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High Yield Review: Phase II MEQ Pros > Antiemetics > Flashcards

Antiemetics Flashcards

1
Q

What is the indication for Serotonin 5-HT3 receptors (ondansetron; palonosetron)?

A

Acute Nausea & Vomiting.

This is because they primarily bind to serotonin 5-HT3 receptors in the GIT, to prevent nausea and vomiting triggered by the presence of drug within the GIT (rather than in the blood)

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2
Q

How are serotonin 5-HT3 antagonists administered?

A

Oral or IV administration

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3
Q

Describe the mechanism of actions of serotonin 5-HT3 antagonists (ondansetron)

A

Serotonin 5-HT3 antagonists -> blocks / inhibits serotonin 5-HT3 receptors
- peripherally at the gastrointestinal tract and peripheral nerve terminals
- centrally at the area postrema and chemoreceptor trigger zone in the nucleus at tractus solitarius
These results in inhibition of vagus nerve stimulation -> peripheral and central antiemetic effect

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4
Q

Name 2 other drugs that can be combined with serotonin 5-HT3 to enhance its effect.

A
  1. Corticosteroids (Dexamethasone)

2. Neurokinin 1 receptor antagonists (aprepitant, fosaprepitant)

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5
Q

When do you give serotonin 5-HT3 antagonist for acute nausea & vomiting?

A

BEFORE.

Acts as a prophylaxis for acute nasuea and vomiting

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6
Q

What is the indication for neurokinin 1 antagonists (aprepitant; fosaprepitant)

A

Acute Nausea & Vomiting

Delayed Nausea & Vomiting

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7
Q

Describe the mechanism of actions of NK1 (receptor for substance P) antagonists.

A

NK 1 antagonists -> blocks/inhibit NK1 receptors in the central postrema and chemoreceptor trigger zone in the nucleus at tractus solitarius -> central antiemetic effect

Additional inhibition of substance P-induced vomiting due to antagonism.

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8
Q

How is aprepitant and fosaprepitant (prodrug of aprepitant) administered?

A

Aprepitant: oral administration
Fosaprepitant: IV administration

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9
Q

What are some adverse side effects of NK1 receptor antagonists?

A

Fatigue, dizziness, diarrhoea, abdominal pain

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10
Q

Any drug interaction with NK1 antagonists?

A

Aprepitant -> CYP34A inhibitor

Fosaprepitant -> CYP2D6 inhibitor

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11
Q

Name a drug of dopamine 2 receptor antagonists.

A

Metoclopramide.

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12
Q

What is the indication of metoclopramide / dopamine 2 receptor antagonists.

A
  • Mild Acute Nausea & Vomiting

- High Non-AC Delayed Nausea & Vomiting (combined with DEX)

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13
Q

Describe the mechanism of action of metoclopramide / dopamine 2 receptor antagonists.

A

Dopamine 2 receptor antagonists (Metoclopramide) -> blocks / inhibits D2 receptors at the area postrema and chemoreceptor trigger zone in the nucleus of tractus solitarius.

Additional cholinergic smooth muscle stimulation -> prokinetic effect

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14
Q

Name 2 adverse side effects or major concerns for Metoclopramide.

A

Hyperprolactinemia

  • Gynecomastia and impotence in men
  • Galactorrhoea and menstrual disturbance in women

Extrapyramidal side effects:

  • parkinsonism
  • dystonia
  • tardive dyskinesia
  • akathasia
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15
Q

Name a drug in muscarinic (M1) receptor antagonist used for nausea and vomiting.

A

Scopalamine (hyoscine)

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16
Q

What is the indication for Scopalamine?

A

Vestibular-induced nausea & vomiting (e.g. motion sickness)

17
Q

Describe the mechanism of action of Scopalamine.

A

Scopalamine (M1 receptor antagonists) -> inhibits / blocks M1 receptors at the area postrema and vestibular apparatus -> vestibular anti-emetic effect

18
Q

How are Scopalamine administered?

A

Transdermal patch administration

Because oral administration often result in high incidence of adverse side effects.

19
Q

Describe the adverse side effects of Scopalamine.

A

Anti-cholinergic side effects

  • Dry mouth
  • Urinary retention
  • Mydiasis (pupil dilation)
  • Tachycardia
  • Flushing
20
Q

Name one contraindication for Scopalamine.

A

Acute angle-closure glaucoma due to the anti-cholinergic properties.

21
Q

Name a drug of Histamine 1 Receptor Antagonist.

A

Diphenhydramine

22
Q

Describe the MOA of Diphenhydramine.

A

Diphenhydramine (Histamine 1 receptor antagonists) -> blocks / inhibits histamine 1 receptos in the area postrema and vestibular apparatus -> vestibular antiemetic effect

1st gen antihistamine also additionally blocks / inhibits muscarinic receptors

23
Q

Describe the major side effects of DIphenhydramine.

A
  • Antihistamine effect: sedation, drowsiness (as 1st gen antihistamine crosses BBB)
  • Anticholinergic effect:
    Dry mouth, urinary retention, mydriasis, tachycardia, flushing
24
Q

Name a drug of the class corticosteroids used for nausea and vomiting?

A

Dexamethasone

Mimics effects of glucocorticoids / cortisol but exact MOA for nausea and vomiting unknown

25
Q

Corticosteroids (e.g. dexamethasone) are often prescribed with which antiemetic to prevent acute and delayed vomiting?

A

Serotonin 5-HT3 antagonist

As it increases the sensitivity of serotonin 5-HT3 receptors when combined

26
Q

What are the major adverse side effects of dexamethasone?

A

Short term use not much side effects

Long term use can result in iatrogenic Cushing’s syndrome

27
Q

What are benzodiazepines?

A

GABA (gamma-aminobutyric acid) agonists

28
Q

What is the indication for benzodiazepines used for nausea and vomiting?

A

Anticipatory nausea and vomiting

Nausea and vomiting caused by anxiety

29
Q

Describe the MOA of benzodiazepines used as an antiemetics.

A

Benzodiazepines -> binds to allosteric site of GABA-alpha receptors -> increase chloride conductance -> anxiolytic

30
Q

What are the adverse side effects of benzodiazepines?

What happen if there is an overdose?

A

Sedation

Overdose -> respiratory depression

31
Q

Name an atypical antidepressant used for nausea and vomiting.

A

Olanzapine

32
Q

What is the usage of olanzapine (atypical antidepressant) for nausea and vomiting?

A

For the treatment of chemotherapy-induced nausea and vomiting

33
Q

Describe the mechanism of action of olanzapine.

A

They binds to and inhibits the following receptors:

  • Serotonin 5-HT3
  • Dopamine D1-D4 (not just D2)
  • Muscarinic M1
  • Histamine 1
34
Q

What is one adverse side effect of antipsychotics to take note of?

A

QT Interval prolongation

High Yield Review: Phase II MEQ Pros (10 decks)

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