pharmacology of nausea and vomiting Flashcards
how is vomiting induced
toxic materials and toxins stimulate enterochromaffin cells in the mucosa which release mediators eg serotonin.
there is depolarisation of sensory afferent terminals in the mucosa and AP discharge in vagal afferents to brainstem
what are the sphincters like during vomiting
relaxed
name 3 prodromal signs
skin - pallor and cold sweat
heart - inc rate and force
salivary glands - inc secretion
what effect does vomiting have on K
hypokalaemia
how do dopamine antagonists work
block the CTZ
what are dopamine antagonists used for
associated radiation sickness, drug induced emesis and neoplastic disease
how are dopamine antagonists available
rectal suppositories and buccal
name 2 prokinetic drugs
metoclopramide and domperidone
what is metoclopramide also used in
migraine - inc the absorption of other drugs
what does domperidone not cross
the BBB
what are 5HT3 antagonists used in
CINV, radiation induced and PONV
what is a side effect of 5HT3 antagonists
headache
what are H1 antihistamines used in
motion sickness, morning sickness and PONV
what is cinnarzine also used for
additional antivertigo action inhibiting calcium influx & suppressing labyrinthine reflexes, thus helping in tinnitus and Ménière’s disease.
anticholingerics
hyoscine and dicyclomine
how can anticholingerics be used
transdermal patch, oral, IM
what are the side effects of anticholingerics
blurred vision, urinary retention, dry mouth and sedation
what are anticholingerics used in
motion sickness
what is the triple drug regime used in CINV
5HT3 receptor antagonist and dexamethasone and aprepitant
what is dexamethasone
corticosteroid
acute CINV
pretreatment with dexamethasone, lorazepam and triple regime
delayed CINV
triple regime and metoclopramide
anticipatory CINV
lorazepam
what are some non pharmacological treatment s for pregnancy associated nausea and vomiting
changes in diet ginger or pyridoxine wrist acupressure (P6)
what is Hyperemesis gravidarum
fluid and electrolyte disturbances or nutritional deficiency that develops from intractable vomiting in pregnancy.
first line for Hyperemesis gravidarum
antihistamine - promethazine or cyclizine
second line for Hyperemesis gravidarum
prochlorperazine and metoclopramide.
what is the gastroileal reflex stimulated by
gastric distension
what does the gastroileal reflex involve
opening of the ileocaecal valve
what does teh large intestine secrete
K, HCO3 and mucus
what is haustration
Non propulsive segementation caused by contraction of the circular muscle
what does haustration allo
time for fluid and electrolyte reabsorption
what is the role of the colonic flora
promote motility and help maintain mucosal integrity
synthesise vitamin K2 and free fatty acids (from carbohydrate) that are absorbed
activate some drugs
what is Sulfasalazine
5-ASA linked to sulfapyridine by an azo bond
how does Sulfasalazine work
reduces inflammation by inhibiting COX and LOX
Sulfasalazine AE
include rashes, arthralgias, blood dyscrasias
what are Sulfasalazine AE due to
absorbed sulfapyridine
what is advised durin the use of Sulfasalazine
folic acid
what is better tolerated than Sulfasalazine
mesalazine
what is balsalazide
a prodrug
how do IS work
inhibit T lymphocyte function
what is the AE of ciclosprin
renal toxicity
what is 6-Mercaptopurine
a metabolite of azathioprine
what is 6-Mercaptopurine
used for
maintenance of remission of IBD
what is given in IBS
antispasmodic
laxative
antimotility
antidepressant
what is the first line antimotility in IBS
loperamide
what laxative would you not give in IBS
lactulose
what is the value of antispasmodics in IBS
relieve cramps
what are some direct SM relaxants
Alverine, mebeverine, peppermint oil
what is the effect of antidepressants in IBS
prevent afferents from GIT/reduce pain perceptions
name some selective serotonin uptake inhibitors
Citalopram, Fluoxetine, Paroxetine
what is diarrhoea defined as
loss of fluid and solutes from the GI tract > 500ml per day
