GI medications Flashcards
Where is the vomiting/emesis center in the brain
medulla oblongata
What does the vomiting/emesis center in the brain do
coordinates contractions of the pharyngeal, GI, and abdominal wall to expel gastric contents
What activates the vomiting center
Afferent fibers in the gut
CTZ
Cerebral cortex
vestibular apparatus
What is CTZ
chemoreceptor trigger zone
What are the chemoreceptors that effect the vomiting center of the brain
Seretonin 5-HT3
Dopamine D2
Muscarinic M1
How does the vestibular apparatus activate the vomiting center of the brain
There are afferent fibers that go into the cerebellum and triggers the release of acetylcholine / histamine
How does the Gut activate the committing center of the brain
There is a vagal afferent pathway to the solitary tract nucleus and then to the vomiting center
There is nerve stimulation of CTZ
D2, 5-HT3 and NK1 receptors
What groups of drugs are used for N/V
Cholinergic/muscarinic antagonist
Dopamine antagonist
seretonin antagonist
Cannabinoids
Histamine antagonists
What drugs for N/V are cholinergic antagonists
Scopolamine (Patch/IV)
What is the MOA of Scopolamine
Blocks acetylcholine at parasympathetic sites and reduces histamine and serotonin activity
What is the PK of scopolamine
Onset 6-8hours
lasts 72 hours
hepatic metabolism
What are the side effects of scopolamine
bradycardia, tachycardia, flushing, orthostatic hypotension, cognitive impairment, psychosis & hallucinations
Which patients cannot use scopolamine
Contraindicated in narrow-angle glaucoma
*or any agents containing belladonna
Which N/V medications are dopamine receptor antagonists
Phenothiazines
Butyrophenones
Benzamides
Which drugs are phenothiazines
Prochlorperazine
Which drugs are Butyrophenones
Haloperidol
Droperidol
Which drugs are benzamides
Metoclopramide
Trimethobenzamide
What is the MOA of dopamine receptor antagonists
Acts on CTZ and afferent pathways primarily in the gut
Does have M1 and Hq blocking effects
*metoclopramide has weak 5-HT3 blockage at higher doses
What are the side effects of dopamine receptor antagonists
Extrapyramidal rxns, QT prolongations, CNS effects, Hyperprolactinemia, tar dive dyskinesia
What major interactions do dopamine agonists have
TCA, SSRI, alcohol, anticholinergics, potassium
Which drugs are serotonin receptor antagonists
Ondansetron
Granisteron
What is the MOA of ondansetron
Blocks seretonin centrally
What are the side effects of Ondansetron
QT prolongation, dizziness, confusion, SOB, constipation
What are things to monitor with ondansetron
EKG monitoring
K+Mg levels
seretonin syndrome
Which drugs does ondansetron interact with
amioderone
QT prolongation drugs
CYP3A4 inducers
Which drugs are QT prolongators
SSRI
Antiarrhythmic agents
tramadol
St. Johns wart
What drugs are cannabinoids
Dronabinol
What are the side effects of cannabinoids
Euphoria, abdominal pain, vomiting, flushing, palpitations, xerostoma, vertigo
What major interactions do cannabinoids have
alcohol, anticholinergics, CNS depressants, CYP3A4 effectors, metronidazole, disulfiram, warfarin
What drugs are histamine antagonists
Promethazine
Meclizine
Dimenhydrinate
What is the MOA of Promethazine
Blocks the mesolimbic dopaminergic receptors in postsynaptic sites
blocks the release of hormones from the hypothalamus
blocks H1 in brainstem
What serious issue is associated with injectible promethazine
Tissue injury with extrav
What is the MOA of meclizine
Block H1 and prevents vasodilation, bronchoconstriction, and spasmodic contraction of GI smooth muscle
*may effect CTZ
What are the side effects of meclizine
Sedation
headaches
vomiting
blurred vision
Which patients should not receive meclizine
glaucoma
asthma
urinary retention
pyloric/duodenal obstruction
What does meclizine have major interactions with
alcohol
amphetamines
anticholinergics
nitro
K