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GI and liver > GI protectants > Flashcards

GI protectants Flashcards

1
Q

two major classes of drugs affecting GI system

A

drugs affecting secretion: antacids, H2 histamine receptor antagonists, PPIs
drugs affecting GI motility: prokineic, anti-diarrheal/emetic

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2
Q

drugs affecting GI secretions are used in the treatment of:

A

peptic ulcers (gastric or duodenal), GERD, and hypersecretory states such as zollinger-ellison syndrome

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3
Q

physiologic control of GI secretions

A

vary depending on the area where the cell is located
secretions controlled by many receptors and singals (histamine, ACh, gastrin) - lead to activation of proton pumps and acid pumped into stomach

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4
Q

ulcer

A

a failure of mucosal protection

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5
Q

antacids

A

NaHCO3, CaCO3, Al(OH)3, Mg(OH)2

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6
Q

NaHCO3

A

high neutralizing capacity

AEs: systemic alkalosis, fluid retention

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7
Q

CaCO3

A

moderate neutralizing capacity

AEs: hypercalcemia, nephrolithiasis, milk-alkali syndrome

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8
Q

Al(OH)3

A

high neutralizing capacity

AEs: constipation**, hypophosphatemia

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9
Q

Mg(OH)2

A

high neutralizing capacity

AEs: diarrhea**, hypermagesemia

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10
Q

commercial antacids

A

alternagel - Al(OH)3
maalox, mylanta - Al(OH)3 and Mg(OH)2
tums - CaCO3
gaviscon (sodium alginate + antacids) - viscous, weak base, prevents reflux, effective in GERD

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11
Q

1st generation H2 receptor antagonist

A

cimetidine
competitive antagonist
reduce gastric acid secretion in response to histamine, gastrin, ACh
inhibits CYP 2C6 and 2D9: warfarin, phenytoin, theophylline, benzos, sulfonylureas
SE: CNS effects (delerium) with IV adin to elderly, antiandrogen (gynecomastia, impotence), inhibition of estradiol metabolism (galactorhhea), thrombocytopenia

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12
Q

2nd gen. H2 receptor antagonists

A

ranitidine, nizatidine, famotidine
competitive antagonist of H2 histamine receptor
reduce gastric acid secretion in response to histamine, gastrin, ACh
longer half life than 1st gen
increase ethanol bioavailability by reducing first-pass meabolism (not famotidine)
fewer effects on CYP
greater potency

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13
Q

PPI examples and actions

A

esomeprazole, lansoprazole, rabeprazole, pantoprazole
actions:
prodrugs: activated by acid
irreversible inhibitor of H+/K+ATPase
short t1/2 but long duration of action* due to covalent inhibition
hypergastremia occurs and may result in rebound hyper secretion of gastric acid upon withdrawal
inc in gastric pH can affect drug absorption and potentially increase risk of infections

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14
Q

PPI AEs

A

few, nausea most common, can cause vit B12 deficiency
drug interactions:
omeprazole inhibits CYP2C19: diazepam, warfarin, phenytoin levels increase, clopidogrel activity may be reduced
all PPIs: decreased absorption of digozin and ketoconazole (increased gastric pH)

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15
Q

H2 antagonist may be beneficial at what time of day?

A

they show effect at night

PPIs work around the clock

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16
Q

acid rebound

A

inc gastric acid secretion upon withdrawal of suppressing medication (most common w H2 antagonists)
reduced gastric acid removes somatostatin inhibition of gastric secretion - hypergastrinemia

17
Q

sucralfate

A 
mucosal protective
aluminum hydroxide complex of sucrose
polymerizes and forms protective barrier at ulcer site
acidic pH activates complex
poorly absorbed
18
Q

misoprostol

A 
mucosal protective agent
semi-synthetic PG E1 derivative
reduced acid secretion (parietal cell)
cytoprotectant effects - enhanced mucus and bicarbonate secretion
used in combination with chronic NSAIDs 
adverse effects: diarrhea, abortifacient
19
Q

infection causing ulcers

A

H. pylori in the gastric mucosa
therapy: bismuth salt (pepto), antibiotic (metronidazole, tetracycline, amoxicillin, clarithromycin), H2 or PPI, ranitide bismuth citrate

20
Q

pepto bismol

A

bismuth subsalicylate - converted to bismuth salts and salicylic acid in GI tract
antibacterial, antiviral and antisecretory activity
uses: treatment of mild diarhhea and part of therapy for H. pylori eradication

21
Q

drugs affecting GI motility

A

increase motility: laxative, prokinetic

decrease motility: antidiarhheals, antiemetics

22
Q

bulk and saline laxatives

A

psyllium, methylcellulose, bran, milk of magnesia, non-absorbable sugars
non-absorbable and form hydrophilic mass in the presence of water
inc water in the intestinal lumen by osmotic force, leading to distention and an increase in peristalsis
isosmotic electrolyte solutions with polyethylene glycol produce similar effects

23
Q

stool softeners

A

docusate sodium (colace), mineral oil, glycerin
surfactantants and lubricants
incorporate into stool to make passage easier and decrease water absorption
lubricate lower bowel to reduce fetal impaction
can decrease absorption of fat soluble vitamins

24
Q

stimulant laxatives

A

poorly understood mechanism
castor oil-hydrolyzed in the upper small intestine to ricinoleic acid
bisacodyl (dulcolax), cascara, senna, and aloes
stimulate peristalsis

25
Q

prokinetic drugs

A

can act on many parts of the cholinergic motor neuron / smooth muscle system that affects bowel movements increase GI motility

26
Q

metoclopramide

A

prokinetic drug
D2 dopamine receptor antagonist
-blockade of D2 receptors in the myenteric plexus leads to increase ACh release
-this blockade produces anti-emetic effects
-clinical uses: promotes gastric emptying to facilitate small bowel intubation, post-op and diabetic gastroparesis, GERD
side effects: sedation, EPS, hyperprolactinemia (hynecomastia, galactorrhea, breast tenderness)

27
Q

Chloride Channel activators

A

increase motility by increasing chloride-rich fluid secretion into intestine
for treatment of IBS + constipation
not absorbed systemically (low SE)
lubiprostone (amatiza) - stimulation of type 2 chloride channel (ClC-2) activator in small intestine
linaclotide (linzess) - a peptide activator of guanylate cyclase 2

28
Q

anti-diarrheals

A

slow peristalsis to increase water and electrolyte absorption
bismuth (pepto bismol)
bile-salt binding resins
-cholestryamine, colestipol, colesevam
-ion exhchange resins
-diseases of terminal ileum (Crohn’s)
-decrease diarrhea caused by osmotic imbalance due to excessive bile salts
decrease absorption of many drugs and fat-soluble vitamins

29
Q

opiates

A

inhibit presynaptic cholinergic nerves

  • diphenoxylate (with atropine to discourage OD; lomotil)
  • loperamide (imodium)
  • poorly traverse the BBB
  • act locally to delay gastric emptying
  • contraindicated in patients with severe ulcerative colitis and bacterially-induced diarrhea
30
Q

IBS

A

abdominal pain and distention + altered bowel habits
alosetron (lotronex) - 5HT3 receptor antagonist
-for women with IBS + diarrhea
-blocks visceral afferent pain sensation and decreases colon motility
-GI SE: constipation, ischemic colitis (sometimes fatal)
-withdrawn and reintroduced via a restricted prescribing program in 2002

31
Q

anticholinergics

A

dicyclomine and hyoscamine
inhibit muscarinic cholinergic receptors
antispasmodic
toxicity due to anticholinergic effects

32
Q

anti-emetics

A

serotonin receptor antagonists
ondansetron, granisetron, dolastron, palonostron
block activity in CTZ and vagal afferents from stomach and small intestine which activate CNS emetic centers
clinical use: NV associated with chemotherapy
SE: constipation

33
Q

treating NV in chemo

A

combine antiemetics with different properties

5HT3 + corticosteroids (enhance activity) or aprepitant (NK1 antagonist - brain receptors in chemoreceptor trigger zone)

34
Q

cannabinoids

A 
dronabinol (marinol), nabilone (Cesamet)
synthetic THC
treat NV associated with chemo therapy
limited to patients who are refractory to other agents
mechanism unclear
may experience psychoactive effects
35
Q

motion sickness treatment

A

antihistamines/anticholinergics
diphenhydramine - H1 antihistamine with ACh properties
meclizine - H1 antihistamine with minimal ACh properties
scopolamine - muscarinic receptor antagonist with significant ACh effects that are tolerated as a transdermal patch

36
Q

antipsychotics as antiemetics

A 
D2 dopamine receptor antagonists
antiemetic and sedative properties
prochloperazine (compazine), promethazine, thiethylperazine - also inhibit muscarinic receptors, antihistamine effects
droperidol - IV
metoclopramide, trimethobenzamide

GI and liver (10 decks)

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