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GI Week 4 > Lower GI Drugs Fitz > Flashcards

Lower GI Drugs Fitz Flashcards

1
Q

How do bulk laxatives work?

A

Increase the mass of the stool

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2
Q

What 2 factors limit the use of bulk laxatives?

A
  1. The circuit responsible for generating the peristaltic reflex bust be functional
  2. The cause of constipation must be known
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3
Q

What works on both the small and large intestine, has a short latency, and extremely potent effects?

A

Castor Oil

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4
Q

What are the most effective anti-diarrheal drugs?

A

Loperamide and Diphenoxylate

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5
Q

What do the opiates do?

A

Decrease GI motility and decrease water excretion

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6
Q

What opiate is available OTC because it has little potential for addiction?

A

Loperamide

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7
Q

What 2 mu receptor antagonists can be used to offset the constipation caused by opiate analgesics?

A

Alvimopan

Methylnaltroxone

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8
Q

What drug targets CIC2 in the colon?

What kind of transporter?

A

Lubiprostone

Chloride transporter

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9
Q

What drugs target CFTR in the colon?

A

Linaclotide (activates GC)

Crofelemer (inhibits CFTR)

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10
Q

What do osmotic cathartics do to osmotic load?

A

Increase the osmotic load in the colon

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11
Q

What do bile acid binding resins do to osmotic load?

A

Decrease the osmotic load in the colon

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12
Q

If absorbed systemically, what can ALL osmotic laxatives do?

A

Cause intravascular volume depletion and electrolyte imbalances (hyperphosphatemia, hypernatremia……hypocalcemia, hypokalemia)

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13
Q

Even though stool softeners are considered the mildest laxatives, when should they not be used?

A

Cases of undiagnosed abdominal pain

Unknown intestinal pathology

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14
Q

What can mineral oil cause if aspirated?

A

Severe lipid pneumonitis

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15
Q

What may long term use of mineral oil result in?

A

Decreased absorption of fat soluble vitamins

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16
Q

Where do prokinetic agents increase motility?

A

ENTIRE GI TRACT (not just the colon)

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17
Q

What is a major side effect of Cisapride?

What kind of drug is Cisapride?

A

Severe cardiac side effects

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18
Q

What is the limited use for bile acid binding resins?

A

Diseases of the terminal ileum

Surgical resection resulting in decreased bile salt reabsorption

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19
Q

In which populations should osmotic laxatives be used with caution?

A

Frail
Elderly
Renal insufficient
Cardiac disease

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20
Q

What should patients do before trying prescription laxatives?

A

Modify diet
Increase fluid intake
Physical activity

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21
Q

MOA of Alosetron?

What is it used for?

A

5HT3 antagonist
Decreases afferent stimulation…decreasing peristalsis
Diarrhea-predominant IBS (use after everything else has failed)

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22
Q

MOA of Tegaserod?

What is it used for?

A

5HT4 antagonist

Constipation-predominant IBS

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23
Q

Why are SSRIs effective in tx of constipation-predominant IBS?

A

They decrease reuptake of serotonin into EC cells…therefore there is more serotonin in the synapse…an increase in afferent activity….and an increase in peristalsis!

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24
Q

How do bulk laxatives work?

A

They increase the stool mass, therefore distending the lumen so sensory receptors can begin to fire and increase peristalsis!

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25
Potential Side effects of bulk laxatives?
Allergies Flatulence Obstruction
26
``` What is the latency period like for bisacodyl? What class of drug is it? ```
Long! 6 hours...it is given as a prodrug! | Contact cathartic
27
What is a super serious side effect of castor oil?
Induces uterine contractions! | DON'T GIVE TO PREGNANT LADY
28
Some rare side effects of contact cathartics? (bisacodyl, anthraquinones, castor oil)
Dependency | Destruction of myenteric plexus
29
What is melanosis coli?
Pigmentation of mucosa due to contact cathartics...harmless!
30
What does the suffix "-setron" mean?
5HT3 antagonist
31
Alosetron has some pretty serious side effects, what are they?
Constipation in 30 % of patients...10 % have to stop its so bad. Some will need hospitalization. A small percent will get ischemic colitis that can be fatal *Increased risk with inhibitors of CYP1A2 inhibitors & substrates (some antidepressants!)
32
MOA of Tegaserod?
5HT4 agonist....increases release of serotonin from afferent neurons...increases peristalsis!
33
When do you use Tegaserod? | Why?
No other options for constipation-predominant IBS
34
Why was Cisapride pulled off the market? | MOA?
Cardiovascular toxicity...Long QT syndrome | 5HT4 agonist and 5HT3 antagonist
35
What does enkaphalin do to peristalsis?
Decreases it
36
Side effects of Loperamide, Diphenoxylate?
Abdominal cramps Toxic megacolon if person has ulcerative colitis *Diphenoxylate: at high doses can cause euphoria leading to physical dependence
37
Do Alvimpoan and methylnaloxone cross the BBB?
NO
38
Which patients receive Alvimopan or Methylnaloxone?
Short term, hospitalized patients on opioids or long term palliative care patients
39
Side effect of mu receptor antagonists?
Increased incidence of MI
40
Besides being a prokinetic, what else does metoclopramide do?
Anti-emetic!
41
Side effects of the D2 receptor antagonists?
Somnolence, nervousness, agitation, anxiety Dystonia, Parkinsonism, tardive dyskinesia (irreversible) Increase prolactin release can lead to impotence, menstrual disorders, galactorrhea
42
What 2 TCAs are used for tx of IBS? | How do they work?
Amitriptyline Desipramine They decrease reuptake of NE from postganglionic sympathetic neurons...increasing activation of alpha 2 on presynaptic terminals of ACh postganglionig parasympathetic nerves...decreasing ACh release...Decreaing motility
43
MOA of Lubiprostone? When is it used?
Activates CIC2....increasing Chloride secretion *Poorly absorbed, almost no systemic effects Used for chronic constipation and constipation-predominant IBS
44
What is a significant side effect of Lubiprostone?
Increased fetal loss...Pregnancy Class C!
45
What is the MOA of Linaclotide?
Activates guanylyl cyclase C ....increasing cGMP....activating CFTR....increasing chloride secretion....increasing water in the lumen!
46
Some significant side effects of Linaclotide?
``` Pregnancy class C (maternal death) Can't use in pediatric patients...increased mortality ```
47
MOA of Crofelemer?
Voltage Independent Inhibition of CFTR (and another chloride channel)....decreasing chloride secretion....decresing water secretion....FIRMER STOOL
48
When is Crofelemer generally given?
To tx diarrhea due to anti-HIV drug tx
49
What has a longer half-life, Octreotide or somatostatin?
Octreotide!
50
MOA of octreotide?
Somatostatin analogue.... Decreased fluid secretion At LOW doses....it INCREASES motility At HIGH doses...it DECREASES motility
51
What are the off-label uses of Octreotide?
Severe diarrhea due to dumping syndrome, short bowel-syndrome, vagotomy, AIDS
52
Side effects of Octreotide? (theres a lot)
Impaired pancreatic secretion...decreased fat absorption...fat soluble vitamin def. decreased GI motility (depending on dose)...nausea, abdominal pain, flatulence decreased gallbladder contractility....gallstones in 50 % of patients Insulin/glucagon imbalance...hypo or hyper glycemia Hypothyroidism & bradycardia
53
MOA of Bismuth Subsalicylate?
Salicylate: decreases PG and chloride secretion in LARGE INTESTINE Antimicrobial, binds enterotoxins
54
Therapeutic use of bismuth subsalicylate?
PREVENTION of diarrhea | Tx of travellers diarrhea
55
MOA of osmotic cathartics?
not absorbed so they increase water in the lumen (osmosis)
56
What does lactulose do?
Decreases plasma ammonia concentration! Tx for hepatic encephalopathy!
57
What drugs are the osmotic cathartics?
Lactulose Magnesium hydroxide sodium phosphate polyethylene glycol
58
Side effect of Lactulose?
SEVERE cramps, flatulence, discomfort because it is metabolized by gut bacteria
59
Which drugs are the bile acid binding resins?
Cholestyramine | Colestipol
60
MOA of bile acid binding resins?
Bind to unabsorbed bile acids...decreasing water secretion! *used when there is a decreased reabsorption of bile salts due to Crohn's, ileum resection etc.
61
What acts as a surfactant to lubricate stool?
Docusate
62
What lubricates stool directly?
Mineral oil
63
What condition are prokinetic agents especially useful for?
Diabetic gastroparesis
64
What are the 3 types of prokinetic agents?
D2 receptor antagonists (metoclopramide) Macrolides (erythromycin) 5HT4 agonists (Cisapride)
65
What type of diarrhea can you not use antidiarrheals for?
BLOODY

GI Week 4 (8 decks)

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