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Year 2 Pharma > Anti-emetics > Flashcards

Anti-emetics Flashcards

1
Q

Define nausea

A

subjective, unpleasant sensation in the throat and stomach; often precedes vomiting

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2
Q

Define vomiting

A

forceful propulsion of stomach contents out of the mouth.

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3
Q

What is the vomiting pathway

A
  • deep breath, glottis closes and the larynx rises to open the upper oesophageal sphincter. Soft palate elevates
  • diaphragm contracts sharply to create a negative intrathoriacic pressure to facillitate sphincter opening
  • whilst diaphragm contracts, abdominal walls contract to squeeze the stomach and raise intra gastric pressure. With the pylorus closed and the upper sphincters open, pressure escapes proximally
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4
Q

What are consequences of acute nausea

A

Interferes with mental/physical activity

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5
Q

What are consequences of severe vomiting

A

Dehydration
Loss of gastric HCl -> hypochloraemic metabolic alkalosis
Reduction in renal HCO3- excretion/increased reabsorption -> increased sodium reabsorption and potassium excretion -> hypokalaemia

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6
Q

Where does the vomiting centre and chemoreceptor trigger zone sit

A

In a location of the brain with v porous BBB in the medulla

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7
Q

Where can drugs interefere with the vomiting and nausea pathway

A

Vestibular system
Chemoreceptor trigger zone
Cortex
Peripheral pathways eg 5HT3 receptors in GI and mechanoreceptors and chemoreceptors

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8
Q

What is an example of a mixed receptor antagonist

A

Promethazine

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9
Q

What cranial nerves mediate signals to stomach/heart to vomit

A

CN9 and 10

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10
Q

MoA of promethazine

A

Competitive antagonist at histaminergic, cholinergic and dopaminergic receptors (potency goes in this order too), acting centrally (vestibular nucleus, CTZ and vomiting centre) to block the activation of the VC

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11
Q

When is promethazine used

A 
As an atni emetic:
motion sickness
disorders of the labyrinth (eg menieres disease)
hyperemesis gravidarium (pregnancy complication)
Pre and post op
allergy relief
anaphylaxis
night sedation
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12
Q

Administration, onset of action and duration of action of promethazine

A

Administation oral
Onset of action 1-2 hr
Duration of action 24 hr

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13
Q

What are unwanted side effects of promethazine

A 
Dizziness
Tinnitus
Fatigue
Excitation in excess
Sedation
Convulsions
Anti muscarinic effects
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14
Q

What are examples of d2 receptor antagonists

A

Metoclopramide,

Domperidone

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15
Q

What is the receptor antagonistic potency order for d2 receptor antagonists

A

D2&raquo_space;> H1&raquo_space;> muscarinic receptors

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16
Q

MoA of d2 receptor antagonists

A

Acts centrally, especially on the CTZ.

17
Q

Why do d2 receptor antagonists not combat motion sickness

A

Since they block D2 receptors in the CTZ but they don’t block the rest of the signals going directly from the vestibular system

18
Q

Effects of d2 receptor antagonists on GI

A

Prokinetic effects (effects of PNS) eg increase in SM motility, accelerate gastric emptying, accelerate transit through tract. Less to vomit

19
Q

What are uses of d2 receptor antagonists

A

Uraemia
Cancer chemotherapy in high doses
Parkinsons disease treatment as they block large DA transmission induced by parkinsons drugs (only in CTZ)

20
Q

Administration of metoclopramide and domperidone

A

Oral (extensive 1st pass metabolism) and IV

21
Q

Do metoclopramide and domperidone cross the BBB or placenta

A

They cross both.

This causes CNS side effects and care must be taken about the bioavailability of the drugs

22
Q

what happens if metoclopramide or domperidone are taken with digoxin

A

Absorption or effectiveness of digoxin can be reduced

23
Q

What is important about metoclopramide and domperidone in diabetes mellitus patients

A

Nutrient supply might be compromised

24
Q

What are unwanted side effects of metoclopramide and domperidone

A 
In CNS (mainly metoclopramide):
drowsiness, dizziness, anxiety, extrapyramidal reactions - parkinsons like symptoms
In endocrine system: hyperprolactinaemia, galactorrhoea, disorders of menstruation
25
Q

What is the receptor antagonistic potency order for muscarinic receptor antagonists

A

Muscarinic&raquo_space;> D2/H1

26
Q

What are examples of muscarinic receptor antagonists

A

Hyoscine

27
Q

Where does hyoscine act, and how

A

Centrally, especially on vestibular nuclei, CTZ and vomiting centres to block activation and prevent motion sickness. However little effect once nausea establised

28
Q

When is hyoscine used

A

In pre op medication

29
Q

Adminstation of hyoscine

A

Oral (peak effect in 1-2 hrs)
IV
Transdermal

30
Q

What are unwanted side effects of hyoscine

A

Anti muscarinic side effects - blocked PNS

Drowsiness, dry mouth, cycloplegia (paralysis of cililary muscles), mydriasis, constipation

31
Q

What is an example of a serotonin (5-HT3) receptor antagonist

A

Ondansetron

32
Q

What does ondansetron do

A

Blocks transmission in visceral afferents (vagus and splanchnic nerves) and CTZ. This CTZ block and from the peripheries makes it good at treating sickness from chemo and radio

33
Q

What are uses of ondansetron?

A
  • preventing anti cancer drug induced vomiting
  • radiotherapy induced sickness
  • post op nausea and vomiting
34
Q

administration of ondansetron

A

Oral (well absorbed, excreted in urine - need good renal function)

35
Q

What are unwanted side effects of ondansetron

A

Headache
Sensation of flushing and warmth
Constipation - increased large bowel transit time

36
Q

What happens when ondansetron is used in combination with corticosteroids

A

5-HT3 receptor antagonist that can be used for low emetogenic chemotherapy. Corticosteroids may be used in combination for high or moderately high emetogenic chemotherapy and improved efficacy of combined therapy may be due to anti inflammatory properties of corticosteroids

37
Q

What can cannabinoids treat in an anti emetic way

A

Treats emesis from anti cancer drugs when other anti emetics are not effective eg cisplatin

38
Q

MoA of cannabinoids working as anti emetics

A

Acts via CB1 receptors located pre synaptically to decrease release of NTs associated with vomiting. Also inhibit prostaglandin synthesis which is implicated in emesis from anti cancer drugs

Year 2 Pharma (34 decks)

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