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CPT > Antiemetics And Antidiarrhoeals > Flashcards

Antiemetics And Antidiarrhoeals Flashcards

1
Q

What is the vomiting centre in the brain and what is it called?

A
  • is in medulla

- Chemoreceptor Trigger Zone

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2
Q

What triggers the Chemoreceptor Trigger Zone?

A
  • sensory afferents via midbrain
  • vestibular nuclei
  • vesicular afferents from gut
  • direct triggers
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3
Q

What classes of drugs target the vestibular nuclei?

A
  • muscarinic receptor antagonist

- H1 receptor antagonist

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4
Q

What classes of drugs affect the visceral afferents from the gut?

A
  • 5HT3 antagonist

- D2 receptor antagonist

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5
Q

What classes of drugs affect the CTZ?

A
  • D2 receptor antagonist
  • 5HT3 receptor antagonist
  • Muscarinic receptor antagonist
  • H1 receptor antagonists
  • corticosteroids
  • cannabinoids
  • NK1 receptor antagonists
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6
Q

Hyoscine hydrobromide (muscarinic receptor antagonist)

A
  • acts on vestibular nuclei and sometimes CTZ
  • competitive blockade of ACTH receptor
  • ACTH part of parasympathetic system so some effects and side effects mimic parasympathetics
  • first line for motion sickness, useful for long journey

Good for:

  • people who can’t take tablets (patch version)
  • motion sickness
  • bowel obstruction

Side effects

  • sedation
  • memory problems
  • glaucoma
  • dry mouth and constipation
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7
Q

H1 receptor antagonists (cyclizine, levomepromazine, cinnirazine, promethazine, diphenhydramine)

A
  • centrally acts on vestibular nuclei
  • inhibits histaminergic signals from the vestibular system to the CTZ in medulla

Good for

  • motion sickness (long plane journeys)
  • promethazine for morning sickness in pregnancy

Not good for

  • cyclizine on little old ladies and children (causes excitation)
  • if you’re car driving because you nee to concentrate

Side effects

  • sedation
  • excitation
  • antimuscarinic: dry mouth, constipation, urinary retention
  • cardiac toxicity: long QT interval
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8
Q

5HT3 receptor antagonist (Ondansetron, granesitron, palonosetron)

A
  • acts on visceral afferent in the gut
  • peripherally: reduces GI motility and GI secretions
  • centrally: acts to inhibit the CTZ
  • Good for almost everyone: often first line treatment

Side effects

  • constipation
  • headache
  • elevated liver enzymes
  • long QT syndrome
  • extra-pyramidal effects: dystocia, Parkinsonism
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9
Q

Metoclopramide

A
  • D2 receptor antagonist
  • acts on visceral afferents in gut
  • increases ACh at muscarinic receptors in the gut
  • promotes gastric emptying
  • increases tone at LOS so it closes
  • increases tone and amplitude of gastric contractions
  • decreases tone of pylorus so it opens
  • increases peristalsis
  • good for: GORD and ileum

Side effects

  • galactorrhoea via prolactin release
  • extra pyramidal effects: dystonia, Parkinsonism
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10
Q

Domperidone

A
  • D2 receptor antagonist
  • acts on visceral afferents in the gut
  • similar MOA as metoclopramide
  • used frequently BEFORE but new evidence showed increased risk of CVS side effects
  • good for: improving lactation in breastfeeding mothers

Side effects

  • sudden cardiac death
  • galactorrhoea
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11
Q

Anti-psychotics (prochlorperazine, haloperidol)

A
  • D2 receptor antagonists
  • the “zines”
  • act on CTZ
  • may also block H2 and muscarinic receptors
  • good for: motion sickness, vertigo
  • prochlorperazine good in pregnancy
  • haloperidol: acts on CTZ and good in chemo and palliation

Side effects

  • extra pyramidal effects: dystonia, Parkinsonism
  • sedation
  • hypotension
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12
Q

Corticosteroids (dexamethasone, methyprednisolone)

A
  • acts on CTZ
  • may also have D2 receptor antagonist properties

Good for

  • perioperative nausea and vomiting
  • chemo
  • palliation: helps with eating

Side effects

  • insomnia
  • increase in appetite and blood sugar
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13
Q

Cannabinoids (nabilone)

A
  • acts on CTZ
  • good for chemo
  • used as LAST LINE

Side effects

  • dizziness
  • drowsiness
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14
Q

Neurokinin 1 receptor antagonist (aprepitant, fosaprepitant, netupitant)

A
  • prevents action of substance P at CTZ and in peripheral nerves
  • boosts effects of 5HT3 receptor antagonist
  • anxiolytics and antidepressant properties
  • good for chemo especially delayed emesis

Side effects

  • headache
  • diarrhoea
  • Stevens-Johnson syndrome
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15
Q

What is the first line treatment in general for emesis?

A
  • ondansetron and/or cyclizine

- then add dexamethasone if needed

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16
Q

What is the first line treatment for hyperemesis gravidarum?

A
  • promethazine or prochlorperazine
  • then add metoclopramide if needed
  • then add ondansetron if needed
17
Q

Loperamide

A
  • opioid receptor agonist
  • specific to moo receptors in the myenteric plexus
  • decreases tone of longitudinal and circular smooth muscle
  • reduces peristalsis but increases segmental contractions
  • decreases colonic mass movements by suppressing gastrocolic reflex
  • safe but effective in 48 hours
  • for diarrhoea
18
Q

Codeine and morphine

A
  • similar effects to loperamide
  • more often used when patients also have pain
  • ex: pt. Has appendicitis and diarrhoea

Side effects

  • paralytic ileus
  • nausea and vomiting
  • sedation and addiction
19
Q

Osmotic laxatives (lactulose, movicol, cosmocol)

A
  • for constipation
  • increases the amount of water in large bowel
  • draws fluid in (lactulose)
  • retain the fluid they came with (movicol and cosmocol)
20
Q

Stimulant laxatives (bisacodyl, sodium picosulphate, senna, co-danthromer, docusate sodium)

A
  • increase intestinal motility
  • may be given orally or per rectum
  • docusate sodium acts as stimulant and stool softener
  • glycerin suppositories cause rectal irritation and lubrication
21
Q

Bulk forming laxatives (ispaghula husk, methylcellulose)

A
  • medicinal fibre
  • helps to bulk stools
  • can help in constipation and diarrhoea
22
Q

Stool softeners (docusate sodium, glycerin suppository, arachis oil, liquid paraffin)

A
  • decrease surface tension of stool
  • increase penetration of fluid into stool
  • mostly enemas

CPT (16 decks)

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