Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

LCRS Pharmacology and Therapeutics > Anti-emetics > Flashcards

Anti-emetics Flashcards

1
Q

What are the major classes of anti-emetics?

A 
Mixed receptor antagonists
Dopamine type 2 receptor antagonists
Muscarinic receptor antagonists
Serotonin (5HT3) receptor antagonists
Cannabinoids
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the definition of nausea?

A

Subjective, unpleasant sensation in throat and stomach, often precedes vomiting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the definition of vomiting?

A

Forceful propulsion of stomach contents out of the mouth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What often precedes both nausea and vomiting?

A

Salivation
Sweating
Tachycardia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What happens in the process of vomiting?

A

Stomach, oesophagus and associated sphincters are relaxed
Tension in gastric and oesophageal muscles trigger afferent nerve impulses
Contraction of upper small intestine, pyloric sphincter and pyloric region of stomach
Contents of upper jejunum, duodenum and pyloric region of stomach move into body and fundus of stomach
Lower and upper oesophageal sphincters and oesophagus relax
Retching/vomiting then may occur

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the consequences of acute nausea?

A

Interferes with mental and physical activity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the consequences of severe vomiting?

A

Very debilitating
Dehydration
Loss of gastric hydrogen and chloride ions may lead to hypochloraemic metabolic alkalosis (raised blood pH)
Contributes to reduction in renal bicarbonate exertion and increase in bicarbonate reabsorption
This is accompanied by increased sodium reabsorption in exchange for potassium leading to hypokalaemia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the vestibular system particularly important in for children?

A

Motion sickness

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the result of lots of CNS inputs into the emetic pathway?

A

If you see something disturbing or smell something disgusting it could induce vomiting- several cortical inputs that influence vomiting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What in the stomach is responsible for feeding back to vomiting centre and triggering nausea and vomiting?

A

Mechanoreceptors and chemoreceptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How can vomiting be a life saving protection system?

A

The vomiting centre and CTZ sit in a location in the brain that has a very porous BBB so vomiting centre and CTZ act as an early warning system to protect brain from toxin damage as these toxins will stimulate vomiting centre and CTZ and trigger vomiting before they have a chance to cross BBB and affect CNS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are the targets for anti-emetic drugs?

A

Vestibular system
Cortex
CTZ
Peripheral pathways

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is an example of a mixed receptor antagonist?

A

Promethazine- phenothiazine derivative

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is promethazine’s mode of action?

A

Competitive antagonist at following receptors in order of potency:
Histaminergic (H1)
Cholinergic (Muscarinic, M)
Dopaminergic (D2)

It acts centrally (vestibular nucleus, CTZ and vomiting centre) to block activation of vomiting centre

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the difference between promethazine and other phenothiazines which are used as neuroleptic drugs?

A

Different oder of potency with greater antagonistic effects at D2 receptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

When is promethazine used as an anti-emetic?

A

Motion sickness- used prophylactically but some benefit may be gained if it’s taken after onset of nausea and vomiting
Disorders of the labyrinth e.g. Meniere’s disease
Hyperemesis gravidarium
Pre and post operatively

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What else is promethazine used for?

A

Because of its effect in histamine blockade and its sedative effects, it’s also useful for:
Relief of allergic symptoms
Anaphylactic emergency
Night sedation, insomnia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is hyperemesis gravidarium?

A

Complication of pregnancy characterised by severe nausea and vomiting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the pharmacokinetics of promethazine like?

A

Administered orally
Onset of action 1-2 hours so need to give relatively in advance to someone that is travelling
Maximum effect at around 4 hours
Duration of action 24 hours

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What unwanted effects of promethazine are there?

A 
Dizziness
Tinnitus
Fatigue
Sedation
Excitation in excess
Convulsions
Anti-muscarinic side effects
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Give two examples of dopamine (D2) receptor antagonists

A

Metoclopramide and domperidone

22
Q

What is the order of potency of dopamine receptor antagonists?

A

D2>H1>Muscarinic receptors

23
Q

Where do dopamine receptor antagonists work?

A

Centrally especially at CTZ

24
Q

What effect do dopamine receptor antagonists have?

A

Prokinetic effects in GI tract:
Increases smooth muscle motility (from oesophagus to small intestine)
Accelerated gastric emptying
Accelerates transit of intestinal contents (from duodenum to ileo-caecal valve)

25
Q

What causes pro kinetic effects on GI tract of dopamine receptor antagonists?

A

Antagonism of inhibitory effect of dopamine on myenteric neurones

26
Q

Why are dopamine receptor antagonists not very good at treating motion sickness?

A

Only blocking the dopamine receptors in CTZ and not blocking rest of signals going directly from vestibular system to vomiting centre

27
Q

What are metoclopramide and domperidone used to treat?

A

Treat nausea and vomiting associated with:
Uraemia
Radiation sickness
GI disorders
Cancer chemotherapy (high doses)
Parkinson’s disease treatments that stimulate dopaminergic transmission

28
Q

Why can you give domperidone to Parkinson’s patients who are having bad nausea and vomiting because of Parkinson’s drugs?

A

It will only block dopamine receptors in CTZ and won’t interfere with dopamine transmission elsewhere that the anti-Parkinson’s drugs are working on

29
Q

How are dopamine receptor antagonists given?

A

Orally- rapidly absorbed but extensive first pass metabolism

IV

30
Q

What is the difference between metoclopramide and domperidone in terms of BBB?

A

Metoclopramide can cross the BBB- it has potential CNS side effects
They can also cross the placenta

31
Q

Why must care be taken with bioavailability of coadminstered drugs with dopamine receptor antagonists?

A

Because of the pro-kinetic effects of these drugs- they increase the rate of transit through GI tract so could reduce chance of some drugs being sufficiently absorbed
Furthermore nutrient supply may be compromised which is important in conditions like DM

32
Q

What are the unwanted effects of dopamine receptor antagonists?

A

In the CNS (metoclopramide only):
-Drowsiness
-Dizziness
-Anxiety
-Extrapyrimidial reactions- children are more susceptible
Parkinsonian like syndrome- rigidity, tremor and motor restlessness
In the endocrine system:
Dopamine exerts negative influence on prolactin release so there is:
-Hyperprolactinaemia
-Galactorrhea
-Disorders of menstruation

33
Q

Give an example of muscarinic receptor antagonist

A

Hyoscine

34
Q

What is the antagonist potency of hyoscine?

A

Muscarinic»>D2=H1

35
Q

Where does hyoscine act?

A

Centrally, especially in vestibular nuclei, CTZ and vomiting centre to block activation of vomiting centre

36
Q

What is hyoscine used for?

A

Anti-emetic:
Prevention of motion sickness (only works prophylactically)
In operative pre-medication

37
Q

What are the targets of hyoscine?

A

Direct actions on vestibular system and some weak action on dopamine receptors

38
Q

Why are muscarinic receptor antagonists very good anti-emetics?

A

There is decreased feed from projections from vestibular system to the CTZ and there are muscarinic receptors in vomiting centre as well, you also inhibit pathways coming into the vomiting centre

39
Q

How are muscarinic receptor antagonists administered?

A

Orally or via transdermal patch

40
Q

What are the unwanted effects of muscarinic receptor antagonists?

A 
Typical anti-muscarinic side effects:
Drowsiness
Dry mouth
Cycloplegia
Mydriasis
Constipation
41
Q

Give an example of a serotonin (5-hydroxytryptophan) receptor antagonists (5-HT1)

A

Ondansetron

42
Q

What is ondansetron’s mode of action?

A

It blocks transmission in visceral afferents and CTZ

43
Q

What is ondansetron used for?

A

Anti-emetic:
Main use in preventing anti-cancer drug induced vomiting (especially cisplatin)
Radiotherapy induced sickness
Post operative nausea and vomiting

44
Q

Where are 5HT receptors found?

A

Driving a lot of pathways coming from periphery to trigger felling of nausea and vomiting within the CTZ
Within the CTZ itself that respond to a lot of drugs that cause nausea and vomiting particularly chemotherapy type compounds- blocks 2 pathways hence why it’s so effective

45
Q

What are the pharmacokinetics of ondansetron?

A

Orally administered
Well absorbed
Excreted in the urine

46
Q

What are the unwanted effects of ondansetron?

A

Headache
Sensation of flushing and warmth
Increased large bowel transit time (constipation)

47
Q

What is ondansetron commonly used in combination with?

A

5-HT receptor antagonists may be used for low emetogenic chemotherapy but they may be used in combination with corticosteroids for high or moderately high emetogenic chemotherapy- improved efficacy may be due to anti-inflammatory properties of corticosteroids

48
Q

What common drug can also be used as an anti-emetic?

A

Cannabinoids-THC

Effective at treating emesis from anti-cancer drugs which other antiemetics aren’t effective against

49
Q

How do cannabinoids act as an anti-emetic?

A

It acts at a number of sites within CNS via CB1 receptors which are located presynaptically and decrease release of neurotransmitters associated with triggering vomiting process

50
Q

What else do cannabinoids do post emesis?

A

Inhibits prostaglandin synthesis which has been implicated in emesis from anti-cancer drugs

LCRS Pharmacology and Therapeutics (33 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions