Pharmacology - Antiemetics

Question 1

What are the 5 Antiemetics ?

Answer 1

• H1 antihistamine
• Antimuscarinics
• 5-HT3 receptor antagonist
• Dopamine antagonist
• NK1 receptor antagonist

Question 2

What is the most commonly used antihistamine?

Name 1.

What is a side effect of it ?

Answer 2

H1 antihistamine

Cyclizine

Can cause sedation

Question 3

What type of medication is Hyosine ?

When is it used ?

What is a side effect ?

Answer 3

Its an Antimuscarinic

Used for motion sickness

Can casue dry mouth and blurred vision.

Question 4

Name a 5-HT3 receptor antagonist.

What’s its mechanism of action?

When is it used?

Name a side effect.

Answer 4

• Ondansetron

-Dual location of effect in vagal afferents and chemoreceptor trigger zone ( located in the medulla oblongata)

• Used commonly in chemotherapy and after surgery! its effective for all types of surgery.

Can cause constipation !!!!

Question 5

Name a dopamine antagonist.

When is it used ?

Which one can be used in pregnancy ?

Which has poor penetration of BBB?

Answer 5

Metoclopramide, domperidone.

2nd line for mild emesis.

Metoclopramide can be used in pregnancy.

Domperidone fewer CNS adverse effects as poor penetration of BBB, but effectiveness queried

Question 6

What steroid can be used in moderate emesis ?

Answer 6

Dexamethasone

Question 7

What would you use for mild emesis ?

Answer 7

Mild emesis: H1 antihistamines, DA receptor antagonists

Question 8

What can you use for moderate emesis ?

Answer 8

• Moderate (chemotherapy) – severe: dexamethasone (with chemotherapy), 5-HT3 antagonists, NK1 antagonists,

Question 9

What can be used for motion sickness ?

Answer 9

• Motion sickness: hyoscine, H1 antihistamines

Question 10

What can be used for pregnacy ?

Answer 10

• Pregnancy (only if severe): metoclopramide, promethazine

Question 11

What cells sense the environment and release mediators such as 5-HT to trigger the vagus nerve to stimulate emesis?

Answer 11

ECL cells