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Year 2 - LCRS - Pharmacology > Anti-emetics (10.03.2020) > Flashcards

Anti-emetics (10.03.2020) Flashcards

1
Q

CINV

A

Chemotherapy induced nausea & vomiting (CINV)

  • e.g. cisplatin
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2
Q

Treatment of CINV

A

Triple Therapy:

  • Ondansetron - 5-HT3A receptor antagonist (used for early stage N&V)
  • Glucocorticoids - reduce free radical production (used for late stage N&V)
  • Aprepitant - neurokinin-1 receptor antagonist (used for late stage N&V)
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3
Q

Ondansetron

A

= 5-HT3A receptor antagonist

  • 5-HT3A receptors are found on nerve fibres going to CTZ
  • dansetron = 5HT receptor antagonist
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4
Q

Promethazine

A
  • Promethazine - H1 receptor antagonist (expressed vestibular nuclei which are activated due to neural mismatch in motion sickness)
  • used in motion sickness
  • OTC
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5
Q

Hyoscine (scopolomine)

A

– non-selective muscarinic receptor antagonist

  • centrally acting non-selective muscarinic receptor antagonist
  • acts on CTZ and VC -> not only used for motion sickness but also in end-of-life care.
  • SE: constipation, dizziness, drowsiness, dry mouth, dyspepsia…
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6
Q

Metoclopramide

A

Dual action

  • Dopamine D2 receptor antagonist
    • Prokinetic – stimulates gastric emptying
    • Inhibits D2 receptors in CTZ
  • 5-HT3A receptor antagonist
    • Inhibits activation of CTZ

would be also good to treat drug induced N&V?

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7
Q

Pathophysiology of CINV

A
  • chemotherapy agent (e.g. cisplatin) is toxic to cells and causes release fo free radicals leading to excessive 5HT release
  • 5HT activates 5HT3A receptors on nerve fibres to chemoreceptor trigger zone (CTZ)
  • CTZ activates nerve fibres going to the vomiting center (muscarinic receptors 1-5 at VC)
  • activation of the VC causes N&V
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8
Q

What is vomiting

A

the forceful oral expulsion of gastric contents.

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9
Q

Neurokinin 1 receptor antagonists in CINV treatment

A
  • neurokinin 1 R is found in area posterma of the VC
  • activated by substance P (which is related from higher centres of the brain and is involved in pain perception)
  • used for late N&V in CINV
  • e.g. aprepitant
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10
Q

Biphasic response fo N&V

A

in CIMV

early N&V -> Ondansetron (5HT3A R antagonist)
late N&V -> GC and neurokinin-1 R antagonist

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11
Q

Pathophysiology of motion sickness

A
  • Labyrinth - neural mismatch between what you see and what you feel -> activates histamine1 receptors on vestibular nuclei
  • Vestibular nuclei activate muscarinic (M1-5) receptors on CTZ
  • CTZ activates VC, which causes nausea
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12
Q

Where are the muscarinic receptors in the pathway that causes nausea?

A
  • on the VC
  • also on CTZ
  • activation of the M1-5 muscarinic receptors -> N&V
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13
Q

Treatment of motion sickness

A
  • Promethazine - H1 receptor antagonist

- Hyoscine (scopolomine) – non-selective muscarinic receptor antagonist

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14
Q

Gastroparesis

A
  • delayed emptying of the stomach

- reduced stomach contraction

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15
Q

Pathophysiology of gastroparesis

A
  • 5-HT – activates 5-HT3A receptors on CTZ
  • CTZ activates nerves fibres to vomiting centre (VC)
  • VC -> nausea
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16
Q

Where is the pathogenesis leading to N&V not well understood?

A
  • in pregnancy

- as a reaction to seeing or hearing something repulseive

17
Q

Physiological control of N&V

A
  • Chemoreceptor Trigger Zone (CTZ): receives multiple inputs from areas including stomach & vestibular nuclei
  • CTZ: communicates with the vomiting centre -> nausea & vomiting
18
Q

Mechanistic triggers to N&V

A

Cytotoxic drugs, motion sickness, gastrointestinal problems, pregnancy, other higher functions

19
Q

What are the main classes of anti-emetic drugs?

A
  • 5-HT3A receptor antagonists (e.g. Ondansetron)
  • Histamine H1 receptor antagonists (e.g. Promethazine)
  • Muscarinic receptor antagonists (e.g. hyoscine = scopolomine)
  • Dopamine D2 receptor antagonists (e.g. Metoclopramide but this also acts as a 5HT3A R antagonist)
20
Q

When are the different classes of anti-emetic drugs used?

A
  • 5-HT3A receptor antagonists: chemotherapy induced N&V (e.g. Ondansetron)
  • Histamine H1 receptor antagonists: motion sickness
  • Muscarinic receptor antagonists: motion sickness (e.g. hyoscine = scopolomine)
  • Dopamine D2 receptor antagonists: gastroparesis induced N&V
21
Q

What are the SEs of the different anti-emetics?

A
  • 5-HT3A receptor antagonists: Headaches, constipation
  • Histamine H1 receptor antagonists: drowsiness
  • Muscarinic receptor antagonists: dry mouth, drowsiness
  • Dopamine D2 receptor antagonists: galactorrhoea, extrapyramidal SE
22
Q

Treatment of gastroparesis induced N&V

A

Metoclopramide:

  • Dopamine D2 receptor antagonist &
  • 5-HT3A receptor antagonist

Year 2 - LCRS - Pharmacology (34 decks)

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