PHARM_GI Flashcards
How do the bulk forming laxatives work?
increase delivery of water to colon, decrease pressure in sigmoid colon, net result is more formed stools
how does docusate (colace) work?
anionic surfactant, stool softener, used to reduce strain of defecation
what are the adverse effects of docusate (colace)?
can irritate the intestinal mucosa & increase intestinal absorption of other drugs (use only short term)
how does castor oil work?
surfactant laxative that is rapid acting and effective anionic surfactant that produces catharsis, stimulates intestinal peristalsis
what are the AEs of castor oil?
colic
dehydration
electrolyte imbalance with overdose
can induce uterine contraction in pregnant women
on what part of the GI tract do the stimulant laxatives work on?
mostly large bowel
how do stimulant laxatives work?
- increase permeability of intestinal mucosa
- increase back diffusion of water and electrolytes
- increase propulsive contractility of colon by stim. colonic myenteric plexus
- stimulate PG synth. & increase intestinal secretions
what is the most potent class of laxatives?
stimulant laxatives
name the stimulant laxatives
diphenylmethanes (bisacodyl)
anthraquinones (senokot)
bisacodyl (dulcolax) MOA
prodrug that is converted by enteric bacteria into the desacetyl active form, acts as stimulant laxative
anthraquinones (senokot) MOA
stimulant laxative that is natural derivatives of senna plant, more gentle than synthetic drugs
-act by promoting colonic motility
what happens if you overdose on bisacodyl?
can cause excessive fluid & electrolyte loss, intestinal enterocyte damage leading to colonic inflammatory response
large doses of anthraquinones (senokot) can cause what?
can cause abd. pain, nephritis, melanotic pigmentation of colonic mucosa, abnormal color of urine
what is GOLYTELY used for?
Polyethylene glycol electrolyte soln used for colonoscopy for complete evacuation
name the 2 laxatives used in IBS
lubiprostone
linaclotide
how does lubiprostone work?
activates Cl- channels (in PKA independent fashion), increases intestinal fluid secretion and motility and alleviates the symptoms associated with chronic idiopathic constipation (used in IBS for constipation)
what are the 3 different kinds of antidiarrheal agents?
- agents that absorb water (metamucil)
- adsorbers of etiologial factors in the lumen (e.g. pepto-bismol)
- agents that alter intestinal motility (opiates)
how does bismuth subsalicylate work?
adsorb harmful bacteria, viruses, or toxin
what drug is an effective treatment for preventing Traveler’s diarrhea and also treats H. pylori infections?
bismuth subsalicylate
how do opiates work as antidiarrheal agents?
decrease salivary, gastric, & intestinal gland secretions
decrease motility of the stomach & intestines
increase muscle tone
increase tone of muscle sphincters including EAS “reduces urgency”
The overall effect is increasing the contact time between ingested matter and the reabsorbtive intestinal epithelium
this drug interacts with intestinal opioid receptors and binds to & inhibits the calcium binding protein calmodulin
loperamide (anti-diarrheal)
what is the purpose of using anticholinergics as antidiarrheal agents?
used for this b/c they are anti-spasmodic
what drug is prophylactic only for motion sickness arising from short or long exposure to severe motion
scopolamine
scopolamine MOA
scopolamine is anticholinergic that blocks the activation of muscarinic receptors to ACh. (Cochlear sensation of motion is projected via cholinergic fibers of the auditory nerve to the CTZ)
how is scopolamine administered?
patch placed near ear
what are some of the side effects of using scopolamine?
sedation, drowsiness, dry mouth
which antidopaminergic blocks therapeutic induced activation of D2 receptors in the CTZ? Also inhibits gastric emptying
metoclopramide
how do H1 antihistamines work in the treatment of motion sickness?
older H1 antihistamines also have anticholinergic effects
name the 2 piperazines that are H1 antihistamines
cyclizine (OTC)
meclizine
which H1 antihistamine has a depressant effect on hyperstimulation of labyrinthine function and is used for vestibular disturbances?
meclizine
how are antidopaminergics effective antiemetics?
they block dopamine receptors in the trigger zone (CTZ)
which drug is a centrally acting anticholinergic as well as antidopaminergic and is used for N/V & intractable hiccups?
chlorpromazine
which antidopaminergic drug blocks receptors in the CTZ and is clinically used post-op for N/V?
droperidol
which antiemetic antidopaminergic drug is given prophylactically to chemo pts to prevent post-op nausea and vomiting?
metoclopramide
how are serotonin antagonists effective antiemetics?
5-HT antagnoists block 5-HT3 receptors in the stomach and small intestines
-block 5-HT3 receptors in the CTZ that are intimately involved in stimulating the VC to produce emesis
which class of antiemetics are the most effective to date?
5-HT antagonists
which drug is more potent than ondansetron?
granisetron (anti-emetic)
which 5-HT3 antagonist has the longest half life?
dolasetron (anti-emetic)
what is the purpose of using corticosteroids, dronabinol, benzodiazepine or aprepitant, in addition to a classic antiemetic drug?
these 3 are used to increase the potency of antiemetic drugs and reduce the dose of each individual agent and also reduce the significance of their combined side effects
which drug is a substance P/ NK1 receptor antagonist?
aprepitant (anti-emetic)
which drug is used as an adjunct drug for preventing emesis induced by cytotoxic chemotherapy, crosses the BBB & inhibits emesis via central actions
aprepitant (anti-emetic)
which class of drugs is used as an adjunct to other antiemetic regimens and is effective for anticipatory vomiting bc they cause somnolence & amnesia lasting for hours?
benzodiazepines
which class of drugs is considered the foundation for antiemetic therapy?
5-HT3 receptor antagonist
