Antiemetics

Question 1

Why do we vomit

Answer 1

Protective mechanism, eliminate irritant/harmful substances from upper GIT

Question 2

What triggers vomiting

Answer 2

Afferent impulses to the vomiting center in the medulla

Question 3

Where does the vomiting centre send impulses to

Answer 3

Efferent impulses to the salivation centre, respiratory centre and pharyngeal/GI/abdominal muscles leading to vomiting

Question 4

Pathophysiology of vomiting

Answer 4

Nausea, upper small intestine contracts, emptying of upper jejunum, duodenum and pyloric portion of the stomach into the stomach, pyloric sphincter contract, LES, oesophagus and upper oesophageal sphincter relax, deep sharp inspiration, closure of glottis and raising of soft palate, abdominal muscles contract rhythmically, stomach compressed between contract diaphragm and abdominal organs

Question 5

What are the phases of emesis

Answer 5

Nausea and excess autonomic activity, retching, expulsion

Question 6

What happens during nausea

Answer 6

Sweating, salivation and pallor

Question 7

What happens during retching

Answer 7

Closure of glottis, cessation of respiration, contraction of diaphragm and abdominal muscles

Question 8

What happens during expulsion

Answer 8

Gastric contents expelled, relaxation of lower oesophageal sphincter, contraction of abdominal muscles

Question 9

Vomiting neurotransmitters

Answer 9

Ach, histamine, dopamine and 5-HT

Question 10

Emesis triggers

Answer 10

Pain, repulsive sights/smells/tastes, emotional factors, motion sickness, pregnancy, stimuli of intramucosal sensory nerve endings, endogenous toxins, drugs, radiation therapy

Question 11

What affects anti-emetic drug selection

Answer 11

Severity, route of administration, age

Question 12

H1 receptor antagonists

Answer 12

Cyclizine, doxylamine, dimenhydrinate, promethazine, pheniramine

Question 13

What are H1 receptor antagonists mainly used for

Answer 13

Relief of vestibular disorders

Question 14

Antimuscarinics

Answer 14

Hyoscine hydrobromide

Question 15

Side effects of antimuscarinics

Answer 15

Anticholinergic

Question 16

Use of antimuscarinics

Answer 16

Motion sickness prophylaxis 30 mins before travel

Question 17

5HT-3 receptor antagonists

Answer 17

Granisetron, ondansetron, palonosetron, tropisetron

Question 18

Common uses of 5HT-3 receptor antagonists

Answer 18

Prevent and treat nauseas and vomiting following chemo, radiation or surgery

Question 19

Common adverse effects of 5HT-3 receptor antagonists

Answer 19

Constipation, headache, dizziness, transient elevation of liver enzymes

Question 20

D2 receptor antagonists

Answer 20

Domperidone, droperidol, haloperidol, metoclopramide, prochlorperazine

Question 21

Side effects of D2 receptor antagonists

Answer 21

Extrapyramidal side effects (tremor, slurred speech, akathisia, dystonia, anxiety, paranoia)

Question 22

Extra activity of domperidone and metoclopramide

Answer 22

Prokinetic activity (enhance gastric emptying and intestinal motility), useful for nausea and vomiting caused by gastroparesis

Question 23

Side effects of domperidone

Answer 23

Dry mouth, headache, prolong QT interval, hyperprolactinaemia leading to galactorrhoea and gynaecomastia

Question 24

Dosage form of droperidol

Answer 24

IM or IV injections

Question 25

Side effects of droperidol

Answer 25

Sedation

Question 26

Use of metoclopramide

Answer 26

Nausea and vomiting in general and those associated with migraines

Question 27

Side effects of metoclopramide

Answer 27

Worsen mental state, tardive dyskinesia (worsen symptoms of Parkinsons, prochlorperazine similar affect)

Question 28

Substance P antagonists

Answer 28

Aprepitant (oral) and fosaprepitant (IV), netupitant only in combo with palonosetron

Question 29

Use of substance P antagonists

Answer 29

Chemo induced nausea and vomiting in combo with other agents

Question 30

Adverse effects of substance P antagonists

Answer 30

Diarrhoea, fatigue, headache, dizziness, weakness, hiccups, increased hepatic enzymes, induce CYP3A4 (reduce effects of contraception)

Question 31

Dexamethasone as an anti-emetic

Answer 31

Act synergistically with 5HT-3 receptor antagonists to potentiate anti-emetic effect

Question 32

What is dexamethasone used for

Answer 32

Prevent PONV and chemo induced nausea and vomiting in conjunction with other anti-emetics

Question 33

Why do benzodiazepines work as adjunct Tx

Answer 33

Anxiolytic and sedative effects

Question 34

How do cannabinoids work as anti-emetics

Answer 34

Decrease vomiting by agents that stimulate the CTZ

Question 35

What cannabinoids are used as anti-emetics

Answer 35

Dronabinol and nabilone for chemo induced vomiting not controlled by conventional anti-emetics

Question 36

Non-pharmacological therapy for vomiting in pregnancy

Answer 36

Maintain hydration, avoid trigger foods, adjust diet portions

Question 37

First choice for anti-emetics in pregnancy

Answer 37

Ginger up to 1g daily or pyridoxine 25-50mg up to tds

Question 38

2nd line for anti-emetics in pregnancy

Answer 38

If first line ineffective use doxylamine, metoclopramide, promethazine or prochlorperazine

Question 39

What is hyperemesis gravidarum

Answer 39

Extreme and persistent nausea during pregnancy, can lead to dehydration

Question 40

Non pharm measures for hyperemesis gravidarum

Answer 40

Lifestyle adjustments and IV rehydration

Question 41

Drug therapy for hyperemesis gravidarum

Answer 41

Metoclopramide, prochlorperazine or ondansetron

Question 42

What is PONV

Answer 42

Post operative nausea and vomiting

Question 43

Drugs effective in PONV

Answer 43

Cyclizine, droperidol, dexamethasone

Question 44

Benefits and downsides for droperidol in PONV

Answer 44

Long acting, counteracts opioid adverse effects, sedation

Question 45

What anti-emetics should be given before anaesthesia

Answer 45

Palonosetron and dexamethasone