Laxatives and cathartics

Question 1

What are examples of stool softeners?

Answer 1

Docusate

Mineral oil

Question 2

What is the MoA of docusate?

Answer 2

Surfactant –> allows mixing of aqueous and fatty substances

Question 3

What is the MoA of mineral oil?

Answer 3

Lubricates feces –> decreased water absorption from stool

Question 4

What are the side effects of mineral oil?

Answer 4

Severe lipid pneumonitis if aspirated

Fat-soluble vitamin deficiency

Question 5

What are examples of bulk laxatives?

Answer 5

Dietary fiber
Methycellulose
Psyllium

Question 6

What is the MoA of bulk laxatives?

Answer 6

Increase mass of stool –> distension –> enteric reflex –> increased GI motility

Question 7

What is required for bulk laxatives to be effective?

Answer 7

Functional enteric plexus

Question 8

Can bulk laxatives be used if the constipation is of unknown origin?

Answer 8

No

Question 9

What are the stimulant (contact) cathartics?

Answer 9

Anthraquinone derivatives
Bisacodyl
Castor oil

Question 10

What are examples of anthraquinone derivatives?

Answer 10

Cascara sagrada
Danthron
Senna

Question 11

Where do anthraquinone derivatives work?

Answer 11

Only the large intestine

Question 12

What are the side effects of anthraquinone derivatives?

Answer 12

Dependence

Brown pigmentation of colonic mucosa**

Question 13

Is bisacodyl commonly used?

Answer 13

No…cardiac toxicity

Question 14

If bisacodyl was used, where would it work?

Answer 14

Only the large intestine

Question 15

What is castor oil converted to to become activated?

Answer 15

Ricinoleic acid

Question 16

Where is castor oil effective?

Answer 16

Small AND large intestine

Question 17

What are some pharmacokinetics of castor oil?

Answer 17

Short latency

Very potent

Question 18

What are some side effects of castor oil?

Answer 18

Dependence

Dehydration with electrolyte imbalance

Question 19

What are examples of osmotic (saline) cathartics?

Answer 19

Lactulose
Magnesium hydroxide
Sodium phosphate
Polyethylene glycol solution

Question 20

Why shouldn’t magnesium hydroxide be used to treat constipation in renal insufficient patients?

Answer 20

Hypermagnesemia and death

Question 21

How can polyethylene glycol solution be used to treat constipation?

Answer 21

Hasten removal of toxins and reduce absorption

Whole body irrigation –> enhanced decontamination

Question 22

When is polyethylene glycol solution commonly used?

Answer 22

Before endoscopic procedures

Question 23

What is the MoA of osmotic cathartics?

Answer 23

Increase water and electrolyte concentrations in colon via osmosis

Question 24

What can lactulose be used for?

Answer 24

Reduces plasma ammonia concentrations

Treating portal-systemic encephalopathy

Question 25

What are some side effects of the saline cathartics?

Answer 25

Drug interactions | Intravascular volume depletion and electrolyte imbalances

Question 26

Who should be watched when treating with osmotic cathartics?

Answer 26

Old frail people with renal or cardiac disease

Question 27

What is the MoA of lubiprostone?

Answer 27

Activates Cl- channel --> increases liquid secretion (only effects channels on apical membranes of GI epithelial cells)

Question 28

What was lubiprostone developed to be?

Answer 28

A prokinetic drug...they're still working on it

Question 29

What is lubiprostone used to treat?

Answer 29

Chronic, idiopathic constipation | Constipation-predominant IBS

Question 30

What are some side effects of lubiprostone?

Answer 30

Diarrhea Delayed gastric emptying --> nausea/headache Increased fetal loss...DON'T give to pregos

Question 31

What are examples of opioid receptor agonists used to treat constipation?

Answer 31

Alvimopan | Methylnaltrexone

Question 32

When is alvimopan used?

Answer 32

Short term...like if there is a postoperative ileum following small or large bowel resection

Question 33

What are the side effects of alvimopan?

Answer 33

Cardiotoxicity...which is why it used short term

Question 34

When is methylnaltrexone used?

Answer 34

Long term...like in palliative care

Question 35

What is the MoA of opioid receptor agonists treating constipation?

Answer 35

Selective u receptor agonists Don't cross BBB