GI Flashcards
Scopolamine is a
Cholinergic Antagonist
Scopolamine can come in what forms?
patch and injectable
Scopolamine mechanism of action
Blocks the acetylcholine at parasympathetic sites (smooth muscle, secretary glands, CNS)
Reduces histamine and serotonin activity
Scopolamine onset and duration
onset - 6-8 hours
duration - 72 hours
Scopolamine side effects
similar effect to atropine - bradycardia then tachycardia, flushing, orthostatic hypotension, cognitive impairment, psychosis and hallucinations
Scopolamine is contraindicated in
narrow angle glaucoma
Phenothiazines
Butyrophenones
Benzamides are all
Dopamine receptor antagonists
Phenothiazine include
Prochlorperazine
Butyrophenones include
Haloperidol
Droperidol
Benzamides include
Metoclopramide
Thrimethobenzamide
MOA for Dopamine receptor antagonists
acts primarily on the CTZ and afferent pathways in the gut
Antagonize D2 dopamine receptors in area postrema and peripheral sites
M1-muscarinic and H1-histamine blocking effects
Metoclopramide has weak 5-HT3 blockage at higher doses
Side effects of Dopamine receptor antagonists
Extrapyramidal reactions (Dystonia), tardive dyskinesia, QT prolongation, CNS/psych effects, hyperprolactinemia, Hypotension
Prochlorperazine onset and duration
onset - PO = 30-40 min
rectal approximately 60 min
Duration = 3-4 hours oral, 3-12 rectal
Metoclopramide duration
1-2 hours
Ondansetron and Granisetron are
Serotonin receptor antagonists
Ondansetron MOA
Blocks serotonin centrally and peripherally
Ondansetron onset and peak
onset = approx 30 min
peak = 1-2 hours
Ondansetron side effects
QT prolongation, dizziness, confusion, SOB, constipation
Ondansetron major interactions
amiodarone
QT prolonging agents
CYP3A4
Cannabinoids MOA
activates cannabinoid receptors
Cannabinoids onset, peak, duration
onset - 30-60 min
peak - 2-4 hours
duration - 4-6 hours
Cannabinoids side effects
euphoria
CNS changes
abdominal pain
vomiting
flushing
palpitations
hypotension
xerostomia
vertigo
Promethazine
Meclizine
Dimenhydrinate
Histamine antagonists
Promethazine MOA
blocks mesolimbic dopaminergic receptors in postsynaptic sites
Blocks the release of hormones from the hypothalamus
Blocks histamine 1 receptors in the brainstem
Promethazine Onset and duration
onset - IV ~5 min, PO/IM ~ 20 min
duration - 4-6 hours
Promethazine Side effects
EKG changes, anticholinergic effects, CNS depression, orthostatic hypotension
Meclizine MOA
Blocks HI histamine receptor and prevents vasodilation, increased capillary permeability, bronchoconstriction and spasmodic contraction of GI smooth muscles
depresses labyrinth excitability and vestibular stimulation
Meclizine onset and duration
onset - 1 hour
duration - ~24 hours
Meclizine side effects
sedation
HA
vomiting
blurred vision
Meclizine avoid in
glaucoma, asthma, urinary retention, or pyloric/duodenal obstruction
Dimenhydrinate MOA
binds to H1 receptor sites in peripheral sites including GI tract, resp tract, and blood vessels
blocks chemoreceptor trigger zones
Depresses labyrinthine function and vestibular stimulation
Central anticholinergic activity
Dimenhydrinate onset and duration
onset = up to 30 min for IM and PO
duration = 4-6 hours
Dimenhydrinate rarely causes
SJS
Dimenhydrinate do not use with
abx that are known to cause ototoxicity
Opioid Agonists
Serotonin receptor modulators
bile acid sequestrants
anti-spasmodics
antimicrobial agents
Can all be used for
Diarrhea and IBS-D
MOA Opioid Agonists
Activation of opioid receptors in the smooth muscle of the GI tract. Alters peristalsis by preventing smooth muscle contraction and relaxation. Reduces stool volume and can prevent electrolyte depletion
before using opioid agonists you should correct any
fluid/electrolyte imbalances
Do not use opioid agonists with
infectious diarrhea/toxic megacolon
Loperamide
Diphenoxylate/Atropine
Octreotide
Eluxadoline are all
opioid compound drugs
MOA Loperamide
also increases IAS and EAS tone
Diphenoxylate/ atropine - why does it contain atropine
contains small amount of atropine to prevent abuse
Octreotide MOA
Inhibits serotonin release
inhibits secretion of gastrin, VIP, insulin, glucagon, secretin, motilin and pancreatic polypeptide
MOA Eluxadoline
Binds to mu, kappa and delta opioid receptors in the intestinal lumen
decreases intestinal motility without causing constipation
Eluxadoline considerations
can cause acute pancreatitis in pts with cholecystectomy
Do not give to pts with EtOH abuse
do not use in pts with h/o intestinal obstruction
can cause CNS depression
Alosetron
Tegaserod are
serotonin receptor modulators
Alosetron is used for
chronic >6 months severe IBS-D
Alosetron MOA
selective 5-HT3 agonist
acts on receptors in the enteric neurons in addition to receptors in other locations centrally and peripherally
affects visceral pain, colonic transit, and alters secretions in the GI tract
Alosetron can rarely cause
ischemic colitis
do not use in pts with h/o GI obstruction, crohns, diverticulitis, vasculopathy, thrombophlebitis, hypercoagulable conditions