Nausea, vomiting & electrolyte balance Flashcards
Where does central regulation of vomiting occur?
vomiting centre & the chemoreceptor zone CTZ
Where do anti - emetic drugs work?
CTZ
How is vomiting initiated?
output from CTZ stimulates vomiting centre
What are the 4 NTs involved in nausea & vomiting?
Histamine, ACh, dopamine, 5-HT
H1 antagonist helps which kind of sickness? give an example of a drug used and a side effect
motion sickness
promethazine - drowsiness
How does anti -muscarinics help sickness, give two examples and side effects
motion sickness also reduce gastric motility
hyoscine, prochlorperazine
anti muscarinic side effects and drowsiness
How do dopamine antagonists work, give 2 examples and a side effect
act on CTZ, good against anti cancer drug induced emesis
stimulates gastric emptying
CNS side effects
domperidone, metoclopramide
How do 5-HT antagonists work, give an example
blocks 5-HT at 5-HT3 receptors in gut & CNS good against anti cancer drug
What are neurokinin receptor antagonists and how do they work? give an example
NK1 receptor activated by substance P
NK1 antagonist suppress nausea and vomiting
Aprepitant
What other drugs have anti - emetic effects?
steriods - dexamthasone
What electrolytes are losses during vomiting?
H+, k+ and water
What electrolytes are losses during diarrhoea? what does this cause?
Na+ and water
dehydration, reduced BP, muscle weakness, reduced level of consciousness, heart failure, convulsions
Na+ and water excretion from kidney is regulated by which hormones?
vasopressin & aldosterone
What is acidosis and what happens during this?
pH decreases causing H+ to enter cell forcing k+ out of cells (hyoerkalemia)
What is alkalosis?
pH increases so K+ enters cells hypo
