Anti-emetics

Question 1

Classes of anti-emetics

Answer 1

Corticosteroids, serotonin 5-HT3 antagonist, Neurokinin-R antagoinst, Dopamine-R antagonist, anticholinergics, antihistamine/anticholinergic, antipsychotics, benzodiazepine

Question 2

Corticosteriods

Answer 2

Dexamethasone

Question 3

MoA of corticosteroids

Answer 3

Basis of anti-emetic effect unknown

Used with 5-HT3 antagonist for acute & delayed CINV

Question 4

SE of corticosteroids

Answer 4

Unlikely with short-term use.

Long term use (>2w) –> iatrogenic Cushing’s syndrome (rounded face, muscle wasting, easy bruising, immunosuppression)

Question 5

5-HT3 antagonist

Answer 5

Ondansetron (1G), Palonosetron (2G)

Question 6

MoA of 5-HT3 antagonist

Answer 6

Acts on GIT 5-HT3 receptors –> prevents activation of vomiting centre

Question 7

Use of 5-HT3 antagonist

Answer 7

Use with corticosteroid, NK-R antagonist

Prevents acute CINV not delayed

Question 8

SE of 5-HT3 antagonist

Answer 8

Generally well-tolerated but may cause h/a, dizziness, constipation
Ondansetron: dose reduction with hepatic insufficiency, small risk of arrhythmia
CYP450 metabolism — clearance may be affected

Question 9

Neurokinin receptor antagonist

Answer 9

Aprepitant (use with CS, 5-HT3 antagonist for acute AND delayed CINV)

Question 10

MoA of NK-R antagonist

Answer 10

Act on NK-1 receptor in area postrema of CTZ

Question 11

SE of NK-R antagonist

Answer 11

Fatigue, dizziness, diarrhoea

CYP3A4 metabolism —can be affected by inhibitors such as verapamil, ritonavir

Question 12

Dopamine receptor antagonist

Answer 12

Metoclopramide

Question 13

MoA of Dopa-R antagonist

Answer 13

D2 receptor antagonism blocks CTZ from detecting toxins –> Decreased N&V

Question 14

SE of Dopa-R antagonist

Answer 14

Extrapyramidal SE: restlessness, Parkinsonian Sx especially in elderly
LT use can cause irreversible tardive dyskinesia
Elevated prolactin levels (gynaecomastia, galactorrhoea)

Question 15

Anticholinergics

Answer 15

Hyoscine/Scopolamine

Question 16

MoA of anticholinergics

Answer 16

Act on vestibular system and vomiting centre

Question 17

Use of anticholinergics

Answer 17

PREVENT motion sickness

Question 18

SE of anticholinergics

Answer 18

Typical anticholinergic effect such as urinary retention, dry mouth, BoV
SE can be reduced by transdermal patch than oral

Question 19

Mixed H1 antihistamine, anticholinergic

Answer 19

Diphenhydramine

Question 20

MoA of antihistamine/anticholinergic

Answer 20

H1 and M1 receptor antagonism –> acts on vestibular system and vomiting centre to stop motion sickness

Question 21

Use of antihistamine/anticholinergic

Answer 21

TREAT motion sickness

Due to sedative effect of antihistamine, useful for CINV

Question 22

SE of antihistamine/anticholinergic

Answer 22

Sedation (antihistamine component), anticholinergic effects

Question 23

Antipsychotics

Answer 23

Prochlorperazine (D/Musc/H anta), Droperidol (D/weak H), olanzapine

Question 24

Use of olanzapine

Answer 24

For delayed CINV

Question 25

MoA of antipsychotics

Answer 25

D2 receptor antagonism @ CTZ Musc antagonism @ vestibular system, vomiting centre Weak H1 antagonism

Question 26

SE of antipsychotics

Answer 26

Sedation, EPSE (less with olanzapine), prolonged QT interval (Droperidol)

Question 27

Benzodiazepines

Answer 27

Lorazepam, diazepam

Question 28

MoA of BZD

Answer 28

Bind to allosteric site of GABA receptor --> Cl conductance, potentiate GABA action

Question 29

SE of BZD

Answer 29

Sedation, respiratory depression if OD

Question 30

Contraindication of BZD

Answer 30

Pregnancy (especially 1st trimester due to increased risk of cleft palate)