Small and Large Bowel pharmacology

Question 1

How do bulk forming agents work

Answer 1

absorb water, increase stool bulk

Question 2

Bulk forming agents are usually used to treat ______ but can be used in some mild forms of diarrhea

Answer 2

constipation

Question 3

Clays such as _____ bind water avidly and may also bind enterotoxins and are used to treat mild diarrhea

Answer 3

kaolin

Question 4

Describe the mechanism of action of bismuth subsalicylate

Answer 4

Thought to have antisecretory, anti-inflammatory, and antimicrobial effects
Used to prevent and treat traveler’s diarrhea
Common antibacterial used in treatment of H. pylori

Question 5

List two opioids used to treat diarrhea

Answer 5

loperamide

diphenoxylate + atropine

Question 6

What are side effects of loperamide?

Answer 6

dry mouth, dizziness, drowsiness, vomiting, stomach pain, discomfort, or distention, constipation, fatigue

Question 7

Why is atropine added to diphenoxylate?

Answer 7

to prevent abuse of the drug because it has modent CNS effects
the atropine also serves to decrease mucus and secretions from the bowel

Question 8

How does cholestyramine work to treat diarrhea?

Answer 8

Cholestyramine binds excess bile salts that cause secretory diarrhea
Useful when the terminal ileum has been resected or is diseased, which results in impaired bile clearance

Question 9

Why can cholestyramine not be taken within several hours of any other medication?

Answer 9

will absorb many medications

Question 10

Cholestyramine can cause significant bloating and even ________

Answer 10

stool impaction

Question 11

_____ is a somatostatin analog that is used to treat diarrhea

Answer 11

octreotid

Question 12

How does octreotide work?

Answer 12

somatostatin analog
decreasing pancreatic secretions and intestinal fluid secretion. Stopping the release gastrin, cholecystokinin, and serotonin
Also decreases portal flow and pressure- used in acute variceal bleed

Question 13

What are downsides to octreotide?

Answer 13

expensive, inconvenient, side effects of pain/ nausea/ diarrhea

Question 14

________ is a 5 HT3 antagonist used to treat IBS-D that is only effective in women

Answer 14

alosetron

Question 15

List conditions that can NOT be treated with alosetron

Answer 15

constipation, colitis, stricture, megacolon, ischemic colitis
was initially associated with colon ischemia

Question 16

What are two general mechanisms of drugs used to treat constipation?

Answer 16

• increased fluid by osmotic mechanisms or by decreased net absorption of fluids by impacting fluid and electrolyte transport
• increased forward motility- stimulation of contractions

Question 17

List classes of luminally active agents used for constipation

Answer 17

• hydrophilic colloids: bulk forming agents, methylcellulos, synthetic fibers
• osmotic agents- non absorbable salts or sugars
• stool wetting agents- surfactants and emollients

Question 18

Describe stool softeners used to treat constipation

Answer 18

Docusate sodium. Simple inexpensive treatment. A bit like ‘mucus in a pill.’
Used alone or as part of a more complex bowel regimen.

Question 19

List nonabsorbed sugars and salts that are used as osmotic agents to treat constipation

Answer 19

magnesium hydroxide
lactulose
sorbitol

all lead to bloating, cramping

Question 20

What is the mechanism of action of diphenylmethylanes, antraquinones (senna, cascara), and castor oil?

Answer 20

stimulants or irritants that affect colonic motility

Question 21

______ is used in low doses to treat constipation and in high doses as colonoscopy prep

Answer 21

polyethylene glycol

Question 22

______ is a drug that stimulates calcium channels in order to increase motility

Answer 22

lubiprostone

Question 23

What is the mechanism of action of methylnaltrexone?

Answer 23

opioid antagonist

used to treat opioid induced constipation and post-op ileus