A.37. Drugs used in constipation (laxatives) and diarrhea. drugs promoting digestion. Pharmacology of liver and biliary tract.

Question 1

how are laxatives classified?

Answer 1

based on their mechanism of action:

1. irritants and stimulants
2. bulk-forming laxatives
3. osmotic laxatives
4. stool softeners
5. lubricant laxatives

Question 2

what are laxatives used for?

Answer 2

constipation

*may cause electrolyte imbalance when used chronically

Question 3

what are sennoside and Bisacodyl?

Answer 3

irritants and stimulants

Question 4

what classification does plant fiber belong to?

Answer 4

bulk-forming laxatives

Question 5

list 3 osmotic laxatives

Answer 5

magnesium-sulphate
lactulose
glycerol

Question 6

what is paraffin oil?

Answer 6

lubricant laxative

Question 7

what does paraffin oil do?

Answer 7

facilitate the passage of hard stools

Question 8

how paraffin oil should be taken?

Answer 8

orally in an upright position to avoid aspiration and potential lipoid pneumonia

Question 9

what does Sennoside do?

Answer 9

irritant of the colonic wall to induce fluid secretion and colonic motility

Question 10

how is Sennoside taken?

Answer 10

orally (causes evacuation of the bowels within 8-10 hours)

rectally (within minutes)

Question 11

when do we give Sennoside?

Answer 11

1. treatment for opioid-induced constipation
2. evacuation of the bowel prior to surgery
3. before invasive rectal/colonic examinations

Question 12

what is the function of Bisacodyl

Answer 12

potent stimulant of the colon, acts on the nerve fibers in the colonic mucosa

Question 13

when do we use Bisacodyl

Answer 13

1. chronic constipation
2. neurologic bowel dysfunction
3. pre-operative preparartion

Question 14

what are the adverse effects of Bisacodyl

Answer 14

abdominal cramps 
atonic colon (prolonged use)
might damage the enteric protective coating

Question 15

what are the SE of taking plant fibers

Answer 15

can cause obstruction and meteorism

Question 16

what is the effect of plant fibers?

Answer 16

form gels in the large intestine –> causing water retention –>increased peristaltic activity

Question 17

what is the effect of magnesium- sulfate as a laxative?

Answer 17

non-absorbable salt
hold water in the intestinal lumen by means of osmosis distended the bowel–> ↑ intestinal activity–> produces defecation in a few hours

Question 18

what is Lactulose?

Answer 18

semisynthetic disaccharide sugar
cannot be hydrolyzed by intestinal enzymes
degraded by colonic bacteria into lactic, formic, and acetic acids.
↑ osmotic pressure –> fluid accumulation

Question 19

what other indication does Lactulose have other than as a laxative?

Answer 19

hepatic encephalopathy (reduces ammonia levels)

Question 20

list the antidiarrheal agents

Answer 20

Loperamide
Diphenoxylate
activated charcoal

Question 21

what are the indications for giving antidiarrheal agents?

Answer 21

non-specific, non-infectious diarrhea

loperamide–> also IBS with diarrhea

Question 22

how are antidiarrheal agents given?

Answer 22

orally

Question 23

what type of metabolism do loperamide and diphenoxylate have?

Answer 23

hepatic P450

Question 24

does Loperamide cross the blood-brain barrier?

Answer 24

no

Question 25

does Diphenoxylate cross the blood-brain barrier?

Answer 25

yes, at higher doses

Question 26

what is the SE of loperamide?

Answer 26

abdominal cramps

Question 27

what are the SE of Diphenoxylate

Answer 27

abdominal cramps | at higher doses--> CNS effects and toxicity

Question 28

how is Diphenoxylate given to reduce abuse liability?

Answer 28

with a muscarinic antagonist (atropine)

Question 29

what are Loperamide and Diphenoxylate?

Answer 29

synthetic opioid derivatives activate µ receptors in the enteric nervous system--> inhibit Ach release--> ↓ motility minimal analgesic effects

Question 30

what is the effect of activated charcoal as an antidiarrheal agent

Answer 30

attract and expel ingested toxins from the GI

Question 31

what does N-acetylcysteine do?

Answer 31

provide -SH groups

Question 32

how is N-acetylcysteine given?

Answer 32

oral, IV, inhaled

Question 33

side effects of N-acetylcysteine

Answer 33

nausea, vomiting | anaphylaxis like allergic reaction

Question 34

what is the T1/2 of N-acetylcysteine?

Answer 34

5-6 hours

Question 35

what is N-acetylcysteine used for?

Answer 35

``` acetaminophen toxicity --> best given within 8-10 h' of overdose. (20 gr) mucolytic agent (used in COPD and CF) ```

Question 36

what is the function of Ursodeoxycholic acid (Ursodiol)?

Answer 36

1. reduces cholesterol absorption 2. dissolve cholesterol gallstones 3. anti-inflammatory effects on the GI

Question 37

how is Ursodeoxycholic acid (Ursodiol), Silymarin and resins given?

Answer 37

orally

Question 38

contraindications for Ursodeoxycholic acid (Ursodiol)?

Answer 38

acute hepatitis | Billary obstruction

Question 39

a side effect of Ursodeoxycholic acid (Ursodiol)

Answer 39

diarrhea

Question 40

indications for giving Ursodeoxycholic acid (Ursodiol)

Answer 40

cholelithiasis (patients unfit for cholecystectomy) prophylaxis (patients undergoing rapid weight loss or bariatric surgery) primary biliary cirrhosis (PBC)

Question 41

what is Silymarin?

Answer 41

liver protective agent | milk thistle extract derived from fruit and seeds of 'Silybum marianum'

Question 42

what are the indications for giving Silymarin

Answer 42

1. protects against liver injury caused by alcohol, acetaminophen and amanita mushrooms 2. antidote to Amanita phalloids mushroom poisoning

Question 43

what is Colesevelam

Answer 43

Resin | bile acid sequestrant

Question 44

what is the function of Colesevelam

Answer 44

A non-absorbable polymer that binds bile acids in the intestine and prevents their absorption- ↓ enterohepatic recirculation

Question 45

what drugs do resins interfere with their absorption?

Answer 45

warfarin, thiazides, digoxin, aspirin and statins | administer 4 h' apart

Question 46

when do we give resins (colesevelam)?

Answer 46

dyslipidemia (with statins) | ↓ pruritus in patients with cholestasis and bile acid accumulation

Question 47

side effects of resins

Answer 47

↑ VLDL and triglycerides GI disturbances malabsorption of lipid-soluble vitamins hyperglycemia