Anti-Emetics

Question 1

What are the 3 stages of Emesis?

Answer 1

1. Feelings of nausea
2. Retching
3. Vomiting

Question 2

What is an Emetic?

Answer 2

It’s an agent that causes vomitting

Question 3

What is Emesis?

Answer 3

It’s a physical event of forceful evacuation of gastric content through the mouth.
It’s a protective mechanism in response to something harmful being digested or can occur in motion sickness and vestibular disorders.

Question 4

True or false…

The vomiting reflex is regulated by the CNS in the midbrain

Answer 4

FALSE!!!

The vomiting reflex is regulated by the CNS (MEDULLA)

It’s controlled and centralized within the brain stem in a neural network on the dorsal surface of the medulla.

Question 5

What are the 3 main imputs to the dorsal vagal complex which cause nausia and vomitting.

Answer 5

1. The chemoreceptor trigger zone (in the dorsal vagal complex) - Endogenous substances/ toxins/ drugs
2. The Vagal Pathway - sensory imput, stimuli from pharynx, stimuli from GI tract
3. The Vestibular Pathway - Disorientated motion

Question 6

Which part of the vomiting centre is effected by :

Disorientated motion

Answer 6

Vestibular Pathway

For example travel sickness

Question 7

Which part of the vomiting centre is effected by:

Sensory imput (smell, pain, sight, tough)

Answer 7

Vagal Pathway

Question 8

Which part of the vomiting centre is effected by:

Toxins/ Drugs and Endogenous substances?

Answer 8

The chomoreceptor trigger zone

Main sight of action for anti emetic drugs

Question 9

What part of the vomiting centre is the main site of action for antiemetic drugs?

Answer 9

The Chemoreceptor Trigger Zone

Question 10

Name some of the types of Endogenous mediators (neurotransmitters) for Emesis that attach to specific receptors .

(these receptors are targets from anti emetic drugs as it prevents the neurotransmitters from binding and causing emesis)

Answer 10

• seretonin (5HT3 receptor)
• ACh (M receptor)
• Dopamine (D2 receptor)
• Substance P (NK1 receptor)
• Histamine (H1 receptor)
• Enkephalin (delta recetor)

Question 11

Name some of the receptors that are targets for anti-emetics.

Anti-emetics bind to the receptors preventing neurotransmitters from binding and causing emesis.

Answer 11

• Histamine receptors_ H1
• Seretonin in 5HT3 receptors
• Muscarinic: M
• Dopamine D2
• Substance P/Neurokinin: Nk receptors

Question 12

Where is the location of most of the neurotransmitter receptors envolved in emesis?

Answer 12

THE VOMITING CENTRE (M , H1, 5HT3 , NK1 receptors)

There are also other zones where other receptors are:

• Chemoreceptor Triggering zone (5HT3, NK1, D2)
• Vestibular Pathway (M, H1)
• Vagal Pathway (5HT3)

Question 13

Name some H1 receptor antagonists and what they’re used for

Answer 13

CYCLAZINE - Motion Sickness
CINNARIZINE - Motion Sickness & Vestibular diseases
PROMETHAZINE - Severe morning sickness

SE- drousiness and sedation (zzzzz for sleepiness)

Question 14

Which of the following is NOT associated with emesis?

• The sympathetic pathway
• The chemoreceptor trigger zone (CTZ)
• The vestibular pathway
• The vagal pathway

Answer 14

The sympathetic pathway

Question 15

What is the drug ‘Promethazine’ used for?

Answer 15

It’s used for severe morning sickness. It’s a H1 receptor antagonist.

(P is for Pregnancy)

Question 16

What is the H3 receptor agonist drug

BETAHISTINE HYDROCLORIDE

used for?

Answer 16

It’s used as an antivertigo drug.

Activated the H receptors on blood vessles and inner ear causing vasodilation and permiability.

SE - GI disturbances, Rash, Pruritis, Headache

Question 17

True of false:

D2 receptor antagonist drugs have weak anti-sickness properties

Answer 17

FALSE:
They have powerful anti-emetic properties

Phenophiazines - morning sickness
Metoclopramide
Doperidone (Motilium)

Quite a lot of SEs

Question 18

What is the drug of choice for chemo sickness and post op sickness?

Answer 18

ONDANSETRON (5HT3 Antagonist)

Question 19

Name some 5HT3 Receptor antagonist drugs for nausia:

Answer 19

ONDANSETRON - drug of choice for chemo + post op
GRANISETRON
POLONOSTERON
TROISETRON

Question 20

What category do these drugs fall under?

• APREPITANT
• FOSAPREPITANT
• CASOPITANT
• MAROPITANT

Answer 20

They are NK1 Receptor Antagonists

Aprepitant is a substance P antagonist used for chemo and post op n/v.

Question 21

What NK1 Receptor Antagonist is a Substance P antagoinst

Answer 21

APREPITANT (P is for substance P)

Question 22

What is the ‘non selective antagonist’ drug which is the drug of choice for motion sickness?

Answer 22

HYCOSINE SCOPOLAMINE
is it a non-selective antagonist and is the drug of choice for motion sickness. Given orally / TD patch.

SE: Dry mouth, blurred vision, less sedative that anti-histamines (H1 antagonists)

Question 23

What class of Drug are histamine antagonists?

Answer 23

H1 Antagonists:
Cyclasine,
Cinnarizine,
Promethazine.

(zzzzzs for sleepiness)

Question 24

What class of anti-emetics does ‘MARINOL’ fall under?

Answer 24

Cannabinoids

Question 25

What corticosteroid can be used to treat vomiting?

Answer 25

DEXAMETHASONE

• Used in vomitting caused by chemotherapy
• Mechanism not fully known
• Used in combo with D2 or 5HT3 antagonists (causes improved action)

May also increase apatite

Question 26

When would you be able to give a therapeutic EMETIC?

Answer 26

• If someone had ingested a poisonous substance
• Drug overdose
• Alcohol Intoxication

NOT:

• Unconscious Patients
• Kerosine Poisoning
• CNS Stimulant/morphine overdose
• Ingestion of Corrosive substances

Question 27

Name some therapeutic Emetics:

Answer 27

• Syrup of Ipecac (ipecacanta) - oral works in 15 mins
• Apomorphine - IM/SC works in 10/15 mins
• Activated Charcoal -MOST COMMONLY USED

Question 28

What is the most commonly used Emetic?

Answer 28

Activated Charcoal