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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
Q

Potential Side effects of bulk laxatives?

A

Allergies
Flatulence
Obstruction

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26
Q 
What is the latency period like for bisacodyl?
What class of drug is it?
A

Long! 6 hours…it is given as a prodrug!

Contact cathartic

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27
Q

What is a super serious side effect of castor oil?

A

Induces uterine contractions!

DON’T GIVE TO PREGNANT LADY

28
Q

Some rare side effects of contact cathartics? (bisacodyl, anthraquinones, castor oil)

A

Dependency

Destruction of myenteric plexus

29
Q

What is melanosis coli?

A

Pigmentation of mucosa due to contact cathartics…harmless!

30
Q

What does the suffix “-setron” mean?

A

5HT3 antagonist

31
Q

Alosetron has some pretty serious side effects, what are they?

A

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
Q

MOA of Tegaserod?

A

5HT4 agonist….increases release of serotonin from afferent neurons…increases peristalsis!

33
Q

When do you use Tegaserod?

Why?

A

No other options for constipation-predominant IBS

34
Q

Why was Cisapride pulled off the market?

MOA?

A

Cardiovascular toxicity…Long QT syndrome

5HT4 agonist and 5HT3 antagonist

35
Q

What does enkaphalin do to peristalsis?

A

Decreases it

36
Q

Side effects of Loperamide, Diphenoxylate?

A

Abdominal cramps
Toxic megacolon if person has ulcerative colitis
*Diphenoxylate: at high doses can cause euphoria leading to physical dependence

37
Q

Do Alvimpoan and methylnaloxone cross the BBB?

A

NO

38
Q

Which patients receive Alvimopan or Methylnaloxone?

A

Short term, hospitalized patients on opioids or long term palliative care patients

39
Q

Side effect of mu receptor antagonists?

A

Increased incidence of MI

40
Q

Besides being a prokinetic, what else does metoclopramide do?

A

Anti-emetic!

41
Q

Side effects of the D2 receptor antagonists?

A

Somnolence, nervousness, agitation, anxiety
Dystonia, Parkinsonism, tardive dyskinesia (irreversible)
Increase prolactin release can lead to impotence, menstrual disorders, galactorrhea

42
Q

What 2 TCAs are used for tx of IBS?

How do they work?

A

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
Q

MOA of Lubiprostone?

When is it used?

A

Activates CIC2….increasing Chloride secretion

*Poorly absorbed, almost no systemic effects

Used for chronic constipation and constipation-predominant IBS

44
Q

What is a significant side effect of Lubiprostone?

A

Increased fetal loss…Pregnancy Class C!

45
Q

What is the MOA of Linaclotide?

A

Activates guanylyl cyclase C ….increasing cGMP….activating CFTR….increasing chloride secretion….increasing water in the lumen!

46
Q

Some significant side effects of Linaclotide?

A 
Pregnancy class C (maternal death)
Can't use in pediatric patients...increased mortality
47
Q

MOA of Crofelemer?

A

Voltage Independent Inhibition of CFTR (and another chloride channel)….decreasing chloride secretion….decresing water secretion….FIRMER STOOL

48
Q

When is Crofelemer generally given?

A

To tx diarrhea due to anti-HIV drug tx

49
Q

What has a longer half-life, Octreotide or somatostatin?

A

Octreotide!

50
Q

MOA of octreotide?

A

Somatostatin analogue….
Decreased fluid secretion

At LOW doses….it INCREASES motility
At HIGH doses…it DECREASES motility

51
Q

What are the off-label uses of Octreotide?

A

Severe diarrhea due to dumping syndrome, short bowel-syndrome, vagotomy, AIDS

52
Q

Side effects of Octreotide? (theres a lot)

A

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
Q

MOA of Bismuth Subsalicylate?

A

Salicylate: decreases PG and chloride secretion in LARGE INTESTINE
Antimicrobial, binds enterotoxins

54
Q

Therapeutic use of bismuth subsalicylate?

A

PREVENTION of diarrhea

Tx of travellers diarrhea

55
Q

MOA of osmotic cathartics?

A

not absorbed so they increase water in the lumen (osmosis)

56
Q

What does lactulose do?

A

Decreases plasma ammonia concentration! Tx for hepatic encephalopathy!

57
Q

What drugs are the osmotic cathartics?

A

Lactulose
Magnesium hydroxide
sodium phosphate
polyethylene glycol

58
Q

Side effect of Lactulose?

A

SEVERE cramps, flatulence, discomfort because it is metabolized by gut bacteria

59
Q

Which drugs are the bile acid binding resins?

A

Cholestyramine

Colestipol

60
Q

MOA of bile acid binding resins?

A

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
Q

What acts as a surfactant to lubricate stool?

A

Docusate

62
Q

What lubricates stool directly?

A

Mineral oil

63
Q

What condition are prokinetic agents especially useful for?

A

Diabetic gastroparesis

64
Q

What are the 3 types of prokinetic agents?

A

D2 receptor antagonists (metoclopramide)
Macrolides (erythromycin)
5HT4 agonists (Cisapride)

65
Q

What type of diarrhea can you not use antidiarrheals for?

A

BLOODY

GI Week 4 (8 decks)

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