation & likelihood of Adverse Effects

Question 4

Classification of antiemetics:

What are the types of antiemetics? (7)

Answer 4

Receptor antagonists:

1) Serotonin (5HT3)
2) Dopamine antagonists (Antipsychotics)
3) Antihistamines
4) Anticholinergics (Muscarinic ACh antagonists)
5) Supstance P/Neruokinin NK1
6) Glucocorticoids
7) Cannabinoids

Question 5

1) What type of antiemetic drug is the most effective for CINV (Chemotherapy-Induced Nausea & Vomiting)?

Answer 5

1) Serotonin (5HT3) Antagonists

Question 6

Serotonin 5HT3 Antagonists:

1) Action?
2) Use? (3)
3) Adverse effects?
4) When is it given?
5) Drugs? (the part of name that all the generic names have in common?

Answer 6

1) Blocks serotonin receptors on vagal visceral afferents in GIT & CTZ
2) - Cytotoxic drug-induced vomiting
- Raidiation-induced vomiting
- Prevents post-op nausea & vomiting
3) Well tolerated with minor side-effects
(headache, flushing, constipation or diarrhoea, abdominal discomfort
and rash on iv injection)
4) ONLY given during first 24 hrs of cytotoxic drug treatment
5) ‘setron’
(ondansetron, dolasetron, granisetron, tropisetron)

Question 7

Dopamine Antagonists (Antipsychotics):

1) Name 3 drugs (generic + brand)
2) Action?
3) Use?
4) Adverse effects?

Answer 7

1) Metoclopramide (MAXALON)
Domperidone
Prochlorperazine (STEMETIL)
2) Blocks dopamine receptors in CTZ
3) More severe Nausea/Vomiting:
- Drug induced
- Disease induced
- Malignancy associated
4) - Significant sedation
- Acute muscle dystonia
- Extrapyramidal effects (parkinsonism)

Question 8

Metoclopramide (MAXALON):

1) What receptors does it act on?

Answer 8

1) D2, 5HT3 & 5HT4 receptors

Question 9

Domperidone:

1) Action?
2) Use?
3) Adverse effects?

Answer 9

1) Blocks action of dopamine.
D2 & D3 receptors in CTZ.
2) Low antiemetic actions. 
Used together with Metoclopramide, cyclizine, & 5HT3 receptor antagonists (GraniSETRON)
3) - Rare extrapyramidal effects
- Hyperprolactinemia can occur

Question 10

Anticholinergics: (Muscarinic) Antagonists:

1) Action?
2) Use?
3) Adverse effects?
4) Drug? (Main)
5) Route of administration?

Answer 10

1) Block cholinergic link from Vestibular Apparatus (balance system) to Vomiting Center
2) Motion Sickness
3) - Dry mouth
- blurred vision
- sedation (less than antihistamines)
4) Hyoscine (Scopolamine)
5) Oral or Transdermal patch

Question 11

Antihistamines:

1) Action?
2) Use?
3) Adverse effects?
4) Drugs? (2)
5) When given? & How long lasts?

Answer 11

1) Blocks acetylcholine in Vestibular Apparatus (balance system) 
& Histamine H1 receptors in nucleus of solitary tract (brain)
2) - Motion Sickness
- Morning Sickness
3) - Sedation
- Impair vigilant performance
4) Dimenhydrinate OR Promethazine
5) 1/2 - 1 hr Before journey
Lasts 4-6 hrs

Question 12

Neurokinin Antagonists: SUBSTANCE P

1) Modulator of what? (4)

Answer 12

• Nociception (sense of pain)
• Stress
• Anxiety
• Nausea/Vomiting

Question 13

Aprepitant (EMEND):

1) Action?
2) Use?
3) How is it used?

Answer 13

1) Antagonist of substance P at Neurokinin 1 (NK1)
2) Prevention of Acute & Delayed Nausea/Vomiting cancer Chemotherapy
3) ONLY in combination with other Antiemetics

Question 14

Dexamethasone:

1) Action?
2) Use?
3) Adverse effects?

Answer 14

1) Inhibit Serotonin (5HT3) receptors at Clinical Concentrations
2) Suppress Nausea/Vomiting
(SHORT TERM & intermittent use only)
3) Only acute side effects:
- Flushing
- Perineal (between genitals & anus) itching

Question 15

Nausea & Vomiting in Pregnancy (NVP):

1) NVP AKA?
2) When does it occur?
3) How common is it?
4) Severity?

Answer 15

1) Morning sickness
2) First 3 months (can be very severe)
3) Nausea: 70-80% of pregnant women
Vomiting: 50%
4) 1% very severe: Needs hospitalisation for Dehydration & Electrolyte Imbalance

Question 16

Management of Nausea & Vomiting in Pregnancy (NVP):

1) Why is drug use in NVP problematic?
2) What is the only recommended drug?
3) Can also be treated with what?
4) Alternative drugs? (2)

Answer 16

1) Higher teratogenetic effect in first trimester
(interfere with normal embryonic development)
2) Doxylamine (H1 Antihistamine)
3) - Ginger
- PYRIDOXINE
4) Metoclopramide + Pyridoxine
OR (if unsuccessful)
Prochloperazine (stemetil) OR Promethazine (antihistamine)

Question 17

Treatment of Motion Sickness:

1) What is the most effective drug?
2) Another drug used?
3) When should drugs be given to be most effective?
4) Which drugs are ineffective for treatment of motion sickness?

Answer 17

1) Muscarinic antagonist (Anticholinergics):
SCOPOLAMINE (hyoscine)
2) Antihistamines:
Dimenhydrinate OR Promethazine
(Block pathway connecting inner ear to VC)
3) Prophylactically 1/2-1 hr Before
4) Dopamine antagonists e.g. metoclopramine

Question 18

Chemotherapy-Induced Nausea & Vomiting (CINV):

1) Severe Nausea/Vomiting leads to?

Answer 18

1) - Dehydration
- Electrolyte imbalances
- Nutrient depletion
- Eosophageal tears
* ** Discontinue Chemotherapy

Question 19

Chemotherapy-Induced Nausea & Vomiting (CINV):

3 types of emesis following cytotoxic chemotherapy?

Answer 19

1) Acute (Post treatment):
- Within 24 hrs of Chemo (stimulation of CTZ)
2) Delayed:
- Begins after 24 hrs; may last 120 hrs
3) Anticipatory:
- Associated with N/V from previous Chemo experience

Question 20

Principles in Management of Chemotherapy-Induced Nausea & Vomiting (CINV):

1) What is more effective to suppress CINV?
2) What is the preferred antiemetic regimen for patients receiving highly emetogenic drugs?

Answer 20

1) Combination of drugs > Monotherapy
2) Consists of 3 drugs:
Aprepitant + Glucocorticoid + Serotonin Antagonist

Question 21

Treatment Guidelines: CINV:

1) Minimal emetic risk?
2) Low risk of emesis?
3) Moderate risk of emesis?
4) High emetic risk?

Answer 21

1) Dexamethasone (followed by) Metoclopramide
2) Metoclopramine/Prochlorperazine
(with OR without) Dexamethasone
3) Serotonin(5HT3) Antagonist + Metoclopramide + Dexamethasone
4) As above + Aprepitant:
Serotonin(5HT3) Antagonist + Metoclopramide + Dexamethasone + Aprepitant