Anti-emetics

Question 1

What are the general indications for anti-emetics?

Answer 1

Nausea and vomiting

Question 2

What are the types of anti-emetics?

Answer 2

• H1 receptor antagonists
• 5-HT3 receptor antagonists
• D2 receptor antagonists
• Phenothiazines
• Hyoscine (anti-muscarinic)

Question 3

What are some examples of H1 receptor antagonists?

Answer 3

• Cyclizine

- Promethiazine

Question 4

How do H1 receptor antagonists act as anti-emetics?

Answer 4

Block histamine (H1) and acetylcholine receptors in the chemoreceptor trigger zone

Question 5

What are some examples of 5-HT3 receptor antagonists?

Answer 5

Ondansetron

Question 6

How does ondansetron exert its anti-emetic effects?

Answer 6

Unknown

Question 7

What are some examples of D2 receptor antagonists?

Answer 7

• Metoclopramide

- Domperidone

Question 8

How do D2 receptor antagonists act as anti-emetics?

Answer 8

Inhibit dopaminergic stimulation on the chemoreceptor trigger zone

Question 9

What are some examples of phenothiazines?

Answer 9

• Prochlorperazine

- Chlorpromazine

Question 10

How do phenothiazines act as anti-emetics?

Answer 10

Block a variety of receptors that stimulate the chemoreceptor trigger zone

Question 11

How does hyoscine act as an anti-emetic?

Answer 11

Exerts a spasmolytic action on the smooth muscle of the gastrointestinal biliary and genitourinary tracts and has a peripheral anticholinergic effect on the visceral wall

Question 12

What anti-emetic is best for drug-induced vomiting?

Answer 12

Cyclizine

Question 13

What anti-emetic is best for vomiting in pregnancy?

Answer 13

Promethiazine

Question 14

What anti-emetic is best post-operatively?

Answer 14

Hyoscine

Question 15

What anti-emetic is used for obstruction?

Answer 15

Metoclopramide

Question 16

What anti-emetic is best for motion sickness?

Answer 16

Hyoscine

Question 17

How can anti-emetics be administered?

Answer 17

• PO
• IV
• IM
• PR

Question 18

When should phenothiazines and dopamine receptor antagonists be avoided?

Answer 18

In Parkinson’s disease

Because of increased risk of extra-pyramidal side effects

Question 19

When is domperidone contraindicated?

Answer 19

• In people with underlying cardiac or hepatic impairment
• In people on medications that inhibit CYP3A4

Due to cardiac side effects

Question 20

What caution should be taken with metoclopramide?

Answer 20

Only use for up to 5 days

Question 21

Why should metoclopramide only be used for up to 5 days?

Answer 21

It is associated with severe neurological adverse effects

Question 22

What monitoring may be required for patients on 5HTs antagonists or phenothiazines?

Answer 22

ECG to look for prolonged QT

Question 23

Can anti-emetics be used in combination?

Answer 23

Should be avoided

Question 24

Which anti-emetics should metoclopramide not be prescribed alongside?

Answer 24

• Ondansetron

- Cyclizine

Question 25

What anti-emetics should cyclizine not be prescribed alongside?

Answer 25

- Metoclopramide | - Domperidone

Question 26

What medications can cyclizine interact with?

Answer 26

- Opioids (increases sedation) | - Anticholinergics

Question 27

What medications does ondansetron interact with?

Answer 27

- SSRI's | - Enhanced action when prescribed with steroids

Question 28

What medications does metoclopramide interact with?

Answer 28

- Effect is reduced by opioids

Question 29

What drugs can domperidone interact with?

Answer 29

Absorption can be reduced by antacids and H2 receptor antagonists

Question 30

What drugs does hyoscine interact with?

Answer 30

This is in the muscarinic antagonist cards

Question 31

What are the important side-effects of H1 receptor antagonists?

Answer 31

Drowsiness

Question 32

What are the important side-effects of phenothiazines?

Answer 32

- Drowsiness - Postural hypotension - Prolonged QT interval

Question 33

What are the important side-effects of muscarinic antagonists?

Answer 33

- Postural hypotension | - Dry mouth

Question 34

What are the important side-effects of 5-HT3 receptor antagonists?

Answer 34

Prolonged QT interval

Question 35

What are the important side-effects of D2 receptor antagonists?

Answer 35

Extrapyramidal side-effects

Question 36

What anti-emetics can cause headache, constipation/diarrhoea?

Answer 36

Several types

Question 37

What patient counselling should be given to patients on anti-emetics?

Answer 37

- Indication - Side-effects and consequences - Anti-emetic can be changed if no relief

Question 38

What are the most important side-effects to warn patients about with anti-emetics?

Answer 38

- Postural hypotension - Dizziness - Extrapyramidal side-effects

Question 39

What can be the consequences of anti-emetics causing dizziness and postural hypotension?

Answer 39

- Falls - Unable to drive - Unable to operate machinery

Question 40

What are some extrapyramidal side-effects caused by D2 receptor antagonists?

Answer 40

- Tremor - Bradykinesia - Acute dystonia - Akathasia - Tardive dyskinesia - Parkinsonism

Question 41

What patient counselling is required with anti-emetics?

Answer 41

- Indication and side effects - Impairment of function - Extrapyramidal side effects - Changing anti-emetic if no relief