nausea and emesis

Question 1

where is the chemo receptor trigger zone (CTZ) located and what does it do?

Answer 1

outside of BBB, senses what is going on in the blood
recognises emetic agents (toxins, drugs)

Question 2

where is the vomiting centre located and what does it control?

Answer 2

in medulla oblongata - fourth ventricle
induces act of vomiting from pain, smells, motion

Question 3

what inputs does the NTS (nucleus tractus solitaris) receive?

Answer 3

pharyngeal stimulation
gastric distention/irritation

Question 4

what does the vomiting centre coordinate vomiting through?

Answer 4

interactions with cranial nerves 8 and 10
neural networks in NTS

Question 5

what receptors are found in high concentrations in VC?

Answer 5

M1, H1, NK1, 5-HT3

Question 6

what kind of nausea and vomiting is vestibular system responsible for?

Answer 6

motion and morning sickness

Question 7

what kind of nausea and vomiting is CTZ responsible for?

Answer 7

chemotherapy induced
opioid induced

Question 8

causes of nausea and vomiting?

Answer 8

infections
drugs
GI disease
pregnancy
increase in Ca2+

Question 9

consequences of N+V?

Answer 9

dehydration
malnutrition
acid-base balance
aspirational pneumonia
oesophageal tear

Question 10

what antiemetics are primarily used for treatment of pregnancy, PONV and motion sickness?

Answer 10

antihistamines
anticholinergics

Question 11

what antihistamines are used for N+V?

Answer 11

H1 receptor antagonists
cyclizine, promethazine, diphenhydramine

Question 12

how do antihistamines work to treat N+V?

Answer 12

block H1 receptors in vestibular nuclei
can exert blockade of muscarinic receptors

Question 13

side effects of antihistamine use for N+V?

Answer 13

drowsiness - CNS depression/sedation
blurred vision
constipation, urinary retention

Question 14

what anticholinergics are used for N+V?

Answer 14

muscarinic acetylcholine receptor antagonists
hyoscine hydrobromide

Question 15

how do anticholinergics work to treat N+V?

Answer 15

block receptors at multiple sites
direct inhibition of GI movement and relaxation of GI tract contribute to antiemetic effect

Question 16

side effects of anticholinergics?

Answer 16

unwanted effects resulting from blocking of parasympathetic ANS - dry mouth, constipation, blurred vision
centrally-mediated sedation

Question 17

examples of dopamine antagonists used?

Answer 17

haloperidol, prochlorperazine, domperidone

Question 18

mechanism of action of dopamine antagonists?

Answer 18

centrally block D2 receptors in CTZ
peripherally exert prokinetic action on oesophagus stomach and intestines

Question 19

why is domperidone less likely to result in unwanted effects of metoclopramide?

Answer 19

does not cross BBB

Question 20

what kind of vomiting are dopamine antagonists used for?

Answer 20

drug-induced vomiting
vomiting in GI disorders

Question 21

examples of serotonin 5HT3 receptor antagonists?

Answer 21

ondansetron, granisetron, palonsetron

Question 22

side effects of serotonin receptor antagonists?

Answer 22

constipation, headache

Question 23

clinical considerations of serotonin receptor antagonists?

Answer 23

single dose same efficacy as multidose regimens
Oral and IV routes equivalent