anti emetics

Question 1

how and where is emesis controlled?

Answer 1

controlled and centralised by brainstem in a nautral network on dorsal surface of medulla - referred to as the “brainstem emetic control centre” or dorsal vagal complex

Question 2

what is the vomiting reflex regulated by?

Answer 2

CNS (medulla)

Question 3

what is the main site of action for ant-emetic drugs?

Answer 3

chemoreceptor triggering zone (CTZ)

Question 4

what is the CTZ physically associated with?

Answer 4

emetic centre

Question 5

which side of the blood brain barrier is CTZ located?

Answer 5

blood side

Question 6

what is the target for anti-emetic drugs?

Answer 6

blockade of neurotransmitters involved in triggering emesis

Question 7

name the 6 endogenous neurotransmitters involved in triggering emesis

Answer 7

serotonin
AcH
Dopamine
Substance P
Histamine
Enkephalin

Question 8

name the various pathways involved in stimulating the vomiting centre

Answer 8

vestibular pathway
vagal pathway
CTZ and emetic centre

Question 9

what stimulates the vestibular pathway?

Answer 9

disorientating movement

Question 10

what stimulates the vagal pathway?

Answer 10

sensory input (pain, smell, sight, thought)
stimuli from pharynx
stimuli from GI tract

Question 11

what stimulates the CTZ and emetic centre?

Answer 11

endogenous substances
toxins
drugs

Question 12

name 7 classes of anti emetics

Answer 12

H1 histamine antagonists
muscarinic receptor antagonists
D2 Dopamine antagonists
5HT3 serotonin antagonists
NK1R neurokinin -1 antagonists
cannabinoids
corticosteriods

Question 13

name 3 H1 (histamine) antagonists

Answer 13

cyclizine
cinnarizine
promethazine

Question 14

what is the mechanism of action of H1 (histamine) antagonists and in which areas to they act ?

Answer 14

blocks H1 (histamine) receptors on vestibular pathway and vomiting centre

Question 15

what are type of emesis are H1 (histamine) antagonists used to treat?

Answer 15

cyclizine - motion sickness
cinnarizine - motion / vestibular disorders
promethazine - severe morning sickness

Question 16

what are the side effects of H1 (histamine) antagonists?

Answer 16

drowsiness

sedation (contributes to efficacy)

Question 17

name 2 muscarinic receptor agonists used as anti-emetics

Answer 17

hyoscine

scopolaine

Question 18

what is the mechanism of action of muscarinic receptor agonists and in which areas to they act ?

Answer 18

block muscarinic receptors in vestibular pathway and vomiting centre
block neurotransmitter Ach

Question 19

what are type of emesis are muscarinic receptor antagonists used to treat?

Answer 19

general purpose
motion sickness (drug of choice)

Question 20

what are the side effects of muscarinic receptor antagonists?

Answer 20

dry mouth
blurred vision
less sedation (than antihistamines)

Question 21

name 5 dopamine antagonists

Answer 21

phenothiazides
prochlorpromine
perphenazine
metaclopromide
domperidone

Question 22

what is the mechanism of action of dopamine anatagonists?

Answer 22

block dopamine receptors - strong representation in CTZ

also antagonise M and H receptors

Question 23

what type of emesis are phenothiazides, prochlorpromine and perphenazine used to treat?

Answer 23

uremia
opiod induced emesis
CINV
GI disorders
viral gastro enteritis

Question 24

what are the side effects of phenothiazides, prochlorpromine and perphenazine?

Answer 24

sedative
hypotension
dystonia
dykinesia

Question 25

which body system does metaclopromide act on?

Answer 25

GIT, increase GI motility

Question 26

what are the side effects of metaclopromide?

Answer 26

movement disorders fatigue motor restlessness etc. penetrates BBB

Question 27

what is domperidone used to treat?

Answer 27

migraine cytotoxic induced therapy emesis emergency contraceptive sickness does not penetrate BBB - few SE

Question 28

name four 5HT3 serotonin antagonists

Answer 28

ondanstron granistron palonosetron tropisetron

Question 29

what is the mechanism of action for 5HT3 serotonin antagonists?

Answer 29

blocks serotonin receptors in CTZ, vomiting centre and vagal pathway

Question 30

what is the drug of choice for CINV and PONV?

Answer 30

ondanstron

Question 31

what are the side effects of 5HT3 serotonin antagonists?

Answer 31

GI disterbances | headache

Question 32

name three NK1R neurokinin-1 antagonists?

Answer 32

``` aprepitant fos aprepitant (PRODRUG) maprepitant ```

Question 33

what is the mechanism of action for NK1R neurokinin-1 antagonists?

Answer 33

antagonists substance P

Question 34

what is NK1R neurokinin-1 antagonists used for?

Answer 34

CINV and PONV

Question 35

what are the side effects of NK1R neurokinin-1 antagonists?

Answer 35

``` fatigue listlessness constipation/ diahorrea loss of appetite hiccups ```

Question 36

name 2 cannabinoids

Answer 36

nabilone | marinol

Question 37

what is the mechanism of act of cannabinoids?

Answer 37

agonist cannabinoid receptors | act via opioid receptors in CTZ

Question 38

what are cannabinoids used to treat?

Answer 38

CINV

Question 39

what are the side effects of cannabinoids?

Answer 39

``` drowsiness dizziness dry mouth mood changes postural hypotension ```

Question 40

which corticosteroid is used as an anti-emetic and which type of emesis is it used for?

Answer 40

dexamethosone | cytotoxic drugs - used in combo with D2 or 5HT3 antagonist for improved action