nausea pharmacology

Question 1

what can stimulate the vomit reflex

Answer 1

gag reflex
noxious chemicals - CTZ
mechano/chemo-receptors in the stomach or duodenum
rotation of the head - vestibular nuclei
elevated intracranial haemorrhage
emotion

Question 2

what is the CTZ/AP

Answer 2

no BBB
samples blood for noxious chemicals
nucleus of the solitary tract project into CTZ - coordinates motor side of vomiting reflex

Question 3

how can the GIT cause N&V

Answer 3

• Chemoreceptors on enterochromaffin cells detect noxious chemicals, mechanoreceptors detect stretch
• Release 5HT which stimulates nerve endings of vagal afferents
• 5-TH is also released into the systemic circulation, which then gets to CTZ via blood stream

Question 4

what are the two steps of motor output in the vomiting reflex

Answer 4

autonomic
somatomotor

Question 5

what are the steps in the autonomic response to vomiting

Answer 5

increased salivation
sweating
cutaneous vasoconstriction
increased HR
small intestine contraction
stomach, oesophageal, sphincter relaxation

Question 6

what are the steps in the somatomotor response to vomiting

Answer 6

diaphragm contraction
nasal passage and airway closure
Strong diaphragm contraction and abdominal muscles

Question 7

what role does acetylcholine play in nausea and vomiting

Answer 7

muscarinic receptors in the vestibular system

Question 8

what role does histamine play in nausea and vomiting

Answer 8

acts in vestibular and nts

Question 9

what role does 5HT play in nausea and vomiting

Answer 9

acts in the AP and centrally - central and peripheral effects

Question 10

what role does substance p play in nausea and vomiting

Answer 10

activates NK receptors in the gut and NTS

Question 11

what role does endocannabinoids play in nausea and vomiting

Answer 11

CB1 receptor activation - emetic

Question 12

what role does enkephalins play in nausea and vomiting

Answer 12

inhibiting can cause N&V, activating can inhibit

Question 13

what are muscarinic antagonists and how are they used in the treatment of nausea and vomiting

Answer 13

• hyoscine
  motion sickness - crosses BBB

Question 14

what are H1 antagonists and how are they used in the treatment of N&V

Answer 14

• cinnarizine, cyclizine and promethazine
  used for lots of causes - drowsy and anti-muscarinic s/e

Question 15

what are 5HT3 antagonists and how are they used in the treatment of N&V

Answer 15

• ondansetron
  post op/chemo/radio
  can cause Qt prolongation

Question 16

what are D2 antagonists and how are they used in the treatment of nausea and vomiting

Answer 16

provhlorperazine - antipsychotic (H1, muscarinic, D2)
metoclopramide - direct action on GIT
domperidone - does not cross BBB

Question 17

what are NK1 antagonists and how are they used in the treatment of N&V

Answer 17

aprepitant - adjunct
blocks substance P

Question 18

what are CB1 agonists and how are they used to treat N&V

Answer 18

nabilone - blocked by naloxone
chemo
drowsiness and psychosis

Question 19

how are corticosteroids used in the treatment of N&V

Answer 19

dexamethasone in chemotherapy