A.36.Antiemetic agents. prokinetic agents. drugs for IBS

Question 1

list the group of antiemetic agents

Answer 1

1. H₁ histamine blockers
2. Antimuscarinic agents
3. 5-HT₃ receptor blockers
4. D₂ dopamine receptor blocker
5. NK₁ receptor antagonists
6. CB₁ cannabinoid agonist

Question 2

what is Dimenhydrinate?

Answer 2

H₁ histamine blocker
a combination drug of diphenhydramine and theophylline derivative (reduce sedative effects and abuse liability due to H₁ blockade)

Question 3

what is the function of Dimenhydrinate and scopolamine as antiemetic agents?

Answer 3

inhibits muscarinic receptors in the vomiting center–> inhibitory effect on the emetic pathway

*in addition to the central and peripheral H₁ blockade effect of dimenhydrinate

Question 4

how is Dimenhydrinate given?

Answer 4

oral or parenteral

Question 5

what are the indications for Dimenhydrinate?

Answer 5

motion sickness, Meniere’s disease (vestibular nausea)

antiemetic (chemotherapy-induced)

Question 6

when do we give scopolamine?

Answer 6

motion sickness (vestibular nausea)

Question 7

what is scopolamine?

Answer 7

antimuscarinic agent

Question 8

What is Ondansetron and Palonosetron?

Answer 8

5-HT₃ receptor blockers

Question 9

how is Ondansetron given?

Answer 9

oral or IV

Question 10

how is Palonosteron given?

Answer 10

IV

Question 11

what are the side effects of Dimenhydrinate?

Answer 11

CNS effects
atropine-like effects
𝝰-blockade (orthostatic hypotension)
abuse liability

Question 12

which antiemetic agents are the most potent?

Answer 12

5-HT₃ receptor blockers (Ondansetron)

Question 13

what is the duration of action of Ondansetron and Palonosetron?

Answer 13

3-6 hours

Question 14

what are the indications for giving Ondansetron and Palonosetron?

Answer 14

chemotherapy-induced nausea and vomiting

post-operative nausea and vomiting

Question 15

side effects of Ondansetron and Palonosetron

Answer 15

constipation
QT prolongation, arrhythmias
serotonin syn. (milder risk than SSRI’s and TCA’s)

Question 16

what is the function of 5-HT₃ receptor blockers?

Answer 16

block serotonin receptors (excitatory) in the chemoreceptor trigger zone and enteric nervous system

Question 17

what is the T1/2 of palonosetron?

Answer 17

long

40 hours

Question 18

what are Metoclopramide and Droperidol?

Answer 18

D₂ dopamine receptor blockers

Question 19

how are Metoclopramide and Droperidol given?

Answer 19

oral or parenterally

Question 20

which D₂ dopamine receptor blocker is both an antiemetic and prokinetic agent?

Answer 20

metoclopramide

Question 21

what is the function of D₂ dopamine receptor blockers?

Answer 21

central effects–> inhibition of dopamine D₂-receptor in the chemoreceptor trigger zone (area postrema)–> anti-nausea and antiemetic action
peripheral effects–> in the GI, dopamine acts as an inhibitor of Ach release–> ↓ this inhibition causes a prokinetic effect

Question 22

what are the side effects of Metoclopramide?

Answer 22

CNS effects: restlessness, drowsiness, insomnia
extrapyramidal symptoms (drug-induced parkinsonism)
hyperprolactinemia -galactorrhea, gynecomastia, impotence

Question 23

what are the side effects of droperidol?

Answer 23

CNS depression (additive effect)
𝝰-blockade (orthostatic hypotension)

Question 24

what are the indications of droperidol?

Answer 24

antiemetic (used in surgical and diagnostic procedures)

*also antipsychotic agent-similar to haloperidol

Question 25

what is Aprepitant?

Answer 25

NK₁ receptor antagonist

Question 26

what is the function of Aprepitant

Answer 26

blocks neurokinin receptors in the spinal cord and area postrema–> blocking pain-induced vomiting

Question 27

how is Aprepitant given?

Answer 27

orally

Question 28

what are the indications for Aprepitant

Answer 28

chemotherapy induces nausea and vomiting

post-operative nausea and vomiting

Question 29

Aprepitant is usually given in combination with

Answer 29

dexamethasone and palonosetron

Question 30

side effects of Aprepitant

Answer 30

fatigue, dizziness

diarrhea

Question 31

Aprepitant is an inhibitor of..?

Answer 31

cytochrome P450

Question 32

what is Dronabinol?

Answer 32

CB₁ cannabinoid agonist

Question 33

what is the function of a CB₁ cannabinoid agonist?

Answer 33

inhibitory CB receptors, act to inhibit the presynaptic release of dopamine

Question 34

what are the indications for Dronabinol?

Answer 34

chemotherapy-induced nausea and vomiting

AIDS wasting syndrome (appetite stimulant)

Question 35

side effects of Dronabinol

Answer 35

tachycardia, hypotension
hallucination
reddening of the conjunctiva

Question 36

what is the commonly used combination drug regimen for chemotherapy-induced nausea and vomiting?

Answer 36

Aprepitant
Ondansetron
Dexamethasone

Question 37

what are prokinetic agents?

Answer 37

drugs that selectively stimulate gut motor function

Question 38

when are prokinetic agents contraindicated?

Answer 38

suspected obstructive ileus

Question 39

indications for metoclopramide

Answer 39

GERD (↑ lower esophageal sphincter tone)
conditions with delayed gastric emptying (post-operative, diabetic gastroparesis)
non-ulcer (chronic) dyspepsia 
anti-emetics 
preparation of upper GI endoscopy 
post-partum lactation stimulation

Question 40

list the prokinetic agents

Answer 40

1. metoclopramide- D₂ dopamine receptor blocker
2. Erythromycin-macrolide antibiotics
3. neostigmine -cholinomimetics

Question 41

what is the function of erythromycin as a prokinetic agent

Answer 41

directly stimulates motilin receptors on GI smooth muscle cells

Question 42

prokinetic indications of giving erythromycin

Answer 42

gastroparesis

preparation to upper GI endoscopy

Question 43

what are the side effects of erythromycin

Answer 43

GI symptoms
skin rash
eosinophilia
QT prolongation

Question 44

prokinetic indication of Neostigmine

Answer 44

postoperative ileus