Drugs Affecting the GI System Flashcards
(116 cards)
1
Q
what are antacids?
A
weak bases that react with hydrochloric acid (HCl) to form a salt and water
2
Q
precautions with magnesium based antacids
A
caution in use with renal failure
a malfunctioning kidney is unable to excrete magnesium
3
Q
precaution with aluminum based antacids
A
prolonged use with renal failure may cause or worsen dialysis osteomalacia
- aluminum does not cross dialysis membrane
- elevated levels of aluminum in the tissue can cause dialysis encephalopathy
4
Q
precaution with ALL antacids
A
they have a high sodium content!
- should be used cautiously in those with HTN, CHF, marked renal failure, or anyone that should follow a low-sodium diet
5
Q
adverse drug reactions with antacids
A
aluminum and calcium based - may cause constipation
magnesium based - may cause diarrhea
6
Q
acid-neutralizing capacity (ANC)
A
expressed in mEq of HCl required to keep an antacid suspension at pH 3.5 for 10 min
- higher ANC values = more likely to be effective
- sodium bicarbonate and calcium bicarbonate have the highest ANC
- suspensions have greater ANCs than powders or tablets
7
Q
main factor in most duodenal ulcers
A
infection with H. pylori
8
Q
best treatment option for uncomplicated PUD
A
combining antacids with both aluminum hydroxide and magnesium hydroxide
9
Q
antacids and GERD
A
effective for daytime s/s
10
Q
antacids for acute management of GERD s/s
A
may be given every 30-60 min until s/s are relieved
11
Q
antacids for maintenance of GERD s/s
A
doses are given 1-3 hours after meals and at bedtime
12
Q
main factors used to choose an antacid
A
ANC
sodium content
cost
13
Q
patient education for antacids
A
- take 1-3 hours after meals and at bedtime
- taking calcium-based antacids with an acidic fruit juice may improve absorption
14
Q
methods to prevent constipation
A
- increased bulk in diet
- greater bulk in diet
- increase mobility
- stool softeners
14
Q
methods to prevent diarrhea
A
- increase fiber in diet
15
Q
lifestyle management for GERD
A
pts should avoid the following:
- smoking
- lying flat while sleeping
- eating foods that irritate the gastric mucosa (spicy foods)
- eating/drinking substances that stimulate acid production (alcohol)
- eating foods that decrease lower esophageal sphincter tone (fatty foods, chocolate, caffeine)
16
Q
acute diarrhea
A
lasting less than 2 weeks
17
Q
chronic diarrhea
A
lasting more than 4 weeks
18
Q
chronic diarrhea can result in
A
Weight loss
Dehydration
Perianal skin breakdown
Nutritional deficits
19
Q
diarrhea in children
A
can cause dehydration very quickly
20
Q
3 main classes of drugs used to treat diarrhea
A
- absorbent preparations
- opiates
- anticholinergics
21
Q
absorbent preparations for diarrhea
A
bismuth subsalicylate (Pepto-Bismol, Kaopectate Liquid)
22
Q
opiates for diarrhea
A
diphenoxylate with atropine (Lomotil)
difenoxin with atropine (Motofen)
loperamide (Imodium)
23
Q
anticholinergics
A
useful only for IBD
24
bismuth subsalicylate
o has antisecretory and antimicrobial effects
o may have some anti-inflammatory effects
o used as a part of a multi-drug regimen for eradication of H. pylori
25
precautions with pepto-bismol
contains aspirin -> should not be used in children
may turn tongue black, and stool green or black (not a GI bleed)
26
diphenoxylate with atropine for diarrhea
a constipating meperidine congener that lacks analgesic activity
o high doses (4-60mg) can cause opioid activity with chronic use
euphoria
physical dependence
o atropine - provides the anticholinergic effects that decrease secretion in the bowel and slow peristalsis
27
loperamide (Imodium)
binds to opiate receptors of the intestinal wall
leads to slowed gastric motility
reduces fecal volume
increases viscosity and bulk
diminishes the loss of fluid and electrolytes
28
crofelemer (Mytesi)
A botanical blocking chloride secretion from the epithelial cells in the intestinal lumen
Decreases water loss in diarrhea
Normalizes the flow of chloride and water in the intestinal tract
29
eluxadoline (Viberzi)
o A mu and kappa opioid receptor agonist, and a delta opioid receptor antagonist
o Has an affinity for the opioid receptors in the gut
30
alosetron (Lotronex)
o A potent and selective 5-HT3 receptor antagonist
o Acts on the 5-HT3 receptors in the GI tract
o Decreases bowel motility and secretion
o Decreasing abdominal pain
31
precautions with all antidiarrheals
Drugs the reduce intestinal motility or delay intestinal transit time have induced toxic megacolon, especially in patients w/ IBS
32
the atropine component of diphenoxylate and difenoxin
o Contraindicates their use in narrow-angle glaucoma
o Requires cautious use in prostatic hyperplasia
o Children have increased sensitivity to atropine
33
main adverse reaction with antidiarrheals
rebound constipation
34
treatment for simple, acute diarrhea
bismuth subsalicylate taken after each loose stool may be effective
35
if the absorbents do not resolve diarrhea...
diphenoxylate or difenoxin (both with atropine) or loperamide may be added
o Diphenoxylate with atropine - three to four times daily rather than after each loose stool
o Difenoxin with atropine - both after each stool or every 3 to 4 hours as needed to avoid exceeding the maximum 24-hour dose
36
treatment of chronic diarrhea with IBS
loperamide may be used as adjunct therapy
- 4mg initially, followed by 2-4 mg QID
37
diarrhea in HIV/AIDs pts taking antiretroviral drugs
Crofelemer (Mytesi) 125 mg BID
o Taking without regard to food
o Mean duration of therapy : 141 days
38
indications for antidiarrheals
o For acute diarrhea: any of the diarrheas are appropriate
o For more severe diarrhea: absorbent agents
o Traveler’s diarrhea: bismuth subsalicylate and loperamide
o Diarrhea w/ IBS: loperamide
39
adverse reactions with diphenoxylate and difenoxin (both with atropine)
dry mouth and mucous membranes
skin flushing
tachycardia
urinary retention
dizziness
drowsiness
loperamide can cause these CNS effects, but to a lesser extent
40
lifestyle management for diarrhea
- Add fiber to diet
- Using oral rehydration solutions (ORS)
- Bland diet
- Stopping consumption of milk and other lactose containing foods for a few days
- Maintain nutrition
o Do not stop food intake!
o Rest GI tract briefly (approx. 24 hrs) may be appropriate, but pts should never reduce fluid intake
41
two agents used to treat or prevent formation of ulcers
cytoprotective agents
o Sucralfate (Carafate)
o Misoprostol (Cytotec)
42
pharmacodynamics sucralfate
Believed to act by polymerization and selective binding to necrotic ulcer tissue
Covers the ulcer site
Acts as a barrier to acid, pepsin, and bile salts
o No acid-neutralizing activity
o Stimulate endogenous prostaglandin synthesis
Prostaglandins: central to the formation and maintenance of the protective mucosa of the GI tract
43
principal MOA misoprostol
- inhibition of gastric secretion through inhibition of histamine-stimulated production of cyclic adenosine monophosphate (cAMP)
- Inhibits basal and nocturnal gastric secretion and acid secretion in response to a variety of stimuli
- has mucosal protective qualities
- produces uterine contractions -> do not use in pregnancy
44
treatment of duodenal ulcers associated with NSAID use
first option - d/c NSAIDs
if NSAIDs cannot be d/c -> misoprostol 200mcg QID w/ food, taken for the duration of NSAID therapy
45
treatment of duodenal ulcers from other causes: sucralfate
o Can be used short term (up to 8 weeks) for treatment of active duodenal ulcer
- Off label uses in treating gastric and esophageal ulcers with the same dosing schedule
o Can be used for stress ulcer prophylaxis
46
treatment of duodenal ulcers from other causes: misoprostol
o Less effective than H2Ras or PPIs for tx of duodenal ulcers from other causes
o Off-label use for tx of duodenal ulcers not responsive to H2Ras
Doses greater than 400 mcg/day
47
drug selection for duodenal ulcers
Sucralfate is preferred over misoprostol for tx of active duodenal ulcers not caused by NSAIDs
o cytoprotective drug of choice for women of childbearing age
48
pt education on cytoprotective drugs
- sucralfate: taken on empty stomach
- misoprostol: taken with food
49
antiemetics
- antihistamines
- phenothiazines
- sedative hypnotics
- cannabinoids
- 5-HT3 receptor antagonists (zofran)
- anticholinergics
- substanceP/NK1 receptor antagonist
- miscellaneous antiemetic: trimethobenzamide
50
pharmacodynamics of antihistamines as antiemetics
Have strong cholinergic effects, as well as histamine1-blocking effects
- Blockade of histamine1 receptors results in decreased exocrine gland secretion (EX: salivary and lacrimal)
1st generation antihistamines with strong anticholinergic properties bind to central cholinergic receptors which produce antiemetic effects
- Decreases nausea and vomiting
Especially helpful with nausea associated w/ motion sickness d/t their depression of conduction in the vestibulocerebellar pathway
51
antihistamines used as antiemetics
dimenhydrinate (Dramamine)
diphenhydramine (Benadryl)
hydroxyzine (Vistaril)
meclizine (Antivert)
52
phenothiazines used as antiemetics
prochlorperazine (Compazine)
perphenazine
promethazine (Phenergan)
53
pharmacodynamics of phenothiazines as antiemetics
- Block dopamine receptors in the chemoreceptor trigger zone (CTZ)
- Also bind to and block cholinergic, alpha1-adrenergic, and histamine1 receptors
- Use as antiemetics is limited by their sedating and extrapyramidal side effects
54
5-HT3 antagonists as antiemetics
palonosetron (Aloxi)
dolasetron mesylate (Anzemet)
granisetron (Kytril, Sancuso)
ondansetron (Zofran)
55
pharmacodynamics of 5-HT3 antagonists as antiemetics
Block serotonin both peripherally on vagal terminals and centrally in the CTZ
56
antihistamine containdications
severe liver disease
cautious use in patients with:
Narrow-angle glaucoma
Seizure disorders
Pyloric obstruction
Hyperthyroidism
CV disease
Prostatic hypertrophy
57
phenothiazines contraindications
- Narrow-angle glaucoma
- Bone marrow depression
- Severe CV or hepatic disease
- Parkinson's disease - may produce extrapyramidal reactions
* these drugs suppress the cough reflex -> caution with respiratory impairments
58
zofran ODT disintegrating tablets caution
contain aspartame -> should not be used in patient phenylketonuria
59
motion sickness treatment
antihistamines are used because they act on the vestibular system and the CTZ to help control the nausea and vomiting associated with vestibular dysfunction
60
histamine2 receptor antagonists
Inhibit acid secretion by gastric parietal cells through a reversible blockade of histamine at histamine2 receptors
61
H2RA uses
o To reduce gastric acid in patients who are temporarily not taking anything by mouth
o For prophylaxis and management of duodenal and gastric ulcers and GERD
o Treat heartburn, indigestion, and “sour stomach”
62
three H2RAs available in the US
o Cimetidine (Tagamet)
o Famotidine (Pepcid)
o Nizatidine (Axid)
63
H2RA effects
suppress basal and meal-stimulated acid secretion
- have a modest effect on meal stimulated acid, but a good effect on basal acid secretion
64
H2RAs for GERD
most effective is used as an on-demand therapy for relief for GERD s/s
- once-daily dosing of H2RAs are not effective in treating GERD
65
H2RAs for PUD
Eradication of H. pylori is needed to heal ulcers
- Continued acid suppression may be accomplished with H2Ras after the peptic ulcer has healed
66
prokinetics
also known as "gastrointestinal stimulants"
- Stimulate the motility of the GI tract without stimulating gastric, biliary, or pancreatic secretions
67
prokinetics uses
Used in the management of a wide variety of disorders in which reduced GI motility is a problem:
o Gastroparesis associated with DM
o GERD
o Emesis associated with cancer chemotherapy
o Chronic idiopathic constipation (CIC)
68
prokinetic medications
o Metoclopramide (Reglan)
o Prucalopride (Motegrity)
69
pharmacodynamics of prokinetics
o Increases the tone and amplitude of gastric contractions
o Relaxes the pyloric sphincter and duodenal bulb
o Increases peristalsis of the duodenum and jejunum
resulting in accelerated gastric emptying and increased speed of gastric transit
70
prokinetics boxed warning
Boxed warning for risk of developing tardive dyskinesia
o Risk increases with the length of treatment
o Treatment should not exceed 12 weeks, except in rare cases
71
clinical uses for metoclopramide
- GERD
- n/v
- diabetic gastroparesis
72
proton pump inhibitors
Antisecretory drugs used to treat gastric conditions characterized by hyperacidity
73
PPI uses
o Erosive gastritis
o GERD
o Zollinger-Ellison syndrome
o As part of a multidrug regimen for short-term treatment of active PUD -> Especially duodenal ulcers caused by H. pylori
74
PPIs are administered as prodrugs
they are going into a very acidic area
- often delayed release as acid-resistant enteric coated tablets/capsules -> can't be crushed or chewed
- do a better job at meal stimulated acid secretion than H2RAs
75
PPI pharmacodynamics
Do not exhibit anticholinergic or histamine2-blockade properties
DO suppress gastric acid secretion
- Reduce H+ secretion by inhibition of the H+/K+-ATPase enzyme system at the secretory surface of the parietal cell itself to block the final step in H+ secretion
- Inhibits basal and stimulated acid secretion regardless of the stimulus
- Reduce gastric acid by more than 90%
- Frequently produce achlorhydria
The decrease in acid secretion lasts for up to 72 hours
- Gastric acid secretion begins 3-5 days after the drug is discontinued
76
PPI long term use - nutrient deficiencies
can lead to significant nutrient deficiencies:
o Iron-deficiency anemia
o Vitamin B12 deficiency
o Calcium deficiency
o Pts with long term PPI use may be at increased risk for osteoporosis and increase hip fractures
77
PPI long term use - increased risk of infections
stomach acid provides a natural defense against microbial pathogens
patients on long term PPI therapy have an increased risk of infections from:
- c. diff
- salmonella
- campylobacter
78
medications used to tx active duodenal ulcer and active benign gastric ulcer
o Lansoprazole
o Omeprazole
o Esomeprazole
o Rabeprazole
o once daily dosing is taken before a meal, preferably in the morning
Treatment is for 12 weeks
79
all PPIs are approved for tx of GERD
Once daily dosing
Taken 30-60 min before breakfast x 8 weeks
Additional 4 weeks may be needed if pt is still symptomatic
* Also refer to GI dr
80
treatment for constipation
The pathophysiology of constipation varies with its cause -> the action of the drug chosen to treat the constipation must also vary to match the cause
81
six conventional classes of laxatives
o Stimulants
o Osmotics
o Bulk-producing laxatives
o Lubricants
o Surfactants
o Hyperosmolar laxatives
82
pharmacodynamics stimulant laxatives
Have a direct action on intestinal mucosa by stimulating the myenteric plexus
o Facilitate the release of prostaglandins
o Increase cAMP concentration -> Higher levels of cAMP increase the secretion of electrolytes and stimulates peristalsis
83
stimulant laxative drugs
o Cascara
o Senna
o Bisacodyl
o Castor oil
84
stimulant laxatives are used to treat
o Constipation associated w/ reduced mobility
o Constipating drugs
o Reduced motility
o Neurogenic bowel secondary to spinal cord injury
o IBS
85
pharmacodynamics - osmotic laxatives
- Draw water into the intestinal lumen to increase intraluminal pressure
- Are hypertonic salt-based solutions that cause the diffusion of fluid from the plasma into the intestine to dilute the solution to an isotonic state
- Magnesium salts -> Cause an increase in the release of cholecystokinin by the duodenum
- Sulfate salts -> Considered the most powerful
86
osmotic laxative medications
- Magnesium hydroxide
- Magnesium citrate
- Sodium phosphate
- Polyethylene glycol electrolyte solution
- polyethylene glycol (PEG) 3350
87
bulk-producing laxative pharmacodynamics
Safest and physiologically the easiest
- Their action is similar to that achieved by increasing fiber in the diet
Consist of natural and semisynthetic polysaccharides and cellulose
- When combined with water in the intestines -> produce mechanical distention -> results in increased peristalsis
88
bulk-producing laxative medications
o Psyllium (Metamucil)
o Methylcellulose
o Polycarbophil
89
bulk-producing laxative uses
o Long-term management of simple, chronic constipation -> Especially if it is related to low fiber intake
o Situations when straining at stool is to be avoided
o Chronic, watery diarrhea must be managed
90
hydration with bulk-producing laxatives
if pts do not hydrate adequately, more constipation can result
91
lubricant laxatives
- Mineral oil is the main ingredient -> Retards colonic absorption of fecal water and softens the stool
- Used to soften stool associated with fecal impaction
- Main concern -> it may decrease absorption of fat-soluble vitamins
92
surfactant laxatives pharmacodynamics
Reduce the surface tension of the oil-water interface on the stool
- Facilitate a mixture of fat and water into the stool -> producing an emollient action
93
what are surfactant laxatives known as?
stool softeners
94
surfactant laxative medications
o Docusate sodium
o Docusate calcium
o Docusate potassium
95
surfactant laxatives are most beneficial when
o Feces are hard or dry
o Passage of firm stool is painful because of an anorectal condition
o Straining at stool is to be avoided
96
glycerin pharmacodynamics
Glycerin produces local irritation, and as a hyperosmotic compound, draws water from the extravascular spaces into the lumen of the intestine -> result in more liquid stool
97
hyperosmolar laxative medications
- lactulose
- glycerin
98
lactulose pharmacodynamics
A hyperosmotic disaccharide
In the colon, bacteria transform the drug into lactic, acetic, and formic acids
* These acids exert an osmotic effect by drawing water from the extravascular spaces into the intestinal lumen
99
lactulose uses
Used to treat chronic constipation in older adults
Used to treat hepatic encephalopathy
- Lowers the pH of the colon -> inhibits the diffusion of ammonia across the colonic membranes
100
glycerin uses
Used to treat fecal impaction and patients with neurogenic bowel (the bowel is filled with feces that cannot be evacuated)
101
all laxatives are contraindicated in the presence of:
o n/v
o undiagnosed abdominal pain
o bowel obstruction is suspected or diagnosed
102
choice of drug to treat constipation depends on
o severity
o underlying cause
o speed at which the result is needed
103
rapid response and short term use laxatives
stimulants are the drug of choice
osmotic laxatives work as well
- magnesium hydroxide: 6-8 hrs
- PEG 3350: 1-3 days
104
slower response and long term laxative use
bulk forming laxatives are the drug of choice
105
special indications for laxatives
o Polyethylene glycol electrolyte solution is the best drug for cleansing the bowel in prep for radiological or surgical procedures
o Lactulose is effective in reducing ammonia levels in the blood and brain in hepatic encephalopathy
106
laxatives in pregnancy
- Bulk-forming laxatives and surfactants are safe and effective for regular use
- Magnesium hydroxide can be used intermittently
107
lifestyle management for constipation
prevention is key
- adequate fiber, fluids, and exercise
108
other drugs for chronic constipation
others treatments may be needed if constipation is not relieved by convention laxatives
Newer drugs including:
- Chloride channel activators
-- 5HT4 receptor agonists
-- Guanylate-cyclase-C (GC-C) agonists
- Opioid receptor antagonists
109
pharmacodynamics lubiprostone (Amitiza)
Activates CIC-2 chloride channels in the GI epithelial lining
Produces chloride-rich secretions that:
- Soften the stool
- Increase GI motility
110
Lubiprostone (Amitiza) uses
Chronic idiopathic constipation (CIC)
Irritable bowel syndrome (IBS-C)
Opioid induced constipation
111
5HT4 receptor agonist for constipation
Prucalopride (Motegrity)
- Stimulates colonic motility
- Used to treat CIC
112
Guanylate Cyclase-C Receptor Agonists medications
o Linaclotide (Linzess)
o plecanatide (Trulance)
113
Guanylate Cyclase-C Receptor Agonists pharmacodynamics
bind to guanylate cyclase-C (GC-C) on the intestinal epithelium r
results in:
- increased intestinal fluid
- accelerated transit
114
opioid receptor antagonists medications
o Methylnaltrexone
o Naloxegol
o Naldemedine
115
opioid receptor antagonist for constipation
- Work as antagonists to the mu-receptor in the GI tract
- Treats constipation experienced with opioids
- Do not affect the analgesic effect of opioids
