Vomiting

Question 1

Serotonin 5-HT3 antagonist name?

Answer 1

Ondansetron 1st Gen
Palonosetron 2nd Gen

Question 2

MOA of Serotonin 5-HT3 antagonist?

Answer 2

Act at 5-HT3 receptors mainly in GIT due to chemo-drugs triggering serotonin release in GI that stimulate vagal afferents to initiate vomiting
CNS 5-HT3 receptors have no big role in nausea and vomiting”

Question 3

Uses of Serotonin 5-HT3 antagonist?

Answer 3

1. Efficacy enhanced by combination with a corticosteroid or NK1-receptor antagonist (better).
2. Given IV 30min or Orally 1hr before chemotherapy to prevent CINV
3. Generally ineffective for delayed nausea and vomiting >24hr after chemo.
4. Only for acute nausea and vomiting

Question 4

Corticosteroids names?

Answer 4

Dexamethasone
Methylprednisolone

Question 5

Uses of corticosteroids?

Answer 5

“Often used in:

In combination with 5-HT3 antagonists to prevent acute vomiting

For delayed vomiting in patients on moderately to highly emetogenic chemo regimens

Question 6

ADR of corticosteroids?

Answer 6

“1. Higher doses or long term use >2 weeks can cause iatrogenic Cushing’s syndrome
2. ADR unlikely with short-term use”

Question 7

Dopamine receptor antagonist name?

Answer 7

Metoclopramide

Question 8

MOA of metoclopramide?

Answer 8

Dopamine receptor antagonism in area postrema

Question 9

ADR of metoclopramide?

Answer 9

1. Extrapyramidal ADR:
   - Restlessness, dystonias, parkinsonian symptoms
   - Elderlies esp susceptible
   - Irreversible tardive dyskinesia on long-term usage
2. Hyperprolactinemia - Galactorrhea, gynaecomastia, impotence, menstrual disorders

Question 10

Neurokinin receptor antagonist name?

Answer 10

Aprepitant

Question 11

MOA of Neurokinin receptor antagonist

Answer 11

NK1 receptor antagonism in area postrema

Question 12

Uses of neurokinin receptor antagonist?

Answer 12

To prevent vomiting together with 5-HT3 receptor antagonists (acute) and corticosteroid (Delayed) caused by highly emitogenic chemo

Question 13

ADR of aprepitant?

Answer 13

Fatigue, dizziness, diarrhoea
Moderately inhibit CYP3A4
Drugs that inhibit CYP3A4 can influence plasma levels e.g. clarithromycin”

Question 14

Antipsychotics names?

Answer 14

Phenothiazine
Promethazine
Droperidol
Olanzapine

Question 15

MOA of antipsychotics?

Answer 15

1. Dopamine receptor antagonism (CTZ)
2. Muscarinic antagonism (vestibular system + vomiting centre)
3. Histamine receptor antagonism (vomiting centre + vestibular system)

Question 16

which antipsychotic has less EPS ADR?

Answer 16

Olanzapine

Question 17

ADR of antipsychotics?

Answer 17

“1. Sedative due to antihistaminergic effects
2. Extrapyramidal side effects (EPS)”

Question 18

NAmes of benzodiazepines?

Answer 18

Lorazepam
Diazepam

Question 19

MOA of benzos?

Answer 19

1. Bind to allosteric site on GABA receptors to raise chloride conductance, acting as positive allosteric modulators (PAMs)
2. Anxiolytic

Question 20

Use of benzos?

Answer 20

REduce anticipatory vomiting or anxiety-caused vomiting

Question 21

ADR of benzos

Answer 21

Sedative / hypnotic
Additive effects with other sedatives and CNS depressants - but respiratory depression on overdose
Banned in pregnancy, esp 1st trimester - risk of cleft palate

Question 22

Muscarinic receptor antagonist names?

Answer 22

Scopolamine

Question 23

MOA of scopolamine?

Answer 23

Muscarinic antagonist in vestibular system and vomiting centre

Question 24

ADR of scopolamine?

Answer 24

1. Anticholinergic ADR
2. High ADR when given orally
3. Transdermal patch 0.5-1hr before journey (preferred)