Lower GI Pharmacology

Question 1

CTZ (in the context of vomiting) stands for ____________.

Answer 1

chemoreceptor trigger zone

Question 2

The output vomiting center is in the ____________.

Answer 2

medulla

Question 3

What drugs are good for treating the nausea and vomiting induced by chemotherapy?

Answer 3

Ondansetron and the other 5HT3 blockers

Question 4

Other than diphenhydramine, what are two first-generation antihistamines?

Answer 4

Meclizine

Promethazine

Question 5

You order an antiemetic for a cancer patient receiving 5-fluorouracil. Her BP drops afterward, and you’re reconsidering your order. What drug did you give her?

Answer 5

Prochlorperazine (which has some alpha-1 blockade)

Question 6

Which laxative most closely approximates the physiologic mechanism of stool passage?

Answer 6

Psyllium (Metamucil) – a bulk-forming agent that induces peristalsis

Question 7

How do the osmotic laxatives work? What are some osmotic laxatives?

Answer 7

They pull water into the colonic lumen, and thus stimulate peristalsis.

Milk of magnesia
Phosphate enemas
Polyethylene glycol (PEG)
Lactulose (which gets metabolized by colonic bacteria into disaccharides that then pull water into the lumen)

Question 8

Bisacodyl, castor oil, and senna are examples of _____________.

Answer 8

irritant laxatives that stimulate peristalsis

Question 9

True or false: docusate (Colace) is the preferred treatment for CV patients with constipation.

Answer 9

False. It can prevent constipation in pregnant women, CV patients, and hernia patients, but it is not a curative agent for constipation.

Question 10

True or false: magnesium-containing antacids can cause constipation.

Answer 10

False.

Question 11

All of the magnesium-containing laxatives work by ____________.

Answer 11

osmosis

Question 12

What is EHEC?

Answer 12

Enterohemorrhagic Escherichia coli

Question 13

What is the mechanism of ondansetron?

Answer 13

It blocks 5HT3 serotonin receptors in the CTZ, solitary nucleus, and visceral afferents.

Question 14

The most serious side effect of 5HT3 antagonists is ____________.

Answer 14

QT prolongation

Question 15

One example of a class III controlled anti-emetic that can lead to euphoria is ____________.

Answer 15

dronabinol

Question 16

What is one of the biggest concerns with overuse of osmotic laxatives?

Answer 16

Electrolyte depletion

Question 17

You just ordered a medication that gets activated by colonic bacteria and increases osmolarity. What is it?

Answer 17

Lactulose

Question 18

___________ is often given with atropine, called Lomotil.

Answer 18

Diphenoxylate (a partial opioid agonist)

Question 19

Low-dose tricyclic antidepressants are given to those with ______________.

Answer 19

irritable bowel syndrome

Question 20

How does tegaserod work?

Answer 20

It stimulates 5HT4 receptors, leading to peristalsis.

Question 21

A woman with nausea and vomiting comes to your office. She is in her first trimester. What drug can she take for the nausea and vomiting?

Answer 21

First: pyridoxine and H1 antagonist
Second: add D2 antagonist
Finally (for life-threatening dehydration): 5HT3 antagonist

Question 22

Which cardiac medication can cause diarrhea?

Answer 22

Digoxin

Question 23

True or false: activated charcoal can absorb drugs given IV.

Answer 23

True!

Question 24

____________ is useful in treating constipation and diarrhea.

Answer 24

Polycarbophil

Question 25

Avoid the use of bismuth in ______________.

Answer 25

children under 12