GI - emesis

Question 1

what is emesis

Answer 1

forceful evacuation of gastric contents through mouth

Question 2

what are 3 reasons for vomiting

Answer 2

physiological response to: irritating substances in gut/blood, excessive vestibular stimulation (motion sickness), physiological stimuli (fear, odours)

Question 3

what is nausea

Answer 3

feeling of impending vomiting

Question 4

are all anti emetics anti nauseant

Answer 4

no, most arent

Question 5

is nausea or vomiting harder to control pharmacologically

Answer 5

nausea

Question 6

what are emetic drugs / what do they do + why do we use them

Answer 6

induce vomiting to prevent absorption of ingested toxic substances

Question 7

what is ipecac

Answer 7

emetic drug

Question 8

why is vomiting bad in lots of treatments

Answer 8

it reduces effectiveness by causing dehydration of nutrient depletion

Question 9

where is vomiting regulated

Answer 9

centrally by medulla

Question 10

what is the chemoreceptor trigger zone

Answer 10

BBB near the CTZ is relatively permeable, allowing circulating emetogenic mediators to act, communicates to vomiting center

Question 11

what kind of inputs does the chemoreceptor trigger zone receive / where from

Answer 11

vestibular nuclei and directly from GI tract

and of course the circulating substances in blood by the zone too

Question 12

where is the chemoreceptor trigger zone located

Answer 12

in the area postrema

Question 13

what is the difference between chemoreceptor trigger zone and area postrema

Answer 13

The CTZ is located within the area postrema

Question 14

what is the vomiting center (what happens here) (where are impulses received from)

Answer 14

impulses from CTZ, GI tract and higher cortical centers, coordinate physical act of vomiting

Question 15

what is the vestibular nuclei

Answer 15

imputs from inner ear, it is responsible for dizziness and nausea

Question 16

what are the 3 main components in the vomiting reflex

Answer 16

chemoreceptor trigger zone, vomiting center, vestibular nuclei

Question 17

what are the roles of higher cortical centers in vomiting

Answer 17

reaction to pain, repulsive sights, smells, emotional factors

Question 18

what is the role of vagal afferents in vomiting

Answer 18

convey signals from gut to brainstem

Question 19

what is the main site for sensing emetic stimuli

Answer 19

chemoreceptor trigger zone

Question 20

what do enterochromaffin cells have to do with the vomiting reflex

Answer 20

they sense toxic chemicals or toxins in the gut

Question 21

what is the mechanism of muscarinic receptor antagonists as anti emetics

Answer 21

selective, competitive antagonists at the vomiting center & vestibular nuclei

Question 22

when do you use muscarinic receptor antagonists

Answer 22

prophylactically for motion sickness and post op emesis

Question 23

what are the side effects of muscarinic receptor antagonists

Answer 23

dry mouth, blurred vision, sedation, constipation

Question 24

what is an example of a muscarinic receptor antagonists

Answer 24

hyoscine

Question 25

what is hyoscine

Answer 25

muscarinic receptor antagonists

Question 26

what is the mechanism of action of 5HT3 receptor antagonists

Answer 26

selective, competitive, act at CTZ and visceral afferents

Question 27

what example of a drug is a 5HT3 receptor antagonist

Answer 27

ondansetron

Question 28

what is ondansetron

Answer 28

5HT3 receptor antagonist

Question 29

when do they like to use 5HT3 receptor antagonist

Answer 29

chemotherapy-induced emesis

Question 30

how do chemo agents cause emesis

Answer 30

they release 5HT from enterochromaffin cells & directly stimulate CTZ and visceral nerves

Question 31

is ondansetron good for motion sickness

Answer 31

no not effective

Question 32

what is a bad thing about ondansetron

Answer 32

it can cause long QT syndrome

Question 33

what is the mechanism of D2 receptor antagonists

Answer 33

selective, competitive, antagonist in the CTZ

Question 34

what are 2 examples of D2 receptor antagonists

Answer 34

metoclopramide and domperidone

Question 35

what is metoclopramide

Answer 35

D2 receptor antagonists

Question 36

what is domperidone

Answer 36

D2 receptor antagonists

Question 37

what is the difference with domperidone and metoclopramide

Answer 37

metoclopramide crosses BBB, domperidone doesnt

Question 38

how does metoclopramide compare to ondansetron

Answer 38

its not as good for chemitherapy vomiting

Question 39

what are 2 uses for metoclopramide

Answer 39

chemo-induced vomiting and increasing GI motility

Question 40

what is a bad thing about metoclopramide

Answer 40

it crosses BBB so it can cause movement disorders

Question 41

does metoclopramide cross the BBB

Answer 41

yes

Question 42

does domperidone cross the BBB

Answer 42

no

Question 43

does domperidone increase gut motility

Answer 43

yes

Question 44

does metoclopramide increase gut motility

Answer 44

yes

Question 45

what are 4 other anti emetics (besides D2 5HT3 and musc antagonists)

Answer 45

antipsychotic phenothiazines, cannabinoids, glucocorticoids, NK1 receptor antagonists

Question 46

what do we use antipsychotic phenothiazines for

Answer 46

treatment of more severe nausea and vomiting associated with cancer, radiation therapy, cytotoxic drugs, opioids, anesthetics, etc

Question 47

what is the mechanism of action of antipsychotic phenothiazines

Answer 47

D2 receptor antagonists: act in CTZ, but can also block histamine and muscarinic receptors

Question 48

why dont we use antipsychotic phenothiazines a lot

Answer 48

because of unwanted effects

Question 49

what is the mechanism of cannabiniods in anti-emesis

Answer 49

act in CTZ

Question 50

what is the mechanism of glucocorticoids in anti-emesis

Answer 50

unknown

Question 51

when are glucocorticoids used for nausea

Answer 51

with chemo

Question 52

what is the mechanism of NK1 receptor antagonists in anti-emesis

Answer 52

action at CTZ and vomiting center

Question 53

when do you use NK1 receptor antagonists

Answer 53

with chemo induced vomiting, combo with glucocorticoids