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Gastro > Drugs for nausea and vomiting > Flashcards

Drugs for nausea and vomiting Flashcards

1
Q

Antiemetics examples (7)

A

1) Serotonin 5-HT3 antagonists
2) Corticosteroids
3) Neurokinin receptor antagonists
4) Dopamine receptor antagonists
5) Muscarinic receptor antagonists
6) H1 histamine receptor antagonists
7) Benzodiazepines

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2
Q

Cause of vomiting (4)

A
  1. area of POSTREMA of the floor of the fourth ventricle (no BBB) - detection of noxious substance in blood by chemoreceptor trigger zone
  2. GI tract - detection of noxious substance/ distention during bloating by chemoreceptors/ mechanical receptors
  3. vestibular system - detect motion (cause of motion sickness)
  4. higher centres of CNS - detect pain, mood, anxiety etc
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3
Q

most suitable drugs for LOW risk ACUTE nausea & vomiting from CHEMOTHERAPY

A

1 5HT3 antagonist

OR
2. DEX (corticosteroids)
OR
3. DOP (dopamine receptor antagonist)

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4
Q

most suitable drug for MODERATE risk ACUTE N&V from CHEMOTHERAPY

A
  • 5HT3 antagonist + dexamethasone
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5
Q

most suitable drug for HIGH risk ACUTE N&V from CHEMOTHERAPY/ CARBOPLATIN

A

5HT3 antagonist + dexamethasone + NK1-receptor antagonist

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6
Q

serotonin 5-HT3 antagonists examples

A

ONDANSETRON, Granisetron, palonosetron; “-setron”

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7
Q

Name an example of (1) a first-generation and (2) a second-generation 5-HT3 antagonist anti-emetic. State the half-life of these drugs.

A

(1) First-generation:
* Ondansetron (half-life 4-9 hrs)
(2) Second-generation:

Granisetron: half-life 9-12 hrs in cancer patients
Palonosetron: half-life 40-50 hrs

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8
Q

5HT3 antagonist MOA

A
  • block 5HT3 in GIT, prevents vomiting signals to be transmitted from GIT to CNS
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9
Q

indications for 5HT3 receptor antagonists

A
  • prevent acute CHEMOTHERAPY induced vomiting (not for delayed N&V >24)
  • any nausea caused by noxious GIT stimulation, eg small bowel obstruction
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10
Q

5HT3 antagonist dosage for chemotherapy induced vomiting prevention

A
  • IV 30mins before
    OR
  • oral 1 hour before
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11
Q

adverse effects of 5HT3 antagonist

A
  • headache, dizziness, drowsiness
  • constipation OR diarrhea
  • SMALL risk for cardiac arrhythmia
  • AVOID in 1st trimester of pregnancy (orofacial malformation)
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12
Q

DDI for 5HT3 antagonist

A
  • extensively metabolized by CYP450 enzymes
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13
Q

Corticosteroids examples

A

DEXAMETHASONE, methylprednisolone

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14
Q

corticosteroid MOA

A
  • Mimic effects of endogenous cortisol, MOA unknown
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15
Q

corticosteroid indications

A

– used in combination with 5-HT3 antagonists to prevent acute and delayed nausea and vomiting in patients on moderately to highly emetogenic CHEMOTHERAPY regimens

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16
Q

adverse effects of corticosteroids

A
  • iatrogenic cushing’s syndrome at high dose/ LT use
17
Q

dopamine receptor antagonist example

A

METOCLOPRAMIDE

18
Q

dopamine receptor antagonists MOA

A
  • block D2 receptor in the chemoreceptor trigger zone (CTZ)
  • prokinetic -> stimulate GI motility (useful for impaired bowel movement)
19
Q

dopamine receptor antagonist indications

A
  • nausea triggered by toxin in blood (CTZ detection)
  • impaired bowel movement (CANNOT USE FOR COMPLETE OBSTRUCTION)
20
Q

dopamine receptor antagonist adverse effects

A

Extrapyramidal side effects:
- Restlessness, dystonia, and parkinsonian symptoms
- LT -> irreversible tardive dyskinesia (thus only used for ST)

Elevated prolactin levels causing:
- Galactorrhoea, menstrual disorders, gynaecomastia, impotence

21
Q

neurokinin (NK1) receptor antagonist examples (aka substance P antagonists)

A

APREPITANT (oral), fosaprepitant (IV); “-pitant”

fosaprepitant is prodrug of aprepitant

22
Q

NK1 receptor antagonist MOA

A
  • act at NK1 receptor in chemoreceptor trigger zone
23
Q

NK1 receptor antagonist indication

A

combine with corticosteroid + 5-HT3 receptor antagonists to
prevent ACUTE and DELAYED n&v caused by highly emetogenic chemotherapy

24
Q

NK1 antagonist adverse effects

A
  • fatigue, dizziness, diarrhoea

DDI:
- metabolised by CYP3A4 -> interact with various chemotherapeutic agents

25
Q

most suitable drug for HIGH risk DELAYED n&v from CHEMOTHERAPY

A
  • DEX + OLZ (olanzapine)/ MCP (metoclopramide)/ ACR (aprepitant)
26
Q

antipsychotics: mixed dopamine/ muscarinic/ histamine receptor antagonist examples (3)

A

Phenothaizines
- PROCHLORPERAZINE, promethazine (dopamine & muscarinic antagonist + antihistamine)

Butyrophenones:
- DROPERIDOL (dopamine receptor antagonism and weak histamine receptor antagonism)

Atypical antipsychotic
- OLANZAPINE (dopamine, muscarinic & histamine receptor antagonism)

27
Q

antipsychotics MOA

A
  • dopamine receptor antagonism -> chemoreceptor trigger zone
  • muscarinic antagonism -> vomiting center & vestibular system
  • antihistamine -> vomiting center & vestibular system, less impt)
28
Q

antipsychotics adverse effects

A

– Sedative (due to antihistaminergic effects)
– Extrapyramidal syndrome [EPS]
– Hypotension
– Droperidol: prolongation of the QT interval

29
Q

most suitable drug for ANTICIPATORY n&v

A

benzodiazepines

30
Q

benzodiazepines examples

A

LORAZEPAM, diazepam

31
Q

benzodiazepines MOA

A
  • binding to an allosteric site on GABAA receptors increases chloride conductance
  • anxiolytic
  • reduce anticipatory vomiting or vomiting caused by anxiety
32
Q

benzodiazepine adverse effects

A
  • sedative / hypnotic; additive effects with other sedative drugs and CNS depressants e.g., antidepressants, alcohol and opioids
  • respiratory depression on overdose
  • AVOID during first trimester (risk of cleft palate)
33
Q

drugs used for treatment of motion sickness (2)

A

muscarinic antagonist
- scopolamine (HYOSCINE), diphenhydramine

34
Q

hyoscine MOA

A
  • antimuscarinic -> act on vestibular system and vomiting center
  • antispasmodic due to muscarinic antagonism -> use for abdominal cramps
35
Q

hyoscine indications

A
  • prevent motion sickness
  • abdominal cramps
36
Q

hyoscine adverse effects

A
  • dry mouth, blurring of vision
  • sedation, confusion
37
Q

diphenhydramine MOA

A
  • mixed h1 antihistamine (vomiting centre input and vestibular system) & M1 muscarinic receptor antagonist (vomiting center and vestibular system)
38
Q

diphenhydramine adverse effects

A
  • Sedative (H1 receptor antagonism)

Anticholinergic adverse effects:
- Dry mouth, blurring of vision, constipation

Gastro (20 decks)

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